CA2911097C - A microorganism of the family teratosphaeriaceae and methods of using the microorganism to solidify rare earth elements - Google Patents
A microorganism of the family teratosphaeriaceae and methods of using the microorganism to solidify rare earth elements Download PDFInfo
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- CA2911097C CA2911097C CA2911097A CA2911097A CA2911097C CA 2911097 C CA2911097 C CA 2911097C CA 2911097 A CA2911097 A CA 2911097A CA 2911097 A CA2911097 A CA 2911097A CA 2911097 C CA2911097 C CA 2911097C
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- rare earth
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- earth elements
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
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Abstract
The present invention provides a microorganism of the family teratosphaeriaceae and a method of using the microorganism to solidify rare earth elements contained in low-grade mine waste or the like. It further provides a method for recovering rare earth elements having high resource values using the microorganism of the family teratosphaeriaceae. The disclosure further relates to a microorganism of the family teratosphaeriaceae or microorganism mixture containing a microorganism of the family teratosphaeriaceae, which is capable of leaching rare earth elements from a rarc carth cicmcnt-containing mineral or rare carth cicmcnt-containing wastc product.
Description
Description Title of Invention: A MICROORGANISM OF THE FAMILY
MIRCROORGANISM TO SOLIDIFY RARE EARTH ELEMENTS
Technical Field [0001]
The present invention relates to a microorganism capable of leaching rare earth elements and a method for leaching rare earth elements using the microorganism. The present invention further relates to a microorganism capable of solidifying rare earth elements and a method for solidifying rare earth elements using the microorganism.
Background Art
MIRCROORGANISM TO SOLIDIFY RARE EARTH ELEMENTS
Technical Field [0001]
The present invention relates to a microorganism capable of leaching rare earth elements and a method for leaching rare earth elements using the microorganism. The present invention further relates to a microorganism capable of solidifying rare earth elements and a method for solidifying rare earth elements using the microorganism.
Background Art
[0002]
The term "rare earth element" collectively refers to scandium (Sc) having an atomic number of 21 and yttrium (Y) having an atomic number of 39 in Group 3 in the periodic table and an element group consisting of 15 elements having atomic numbers of 57 to 71 which are referred to as lanthanoids. Rare earth elements have an atomic structure with a particular electron orbit and thus have properties such as fluorescence, magnetism, and superconductivity at high temperatures. Therefore, rare earth elements are essential metals in the Japanese industry, which are used for fluorescent materials, permanent magnets, and superconductive materials.
The term "rare earth element" collectively refers to scandium (Sc) having an atomic number of 21 and yttrium (Y) having an atomic number of 39 in Group 3 in the periodic table and an element group consisting of 15 elements having atomic numbers of 57 to 71 which are referred to as lanthanoids. Rare earth elements have an atomic structure with a particular electron orbit and thus have properties such as fluorescence, magnetism, and superconductivity at high temperatures. Therefore, rare earth elements are essential metals in the Japanese industry, which are used for fluorescent materials, permanent magnets, and superconductive materials.
[0003]
Rare earth elements and particularly scandium (Sc) are widely spread in the earth crust, which means that there is no major rare earth element deposit. Usually, rare earth elements are produced as by-products of 23973771.1 Date Recue/Date Received 2020-09-09 uranium or tungsten smelting in the form of oxide. Rare earth elements are produced in small amounts and thus expensive. Therefore, the use of rare earth elements is limited. However, since they have high reactivity, the use thereof for new materials is being under consideration. For example, they are expected to be used for metal halide lamps, added to alloy materials, or = contained in rechargeable batteries, etc. As described above, scandium (Sc) is a rare earth element having a high resource value and thus there actually is a high demand for scandium (Sc) in the business industry. For such reasons, although scandium (Sc) is a low-grade rare earth element among rare earth elements, it is desirable to recover scandium (Sc) even from waste to secure the production.
Conventionally, scandium (Sc) recovery technology is performed by physicochemical treatment. However, such technology is considered problematic due to high cost and a large environmental burden as well as poor recovery efficiency and specificity.
Rare earth elements and particularly scandium (Sc) are widely spread in the earth crust, which means that there is no major rare earth element deposit. Usually, rare earth elements are produced as by-products of 23973771.1 Date Recue/Date Received 2020-09-09 uranium or tungsten smelting in the form of oxide. Rare earth elements are produced in small amounts and thus expensive. Therefore, the use of rare earth elements is limited. However, since they have high reactivity, the use thereof for new materials is being under consideration. For example, they are expected to be used for metal halide lamps, added to alloy materials, or = contained in rechargeable batteries, etc. As described above, scandium (Sc) is a rare earth element having a high resource value and thus there actually is a high demand for scandium (Sc) in the business industry. For such reasons, although scandium (Sc) is a low-grade rare earth element among rare earth elements, it is desirable to recover scandium (Sc) even from waste to secure the production.
Conventionally, scandium (Sc) recovery technology is performed by physicochemical treatment. However, such technology is considered problematic due to high cost and a large environmental burden as well as poor recovery efficiency and specificity.
[0004]
In addition, there is an increasing demand for dysprosium (Dy) as a material for heat-resistant powerful magnets, namely, "heat-resistant neodymium (Nd) magnets." There are a limited number of Dy-producing countries. In addition, due to the influence of environment protection measures, etc., the export price of dysprosium (Dy) has been increasing.
Further, Nd magnets are used as motors in next-generation vehicles, mobile phones, and personal computers. The annual production of dysprosium (Dy) in Japan is approximately 16,000 tons. There is an attempt to recycle 5,600 tons of grinding sludge discarded during the production step by physicochemical treatment. However, rare earth elements cannot be completely recovered by physicochemical methods. Therefore, there is a wish to recover rare earth elements remaining in waste.
In addition, there is an increasing demand for dysprosium (Dy) as a material for heat-resistant powerful magnets, namely, "heat-resistant neodymium (Nd) magnets." There are a limited number of Dy-producing countries. In addition, due to the influence of environment protection measures, etc., the export price of dysprosium (Dy) has been increasing.
Further, Nd magnets are used as motors in next-generation vehicles, mobile phones, and personal computers. The annual production of dysprosium (Dy) in Japan is approximately 16,000 tons. There is an attempt to recycle 5,600 tons of grinding sludge discarded during the production step by physicochemical treatment. However, rare earth elements cannot be completely recovered by physicochemical methods. Therefore, there is a wish to recover rare earth elements remaining in waste.
[0005]
As is apparent from its name "rare earth element," the abundance of rare earth elements on the earth is small. In addition, the market prices of some rare earth elements are very expensive because it is industrially difficult to obtain purely purified substances thereof. However, since the contents of rare earth elements in products are very small, recovery and recycling of rare earth elements have not been widely carried out in consideration of cost.
The current situation in which rare earth elements are discarded means a large loss of resources. Also, there is concern about resource depletion in the future. In addition, while the consumption of rare metals in the leading-edge industry has been sharply increasing, the current situation of rare metal supply has always been unstable because, for example, the rare metal exporters are controlling the rare earth element export due to resource nationalism.
As is apparent from its name "rare earth element," the abundance of rare earth elements on the earth is small. In addition, the market prices of some rare earth elements are very expensive because it is industrially difficult to obtain purely purified substances thereof. However, since the contents of rare earth elements in products are very small, recovery and recycling of rare earth elements have not been widely carried out in consideration of cost.
The current situation in which rare earth elements are discarded means a large loss of resources. Also, there is concern about resource depletion in the future. In addition, while the consumption of rare metals in the leading-edge industry has been sharply increasing, the current situation of rare metal supply has always been unstable because, for example, the rare metal exporters are controlling the rare earth element export due to resource nationalism.
[0006]
As means for recovering useful metal concentrates, biomineralization with the use of metal-metabolizing microorganisms has been widely studied.
A representative example of biomineralization is recovery of noble metals such as palladium (Pd) using Shewanella algae that is a metal ion-reducing bacterium (Non Patent Literature I). This study is intended to use resting cells of a microorganism as reaction sites and solidify dissolved noble metal ions in the periplasm domains of the cells so as to recover noble metal particles. In the case of such recovery of useful elements with the use of biological reaction of microorganisms, the reaction proceeds at ordinary temperature and ordinary pressure, unlike the conventional physicochemical techniques. Therefore, the recovery will lead to the development of energy-saving and cost-efficient recycle process.
Citation List Non Patent Literature
As means for recovering useful metal concentrates, biomineralization with the use of metal-metabolizing microorganisms has been widely studied.
A representative example of biomineralization is recovery of noble metals such as palladium (Pd) using Shewanella algae that is a metal ion-reducing bacterium (Non Patent Literature I). This study is intended to use resting cells of a microorganism as reaction sites and solidify dissolved noble metal ions in the periplasm domains of the cells so as to recover noble metal particles. In the case of such recovery of useful elements with the use of biological reaction of microorganisms, the reaction proceeds at ordinary temperature and ordinary pressure, unlike the conventional physicochemical techniques. Therefore, the recovery will lead to the development of energy-saving and cost-efficient recycle process.
Citation List Non Patent Literature
[0007]
[Non Patent Literature 1]
KAGAKU KOGAKU RONBUNSHU, vol. 36 (3), 288-292, 2010-07-20, the Society of Chemical Engineers, Japan, ''Reduction/Recovery of Palladium by Metal Ion-Reducing Bacterium Shewanella algae'' Summary of Invention Technical Problem
[Non Patent Literature 1]
KAGAKU KOGAKU RONBUNSHU, vol. 36 (3), 288-292, 2010-07-20, the Society of Chemical Engineers, Japan, ''Reduction/Recovery of Palladium by Metal Ion-Reducing Bacterium Shewanella algae'' Summary of Invention Technical Problem
[0008]
Recently, the importance of environment protection and the resource recycling society has been emphasized. Under such circumstances, metal metabolism by microorganisms has been gaining attention as one form of the development of technology. Known examples of metal metabolism by microorganisms include conversion of metals to elements through specific respiration such as denitrification and selective concentration/accumulation of metals in microorganisms. There has been an attempt to use such function of metal metabolism for bacterial leaching or the like in mineral collection for many years. However, no industrial technique has been established yet.
This is because, in addition to the problem of cost, etc., the elucidation of the functions of microorganisms to be used and the development of a follow-up system for the functions have not been sufficiently carried out.
Recently, the importance of environment protection and the resource recycling society has been emphasized. Under such circumstances, metal metabolism by microorganisms has been gaining attention as one form of the development of technology. Known examples of metal metabolism by microorganisms include conversion of metals to elements through specific respiration such as denitrification and selective concentration/accumulation of metals in microorganisms. There has been an attempt to use such function of metal metabolism for bacterial leaching or the like in mineral collection for many years. However, no industrial technique has been established yet.
This is because, in addition to the problem of cost, etc., the elucidation of the functions of microorganisms to be used and the development of a follow-up system for the functions have not been sufficiently carried out.
[0009]
The object of the present invention is to obtain a microorganism capable of selectively leaching rare earth elements and particularly scandium (Sc) contained in low-grade mine waste and the like and to provide a method for recovering rare earth elements and particularly scandium (Sc) having high resource values using the microorganism. Another object of the present invention is to identify a novel microorganism capable of solidifying rare earth elements and to provide a method for solidifying rare earth elements using the microorganism.
Solution to Problem
The object of the present invention is to obtain a microorganism capable of selectively leaching rare earth elements and particularly scandium (Sc) contained in low-grade mine waste and the like and to provide a method for recovering rare earth elements and particularly scandium (Sc) having high resource values using the microorganism. Another object of the present invention is to identify a novel microorganism capable of solidifying rare earth elements and to provide a method for solidifying rare earth elements using the microorganism.
Solution to Problem
[0010]
=
In order to achieve the above objects, the present inventors succeeded in separating a novel microorganism capable of selectively leaching rare earth elements and particularly scandium (Sc) contained in low-grade mine waste or the like from environmental samples. This has led to the completion of the present invention. More specifically, as described in the Examples below, the following findings (a) to (d) were obtained. Thus, the present invention has been completed.
=
In order to achieve the above objects, the present inventors succeeded in separating a novel microorganism capable of selectively leaching rare earth elements and particularly scandium (Sc) contained in low-grade mine waste or the like from environmental samples. This has led to the completion of the present invention. More specifically, as described in the Examples below, the following findings (a) to (d) were obtained. Thus, the present invention has been completed.
[0011]
(a) Breeding of novel microorganisms capable of extracting rare earth elements The S20 bacterial group of microorganisms capable of extracting rare earth elements, which were separated from environmental samples in an acid lake, showed rare earth element-metabolizing capacity in extraction tests using various rare earth element-containing waste products. The S20 bacterial group was able to extract 40% of scandium (Sc) from a scandium (Sc)-containing mineral and 50% of scandium (Sc) from a scandium (Sc)-containing waste product in the flask scale. In addition, dysprosium (Dy) (approximately 70%), neodymium (Nd) (approximately 55%), and praseodymium (Pr) (approximately 65%) were extracted from a rare earth-containing waste product on day 1 of culture, while substantially no iron (Fe) was extracted. These results revealed that the S20 bacterial group has a feature of extracting rare earths ranging from light rare earths such as scandium (Sc) to medium rare earths such as praseodymium (Pr), neodymium (Nd), and dysprosium (Dy) from a plurality of minerals and waste products containing rare earth elements.
(a) Breeding of novel microorganisms capable of extracting rare earth elements The S20 bacterial group of microorganisms capable of extracting rare earth elements, which were separated from environmental samples in an acid lake, showed rare earth element-metabolizing capacity in extraction tests using various rare earth element-containing waste products. The S20 bacterial group was able to extract 40% of scandium (Sc) from a scandium (Sc)-containing mineral and 50% of scandium (Sc) from a scandium (Sc)-containing waste product in the flask scale. In addition, dysprosium (Dy) (approximately 70%), neodymium (Nd) (approximately 55%), and praseodymium (Pr) (approximately 65%) were extracted from a rare earth-containing waste product on day 1 of culture, while substantially no iron (Fe) was extracted. These results revealed that the S20 bacterial group has a feature of extracting rare earths ranging from light rare earths such as scandium (Sc) to medium rare earths such as praseodymium (Pr), neodymium (Nd), and dysprosium (Dy) from a plurality of minerals and waste products containing rare earth elements.
[0012]
(b) The removal of rare earth elements from waste or the like and the development of a recovery reactor As a result of a scandium (Sc) extraction test using the S20 bacterial group in a 5-L tank, 44% of scandium (Sc) and 77% of scandium (Sc) were successfully extracted from a low-grade scandium (Sc)-containing mineral and a low-grade scandium (Sc)-containing waste product, respectively. In addition, as a result of scaling-up to a 5-L tank, the rate of Sc extraction using the S20 bacterial group increased to a level greater than that in the case of the flask scale. Scaling-up from the 100-mL flask to the tank with a volume 60 times that of the flask was successfully achieved for scandium (Sc) extraction using the S20 bacterial group.
(b) The removal of rare earth elements from waste or the like and the development of a recovery reactor As a result of a scandium (Sc) extraction test using the S20 bacterial group in a 5-L tank, 44% of scandium (Sc) and 77% of scandium (Sc) were successfully extracted from a low-grade scandium (Sc)-containing mineral and a low-grade scandium (Sc)-containing waste product, respectively. In addition, as a result of scaling-up to a 5-L tank, the rate of Sc extraction using the S20 bacterial group increased to a level greater than that in the case of the flask scale. Scaling-up from the 100-mL flask to the tank with a volume 60 times that of the flask was successfully achieved for scandium (Sc) extraction using the S20 bacterial group.
[0013]
(c) Establishment of a method for selectively separating/concentrating scandium (Sc) from a liquid extract of bioleached scandium (Sc) A method for selectively separating/concentrating scandium (Sc) from a liquid extract of bioleached scandium (Sc) extracted using the S20 bacterial group was investigated. As a result, 100% recovery of a scandium (Sc) precipitate was successfully achieved by the method using ammonia water.
The scandium (Sc) concentration of the obtained Sc concentrate was approximately 100 times that of the liquid extract of bioleached scandium (Sc). It was also revealed that scandium (Sc) was localized with calcium (Ca) in the precipitate.
(c) Establishment of a method for selectively separating/concentrating scandium (Sc) from a liquid extract of bioleached scandium (Sc) A method for selectively separating/concentrating scandium (Sc) from a liquid extract of bioleached scandium (Sc) extracted using the S20 bacterial group was investigated. As a result, 100% recovery of a scandium (Sc) precipitate was successfully achieved by the method using ammonia water.
The scandium (Sc) concentration of the obtained Sc concentrate was approximately 100 times that of the liquid extract of bioleached scandium (Sc). It was also revealed that scandium (Sc) was localized with calcium (Ca) in the precipitate.
[0014]
(d) Recovery of rare earth elements from an extract of a bioleached element using ammonium bicarbonate It was attempt to concentrate/recover a rare earth element from a liquid extract of bioleached scandium (Sc) and a liquid extract of bioleached rare earth elements extracted by the S20 bacterial group with the use of ammonium bicarbonate. As a result, Sc was successfully concentrated approximately 400-fold and recovered from the liquid extract of bioleached scandium (Sc).
In addition, dysprosium (Dy) and praseodymium (Pr) were successfully concentrated approximately 160-fold and recovered from the liquid extract of bioleached rare earth elements, and neodymium (Nd) was also successfully concentrated approximately 170-fold and recovered from the same.
(d) Recovery of rare earth elements from an extract of a bioleached element using ammonium bicarbonate It was attempt to concentrate/recover a rare earth element from a liquid extract of bioleached scandium (Sc) and a liquid extract of bioleached rare earth elements extracted by the S20 bacterial group with the use of ammonium bicarbonate. As a result, Sc was successfully concentrated approximately 400-fold and recovered from the liquid extract of bioleached scandium (Sc).
In addition, dysprosium (Dy) and praseodymium (Pr) were successfully concentrated approximately 160-fold and recovered from the liquid extract of bioleached rare earth elements, and neodymium (Nd) was also successfully concentrated approximately 170-fold and recovered from the same.
[0015]
Further, in order to achieve the above objects, the present inventors separated novel microorganisms from environmental samples, the microorganisms being capable of solidifying/concentrating dysprosium (Dy) in a specific manner from a dysprosium (Dy)-containing solution. The present inventors also conducted a rare metal metabolism activity test to .
screen for a microorganism having the activity, and carried out genetic analysis, taxonomical identification, and rare metal metabolism activity analysis of the microorganism. This has led to the completion of the present invention.
Further, in order to achieve the above objects, the present inventors separated novel microorganisms from environmental samples, the microorganisms being capable of solidifying/concentrating dysprosium (Dy) in a specific manner from a dysprosium (Dy)-containing solution. The present inventors also conducted a rare metal metabolism activity test to .
screen for a microorganism having the activity, and carried out genetic analysis, taxonomical identification, and rare metal metabolism activity analysis of the microorganism. This has led to the completion of the present invention.
[0016]
The present invention relates to the following embodiments.
(1) A microorganism or microorganism mixture which is capable of leaching a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product.
(2) The microorganism or microorganism mixture according to (1), wherein the rare earth element is at least one selected from the group consisting of scandium (Sc), praseodymium (Pr), neodymium (Nd), and dysprosium (Dy).
(3) The microorganism or microorganism mixture according to (1) or (2), which is a microorganism belonging to the genus Acidithiobacillus or a microorganism mixture comprising microorganisms belonging to the genus Acidithiobacillus.
(4) The microorganism or microorganism mixture according to any one of (1) to (3), which is a microorganism belonging to Acidithiobacillus albertesis or a microorganism mixture comprising microorganisms belonging to Acidithiobacillus albertesis.
(5) A microorganism, which has accession no. NITE BP-01592.
(6) A microorganism mixture which is capable of leaching a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product, comprising a microorganism having accession no. NITE
BP-01592.
The present invention relates to the following embodiments.
(1) A microorganism or microorganism mixture which is capable of leaching a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product.
(2) The microorganism or microorganism mixture according to (1), wherein the rare earth element is at least one selected from the group consisting of scandium (Sc), praseodymium (Pr), neodymium (Nd), and dysprosium (Dy).
(3) The microorganism or microorganism mixture according to (1) or (2), which is a microorganism belonging to the genus Acidithiobacillus or a microorganism mixture comprising microorganisms belonging to the genus Acidithiobacillus.
(4) The microorganism or microorganism mixture according to any one of (1) to (3), which is a microorganism belonging to Acidithiobacillus albertesis or a microorganism mixture comprising microorganisms belonging to Acidithiobacillus albertesis.
(5) A microorganism, which has accession no. NITE BP-01592.
(6) A microorganism mixture which is capable of leaching a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product, comprising a microorganism having accession no. NITE
BP-01592.
[0017]
(7)A method for leaching a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product, comprising the step of treating the rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture according to any one of (1) to (6).
(8) The method according to (7), wherein the rare earth element is at least one selected from the group consisting of scandium (Sc), praseodymium (Pr), neodymium (Nd), and dysprosium (Dy).
(9) A method for recovering a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product, comprising the steps of:
treating the rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture according to any one of (1) to (6); and recovering the rare earth element leached in the above step.
(10) The method according to (9), wherein the rare earth element is at least one selected from the group consisting of scandium (Sc), praseodymium (Pr), neodymium (Nd), and dysprosium (Dy).
(11) The method according to (9) or (10), wherein the rare earth element is recovered by recovering a precipitate generated by adding ammonium bicarbonate or ammonia water to an extract obtained in the step of treating the rare earth element-containing mineral or rare earth element-containing waste with the microorganism or microorganism mixture according to any one of (1) to (6).
(7)A method for leaching a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product, comprising the step of treating the rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture according to any one of (1) to (6).
(8) The method according to (7), wherein the rare earth element is at least one selected from the group consisting of scandium (Sc), praseodymium (Pr), neodymium (Nd), and dysprosium (Dy).
(9) A method for recovering a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product, comprising the steps of:
treating the rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture according to any one of (1) to (6); and recovering the rare earth element leached in the above step.
(10) The method according to (9), wherein the rare earth element is at least one selected from the group consisting of scandium (Sc), praseodymium (Pr), neodymium (Nd), and dysprosium (Dy).
(11) The method according to (9) or (10), wherein the rare earth element is recovered by recovering a precipitate generated by adding ammonium bicarbonate or ammonia water to an extract obtained in the step of treating the rare earth element-containing mineral or rare earth element-containing waste with the microorganism or microorganism mixture according to any one of (1) to (6).
[0018]
(12) A microorganism, which is capable of solidifying a rare earth element.
(13) The microorganism according to (12), which is capable of solidifying at least one rare earth element selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
(14) The microorganism according to (12) or (13), which is capable of solidifying all of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
(15) The microorganism according to any one of (12) to (14), which belongs to the family Teratosphaeriaceae.
(16) The microorganism according to (15), which has scientific features of forming black colonies, having a rod-like shape 10 jim in long diameter and 2 pm in short diameter, being in the form of spherical spores 1 jam in diameter, and growing at an optimal pII of 2 to 4.
(17) A microorganism, which has accession no, NITE BP-01593.
(12) A microorganism, which is capable of solidifying a rare earth element.
(13) The microorganism according to (12), which is capable of solidifying at least one rare earth element selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
(14) The microorganism according to (12) or (13), which is capable of solidifying all of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
(15) The microorganism according to any one of (12) to (14), which belongs to the family Teratosphaeriaceae.
(16) The microorganism according to (15), which has scientific features of forming black colonies, having a rod-like shape 10 jim in long diameter and 2 pm in short diameter, being in the form of spherical spores 1 jam in diameter, and growing at an optimal pII of 2 to 4.
(17) A microorganism, which has accession no, NITE BP-01593.
[0019]
(18) A method for solidifying a rare earth element, comprising the step of culturing the microorganism according to any one of (12) to (17) in a solution containing rare earth elements.
(19) The method according to (18), wherein the rare earth element is at least one selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
(18) A method for solidifying a rare earth element, comprising the step of culturing the microorganism according to any one of (12) to (17) in a solution containing rare earth elements.
(19) The method according to (18), wherein the rare earth element is at least one selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
(20) The method according to (18) or (19), wherein the rare earth element is dysprosium (Dy).
(21) The method according to any one of (18) to (20), wherein the microorganism according to any one of (12) to (17) is cultured in the solution containing rare earth elements under the presence of phosphoric acid.
(22) A method for recovering a rare earth element in a solution, comprising the steps of:
solidifying a rare earth element by culturing the microorganism according to any one of (12) to (17) in a solution containing rare earth elements; and recovering the rare earth element solidified in the above step.
solidifying a rare earth element by culturing the microorganism according to any one of (12) to (17) in a solution containing rare earth elements; and recovering the rare earth element solidified in the above step.
(23) The method according to (22), wherein the rare earth element is at least one selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
(24) The method according to (22) or (23), wherein the rare earth element is dysprosium (Dy).
(25) The method according to any one of (22) to (24), wherein the microorganism according to any one of (12) to (17) is cultured in the solution containing rare earth elements under the presence of phosphoric acid.
[0020]
[0020]
(26) A method for recovering a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product, comprising the steps of:
treating the rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture according to any one of (1) to (6); and solidifying the rare earth element by culturing the microorganism according to any one of (12) to (17) in a solution containing the rare earth element leached in the above step.
treating the rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture according to any one of (1) to (6); and solidifying the rare earth element by culturing the microorganism according to any one of (12) to (17) in a solution containing the rare earth element leached in the above step.
(27) The method according to (26), wherein the microorganism according to any one of (12) to (17) is cultured in the solution containing the rare earth element under the presence of phosphoric acid.
(28) The method according to (26) or (27), wherein the rare earth element is at least one selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), dysprosium (Dy), and scandium (Sc).
Advantageous Effects of Invention [0021]
The present invention relates to a novel microorganism or a novel microorganism mixture capable of leaching rare earth elements. Rare earth elements are leached and recovered using the microorganism or microorganism mixture of the present invention such that rare earth elements contained in waste products and mine residues can be recovered and used as resources. Compared with conventional methods, the method for recovering rare earth elements of the present invention is characterized by specificity, reduction of environmental burdens, low cost, recovery from low-grade waste, a wide range of possible applications, a possibility of reducing operation steps, etc. In addition, the microorganism of the present invention is a novel microorganism capable of solidifying rare earth elements. By solidifying rare earth elements using the microorganism of the present invention, rare earth elements contained in waste products and mine residues can be recovered and used as resources.
Brief Description of Drawings [0022]
[Fig. 1] Fig. 1 shows an electron microscope image of the S20 bacterial group.
[Fig. 2] Fig. 2 shows bioleaching of scandium (Sc) from oxidized scandium using the S20 bacterial group (A: Without bacteria; B: S20 bacterial group).
[Fig. 3] Fig. 3 shows bioleaching of scandium (Sc) from a scandium (Sc)-containing mineral using the S20 bacterial group.
[Fig. 4] Fig. 4 shows bioleaching of scandium (Sc) from a scandium (Sc)-containing waste product using the S20 bacterial group.
[Fig. 5] Fig. 5 shows bioleaching of rare earth elements from a rare earth element-containing waste product using the S20 -bacterial group (A: Without bacteria; B: S20 bacterial group).
[Fig. 6] Fig. 6 shows temporal changes in the concentration of scandium (Sc) extracted from a scandium (Sc)-containing mineral using the S20 bacterial group in a 5-L tank.
[Fig. 7] Fig. 7 shows temporal changes in the concentration and pH of scandium (Sc) extracted from a scandium (Sc)-containing waste product using the S20 bacterial group in a 5-L tank.
[Fig. 8] Fig. 8 shows the comparison of the percentage of scandium (Sc) precipitate recovered from a liquid extract of bioleached scandium (Sc) by different precipitation methods.
[Fig. 9] Fig. 9 shows the comparison of the percentage of scandium (Sc) precipitate recovered from a liquid extract of bioleached scandium (Sc) by an ammonia water precipitation method.
[Fig. 10] Fig. 10 shows an electron microscopic image and EDX elemental mapping images of the recovered scandium (Sc) precipitate.
[Fig. 11] Fig. 11 results of a Dy mineralization test.
[Fig. 12] Fig. 12 shows T9 strain colonies.
[Fig. 13] Fig. 13 shows an optical microscope image of the T9 strain.
[Fig. 14] Fig. 14 shows the growth at different pH levels.
[Fig. 15] Fig. 15 shows the molecular phylogenetic tree of Teratosphaeriaceae sp. T9.
[Fig. 16] Fig. 16 shows Dy mineralization by the T9 strain.
[Fig. 17] Fig. 17 shows results of a rare earth element mineralization test using the T9 strain.
[Fig. 18] Fig. 18 shows an electron microscope image and EDX analysis results (mass concentration (%)) of the T9 strain.
[Fig. 19] Fig. 19 shows mapping of elements on bacterial cells of the T9 strain.
[Fig. 20] Fig. 20 shows Dy-metabolizing capacity of the T9 strain under the presence or absence of phosphoric acid (A: No addition of phosphoric acid; B:
Addition of phosphoric acid).
[Fig. 21] Fig. 21 shows changes in Dy-metabolizing capacity of the T9 strain under the presence of phosphoric acid.
[Fig. 22] Fig. 22 shows mineralization from a model waste mixture solution using the T9 strain.
[Fig. 23] Fig. 23 shows results of the leaching percentage on day 6 of culture for leaching using different microorganisms. In the figure, five bars for each metal represent the results obtained for the S20-1 strain alone, the S20 bacterial group, Acidithiobacillus ferooxidans ATCC19859, Acidithiobacillus thiooxidans ATCC19377, and a combination of ilcidithiobacillus ferooxidans ATCC19859 and Acidithiobacillus thiooxidans ATCC19377 in the order from left to right.
[Fig. 24] Fig. 24 shows SEM-EDX analysis results for the T9 strain.
Description of Embodiments [0023]
Embodiments of the present invention are described below.
[0024]
[1] A microorganism or microorganism mixture capable of leaching rare earth elements and a method for leaching rare earth elements The microorganism or microorganism mixture of the present invention is capable of leaching rare earth elements.
Specific examples of rare earth elements include the following 17 types of elements: Sc (scandium), Y (yttrium), La (lanthanum), Cc (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium). The microorganism or microorganism mixture of the present invention is capable of leaching at least one of the above rare earth elements. Preferably, the microorganism or microorganism mixture of the present invention is a microorganism or microorganism mixture capable of leaching at least one selected from the group consisting of Sc (scandium), Pr (praseodymium), Nd (neodymium), and Dy (dysprosium). Particularly preferably, the microorganism or microorganism mixture of the present invention is capable of leaching all of Sc (scandium), Pr (praseodymium), Nd (neodymium), and Dy (dysprosium).
[0025]
According to the present invention, the expression "leaching rare earth elements" means that when a microorganism or microorganism mixture is cultured in medium under the presence of a rare earth element-containing substance, it causes earth elements to be leached in the medium. It is possible to confirm by the method described in the Examples below that the microorganism or microorganism mixture is capable of leaching rare earth elements. Specifically, a rare earth element-containing substance is added to medium for microorganisms, a culture solution containing a microorganism or microorganism mixture is inoculated thereinto, culture is carried out under appropriate conditions, a culture solution is sampled, and the rare earth element concentration is determined. Thus, the capacity to leach rare earth elements can be evaluated. The microorganism or microorganism mixture of the present invention can be isolated and collected by screening of wild-type strains, mutant strains, and the like according to the above method or a method based on the method.
[0026]
The genus of the microorganism of the present invention is not particularly limited. There is a known method for classifying (identifying the species of) a microorganism obtained from an environmental sample or the like based on the information on 16SrRNA, etc. The microorganism used in the present invention may be any microorganism selected from among wild-type strains, mutant strains, and recombinants produced by genetic engineering techniques, etc.
[0027]
Preferably, the microorganism of the present invention is a microoganism belonging to the genus Acidithiobacillus. Examples thereof include microorganisms belonging to Acidithiobacillus albertesis. For example, a microoganism belonging to Acidithiobacillus albertesis is the S20-1 strain which is a bacterium included in the S20 bacterial group isolated in the Examples below. The S20-1 strain has been deposited with accession no. NITE BP-01592 in the Patent Microorganisms Depositary, National Institute of Technology and Evaluation (2-5-8 Kazusakamatari, Kisarazu-shi, Chiba 292-0818, Japan) on April 15, 2013. The S20-I strain is a bacillus having a long diameter of 1 i_tm and a short diameter of 0.5 p.m and a scientific feature of not growing without the addition of sulfur.
[0028]
The microorganism of the present invention may be a microorganism mixture comprising microorganisms of different species as well as a monospecific species. The S20 bacterial group used in the Examples below is a microorganism mixture containing the S20-1 strain. Microorganisms that can be contained in the microorganism mixture of the present invention may be of the same species or different species. The S20 bacterial group is a microorganism mixture comprising different types of microorganisms having different properties. It is therefore considered that the respective microorganisms complement their functions in order to leach rare earth elements so that leaching performance can be improved.
Advantageous Effects of Invention [0021]
The present invention relates to a novel microorganism or a novel microorganism mixture capable of leaching rare earth elements. Rare earth elements are leached and recovered using the microorganism or microorganism mixture of the present invention such that rare earth elements contained in waste products and mine residues can be recovered and used as resources. Compared with conventional methods, the method for recovering rare earth elements of the present invention is characterized by specificity, reduction of environmental burdens, low cost, recovery from low-grade waste, a wide range of possible applications, a possibility of reducing operation steps, etc. In addition, the microorganism of the present invention is a novel microorganism capable of solidifying rare earth elements. By solidifying rare earth elements using the microorganism of the present invention, rare earth elements contained in waste products and mine residues can be recovered and used as resources.
Brief Description of Drawings [0022]
[Fig. 1] Fig. 1 shows an electron microscope image of the S20 bacterial group.
[Fig. 2] Fig. 2 shows bioleaching of scandium (Sc) from oxidized scandium using the S20 bacterial group (A: Without bacteria; B: S20 bacterial group).
[Fig. 3] Fig. 3 shows bioleaching of scandium (Sc) from a scandium (Sc)-containing mineral using the S20 bacterial group.
[Fig. 4] Fig. 4 shows bioleaching of scandium (Sc) from a scandium (Sc)-containing waste product using the S20 bacterial group.
[Fig. 5] Fig. 5 shows bioleaching of rare earth elements from a rare earth element-containing waste product using the S20 -bacterial group (A: Without bacteria; B: S20 bacterial group).
[Fig. 6] Fig. 6 shows temporal changes in the concentration of scandium (Sc) extracted from a scandium (Sc)-containing mineral using the S20 bacterial group in a 5-L tank.
[Fig. 7] Fig. 7 shows temporal changes in the concentration and pH of scandium (Sc) extracted from a scandium (Sc)-containing waste product using the S20 bacterial group in a 5-L tank.
[Fig. 8] Fig. 8 shows the comparison of the percentage of scandium (Sc) precipitate recovered from a liquid extract of bioleached scandium (Sc) by different precipitation methods.
[Fig. 9] Fig. 9 shows the comparison of the percentage of scandium (Sc) precipitate recovered from a liquid extract of bioleached scandium (Sc) by an ammonia water precipitation method.
[Fig. 10] Fig. 10 shows an electron microscopic image and EDX elemental mapping images of the recovered scandium (Sc) precipitate.
[Fig. 11] Fig. 11 results of a Dy mineralization test.
[Fig. 12] Fig. 12 shows T9 strain colonies.
[Fig. 13] Fig. 13 shows an optical microscope image of the T9 strain.
[Fig. 14] Fig. 14 shows the growth at different pH levels.
[Fig. 15] Fig. 15 shows the molecular phylogenetic tree of Teratosphaeriaceae sp. T9.
[Fig. 16] Fig. 16 shows Dy mineralization by the T9 strain.
[Fig. 17] Fig. 17 shows results of a rare earth element mineralization test using the T9 strain.
[Fig. 18] Fig. 18 shows an electron microscope image and EDX analysis results (mass concentration (%)) of the T9 strain.
[Fig. 19] Fig. 19 shows mapping of elements on bacterial cells of the T9 strain.
[Fig. 20] Fig. 20 shows Dy-metabolizing capacity of the T9 strain under the presence or absence of phosphoric acid (A: No addition of phosphoric acid; B:
Addition of phosphoric acid).
[Fig. 21] Fig. 21 shows changes in Dy-metabolizing capacity of the T9 strain under the presence of phosphoric acid.
[Fig. 22] Fig. 22 shows mineralization from a model waste mixture solution using the T9 strain.
[Fig. 23] Fig. 23 shows results of the leaching percentage on day 6 of culture for leaching using different microorganisms. In the figure, five bars for each metal represent the results obtained for the S20-1 strain alone, the S20 bacterial group, Acidithiobacillus ferooxidans ATCC19859, Acidithiobacillus thiooxidans ATCC19377, and a combination of ilcidithiobacillus ferooxidans ATCC19859 and Acidithiobacillus thiooxidans ATCC19377 in the order from left to right.
[Fig. 24] Fig. 24 shows SEM-EDX analysis results for the T9 strain.
Description of Embodiments [0023]
Embodiments of the present invention are described below.
[0024]
[1] A microorganism or microorganism mixture capable of leaching rare earth elements and a method for leaching rare earth elements The microorganism or microorganism mixture of the present invention is capable of leaching rare earth elements.
Specific examples of rare earth elements include the following 17 types of elements: Sc (scandium), Y (yttrium), La (lanthanum), Cc (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium). The microorganism or microorganism mixture of the present invention is capable of leaching at least one of the above rare earth elements. Preferably, the microorganism or microorganism mixture of the present invention is a microorganism or microorganism mixture capable of leaching at least one selected from the group consisting of Sc (scandium), Pr (praseodymium), Nd (neodymium), and Dy (dysprosium). Particularly preferably, the microorganism or microorganism mixture of the present invention is capable of leaching all of Sc (scandium), Pr (praseodymium), Nd (neodymium), and Dy (dysprosium).
[0025]
According to the present invention, the expression "leaching rare earth elements" means that when a microorganism or microorganism mixture is cultured in medium under the presence of a rare earth element-containing substance, it causes earth elements to be leached in the medium. It is possible to confirm by the method described in the Examples below that the microorganism or microorganism mixture is capable of leaching rare earth elements. Specifically, a rare earth element-containing substance is added to medium for microorganisms, a culture solution containing a microorganism or microorganism mixture is inoculated thereinto, culture is carried out under appropriate conditions, a culture solution is sampled, and the rare earth element concentration is determined. Thus, the capacity to leach rare earth elements can be evaluated. The microorganism or microorganism mixture of the present invention can be isolated and collected by screening of wild-type strains, mutant strains, and the like according to the above method or a method based on the method.
[0026]
The genus of the microorganism of the present invention is not particularly limited. There is a known method for classifying (identifying the species of) a microorganism obtained from an environmental sample or the like based on the information on 16SrRNA, etc. The microorganism used in the present invention may be any microorganism selected from among wild-type strains, mutant strains, and recombinants produced by genetic engineering techniques, etc.
[0027]
Preferably, the microorganism of the present invention is a microoganism belonging to the genus Acidithiobacillus. Examples thereof include microorganisms belonging to Acidithiobacillus albertesis. For example, a microoganism belonging to Acidithiobacillus albertesis is the S20-1 strain which is a bacterium included in the S20 bacterial group isolated in the Examples below. The S20-1 strain has been deposited with accession no. NITE BP-01592 in the Patent Microorganisms Depositary, National Institute of Technology and Evaluation (2-5-8 Kazusakamatari, Kisarazu-shi, Chiba 292-0818, Japan) on April 15, 2013. The S20-I strain is a bacillus having a long diameter of 1 i_tm and a short diameter of 0.5 p.m and a scientific feature of not growing without the addition of sulfur.
[0028]
The microorganism of the present invention may be a microorganism mixture comprising microorganisms of different species as well as a monospecific species. The S20 bacterial group used in the Examples below is a microorganism mixture containing the S20-1 strain. Microorganisms that can be contained in the microorganism mixture of the present invention may be of the same species or different species. The S20 bacterial group is a microorganism mixture comprising different types of microorganisms having different properties. It is therefore considered that the respective microorganisms complement their functions in order to leach rare earth elements so that leaching performance can be improved.
[0029]
Further, according to the present invention, a method for leaching rare earth elements, comprising treating a material containing rare earth elements with the microorganism or microorganism mixture of the present invention, is provided. The types of rare earth elements to be leached are not particularly limited; however, they are preferably at least one selected from the group consisting of scandium (Sc), praseodymium (Pr), neodymium (Nd), and dysprosium (Dy), and particularly preferably scandium (Sc).
10030]
A method for culturing the microorganism or microorganism mixture of the present invention is not particularly limited as long as rare earth elements can be leached. Thus, favorable culture conditions can be appropriately selected depending on the properties of microorganisms to be used. For example, in the case of the S20 bacterial group used in the Examples, culture can be carried out in medium at pH 2-4 under aerobic conditions of shaking culture or the like at 25 C to 40 C, preferably 25 C to 3.5 C, and particularly preferably 28 C to 32 C.
[0031]
According to the present invention, rare earth elements can be leached by the above method and then the leached rare earth elements can be recovered. The rare earth elements can be recovered by a known method such as centrifugation, filter filtration, or a combination thereof.
[0032]
Preferably, ammonium bicarbonate or ammonia water is added to an extract obtained by treating a rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture of the present invention and the resulting precipitate is recovered. Thus, rare earth elements can be recovered.
[0033]
It is possible to apply the method of the present invention for leaching rare earth elements to ores, electronic devices, urban waste water, and waste water from mines, factories, etc., which contain rare earth elements.
[0034]
[2] A microorganism capable of solidifying rare earth elements a method for solidifying rare earth elements The microorganism of the present invention is a microorganism capable of solidifying rare earth elements.
Specific examples of rare earth elements include the following 17 elements: Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium). The microorganism of the present invention is capable of solidifying at least one of the above rare earth elements. Preferably, the microorganism of the present invention is a microorganism capable of solidifying at least one rare earth element selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
Particularly preferably, the microorganism of the present invention is capable of solidifying all of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
[0035]
According to the present invention, the term solidification means that rare earth elements dissolved in a solution become insoluble (mineralization).
It is possible to confirm by the method described in the Examples below that the microorganism is capable of solidifying rare earth elements. Specifically, a sample containing microoganisms is inoculated into medium for microorganisms to which a chloride solution of a rare earth element (e.g., a DyCl3 solution) has been added, followed by culture under conditions that allow the growth of the microorganism. Thereafter, the capacity to solidify rare earth elements can be evaluated by determining the concentrations of rare earth elements in the supernatant of a sample obtained by sampling. The microorganism capable of solidifying rare earth elements of the present invention can be isolated and collected by screening of wild-type strains, mutant strains, and the like according to the above method or a method based on the method.
[0036]
The genus of the microoganism capable of solidifying rare earth elements of the present invention is not particularly limited. There is a known method for classifying (identifying the species of) a microorganism obtained from an environmental sample or the like based on the information on 16SrRNA, etc. The microorganism used in the present invention may be any microorganism selected from among wild-type strains, mutant strains, and recombinants produced by genetic engineering techniques, etc.
[0037]
Preferable examples of the microoganism capable of solidifying rare earth elements of the present invention include microorganisms belonging to the families Teratosphaeriaceae, Penidiella, Mycosphaerellaceae, or Dothideales. It has been revealed that microoganisms belonging to the families Teratosphaeriaceae, Penidiella, Mycosphaerellaceae, or Dothideales have at least 95% homology in terms of the nucleotide sequences of 18SrDNA, 28SrDNA-D1/D2, and ITS-5.8SrDNA. As described above, according to the present invention, it is possible to use microorganisms having at least 95%
homology to microorganisms belonging to the family Teratosphaeriaceae in terms of the nucleotide sequences of 18SrDNA, 28SrDNA-D1/D2, and ITS-5.8SrDNA. For example, a microoganism belonging to the family Teratosphaeriaceae is the T9 strain (Teratosphaeriaceae sp. T9) isolated in the Examples below. The 19 strain has been deposited with accession no.
NITE BP-01593 in the Patent Microorganisms Depositary, National Institute of Technology and Evaluation (2-5-8 Kazusakamatari, Kisarazu-shi, Chiba 292-0818, Japan) on April 15, 2013. The T9 strain has scientific features of forming black colonies, having a rod-like shape 10 p.m in long diameter and 2 Ilm in short diameter, being in the form of spherical spores 1 vim in diameter, and growing at an optimal pII of 2 to 4.
[0038]
Further, according to the present invention, a method for solidifying rare earth elements, comprising culturing the microoganism capable of solidifying rare earth elements of the present invention in a solution containing rare earth elements, is provided. The types of rare earth elements to be solidified are not particularly limited; however, they are preferably at least one selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy), and particularly preferably dysprosium (Dy).
[0039]
The method for culturing the microorganism of the present invention is not particularly limited as long as rare earth elements can be solidified.
Preferable culture conditions can be selected depending on the properties of microorganisms to be used. For example, in the case of the T9 strain used in the Examples below, culture can be carried out in medium at pH 2-4 under aerobic conditions of shaking culture or the like at 25 C to 40 C, preferably 25 C to 35 C, and particularly preferably 28 C to 32 C.
[0040]
When culturing the microorganism capable of solidifying rare earth elements of the present invention, culture can be preferably carried out under the presence of phosphoric acid. In some cases, it is possible to improve the capacity to solidify rare earth elements of the microoganism under the presence of phosphoric acid.
[00411 According to the present invention, rare earth elements can be solidified by the above method and then the solidified rare earth elements can be recovered. The rare earth elements can be recovered by a known method such as centrifugation, filter filtration, or a combination thereof.
[0042]
It is possible to apply the method of the present invention for solidifying rare earth elements to ores, electronic devices, urban waste water, and waste water from mines, factories, etc., which contain rare earth elements.
[0043]
[3] A method for leaching and solidifying rare earth elements According to the present invention, rare earth elements may be recovered from a rare earth element-containing mineral or rare earth element-containing waste product by culturing the microorganism capable of solidifying rare earth elements of the present invention in a solution containing rare earth elements leached in the step of treating a rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture capable of leaching rare earth elements of the present invention, thereby solidifying the rare earth elements.
[0044]
The present invention is more specifically described with reference to the Examples below. However, the technical scope of the present invention is not particularly limited to the Examples.
[Examples]
[0045]
Example 1:
(A) Experimental Materials and Method (1) Medium to be used FeSO4 (10 g/L) was added to TSB (Tryptic Soy Broth) (3 g/L) dissolved in ion-exchange water and then 112SO4 was added to adjust the pH to pH 3.0, followed by autoclave sterilization. After sterilization, sulfur (S) (5g/L) was further added. The obtained medium supplemented with sulfur was designated as "TSB+S medium" and used as medium for screening.
[0046]
(2) A method for separating microorganisms for rare earth element leaching TSB+S medium was dispensed into 100-mL Erlenmeyer flasks (50 mL
each) and inoculated with different screening sample suspensions (1 mL each), followed by culture for 7 days under rotary shaking (120 rpm) at 30 C.
Sampling was performed at arbitrary time points for pH measurement.
TSB+S medium which was not inoculated with any of environmental samples and treated under the same conditions was designated as a control. A
decrease in the pH of medium was used as an index of the growth of microorganisms for leaching.
[0047]
(3) A rare earth element bioleaching test using a variety of rare earth element-containing substances TSB+S medium was dispensed into 100-mL Erlenmeyer flasks (50 mL
each) and an arbitrary amount of a rare earth element-containing substance was added to each flask in accordance with the experiment. A day-4 culture solution (0.5 mL) of microorganisms for leaching obtained from each environmental sample was inoculated into the medium, followed by culture under rotary shaking (120 rpm) at 30 C. In addition, the medium which was not inoculated with the bacterial group and treated under the same conditions was designated as a control. Each culture solution was subjected to sampling at arbitrary time points (1 mL each) for the determination of the element concentration.
[0048]
(4) A scale-up test for bioleaching of scandium (Sc) from a scandium (SO-containing mineral using a 5-L tank TSB medium (0.3% (W/V), 3000 mL) was introduced into a 5-L reactor and subjected to autoclave sterilization, followed by aeration stirring at 30 C
pH 3.0, 250 rpm, and 0.33 vvm (1L/min) for 30 minutes. Then, a sulfur powder (30 g) and FeSO4 (30 g) were added. A culture solution of the S20 bacterial group precultured in TSB medium for 4 days (30 mL corresponding to 1% of the total volume) was inoculated into the medium. A scandium (Sc)-containing mineral (30 g) was added to the medium inoculated with the bacterial cells, followed by culture at 30 C, 250 rpm, and 1L/min. The pH in the early stage of culture was adjusted to pH 3Ø Long-term culture was performed, during which TSB medium in an amount equivalent to the amount of evaporated moisture was added every about 30 days. The amount of the evaporated medium was calculated by reading the medium surface position relative to the calibration line on the 5-L tank. Sampling of the measurement sample was performed according to need via a sampling opening. Elemental analysis of the sample was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0049]
(5) A scale-up test for bioleaching of scandium (Sc) from a scandium (Sc)-containing waste product using a 5-L tank TSB medium (0.3% (W/V), 3000 mL) was introduced into a 5-L reactor and subjected to autoclave sterilization, followed by aeration stirring at 30 C
pH 3.0, 250rpm, and 0.33 vvm (1L/min) for 30 minutes. Then, a sulfur powder (30 g) was added. A culture solution of the S20 bacterial group precultured in TSB medium for 4 days (30 mL corresponding to 1% of the total volume) was inoculated into the medium. A scandium (Sc)-containing waste product (300 g) was added to the medium inoculated with the bacterial cells, followed by culture at 30 C, 250 rpm, and 1L/min. The pH in the early stage of culture pH was adjusted to pH 3Ø Sampling of the measurement sample was performed according to need via a sampling opening. Elemental analysis of the sample was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0050]
(6) Investigation of a method for recovering rare earth elements using ammonium bicarbonate 0.5M NH4HCO3 (10% (v/v)) was added to a liquid extract of bioleached rare earth elements, followed by vortex stirring for about 30 seconds. The mixture solution subjected to stirring was centrifuged (20 C, 10,000 prm, 10 minutes) and separated into a supernatant and a precipitate by decantation. 0.5M NH4HCO3 (2 mL) was added to the obtained supernatant and the same operation was repeated. The precipitates obtained by repeating the operation twice were mixed together and dried at 80 C, followed by weight measurement. The resulting dried precipitate was dissolved in aqua regia (1 mL) to obtain an analysis sample. In addition, the supernatant was filtered through a 0.2-lam filter to obtain an analysis sample. Sample analysis was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0051]
(7) Investigation of a method for recovering rare earth elements using oxalic acid A 10% H2C204 solution (0.5 mL) was added to a liquid extract of rare earth elements (4.5 mL) so as to result in a final concentration of 1% (v/v).
Then, an adequate amount of ammonia water was added to adjust the pH to pH
4Ø The resulting solution was vortex stirred for about 30 seconds. The stirred solution was centrifuged (20 C, 10,000 rpm, 10 minutes) and separated into a supernatant and a precipitate by decantation. A 10% H2C204 solution (0.5 mL) was added to the obtained supernatant and the same operation was repeated twice. The precipitates obtained by repeating the recovery operation three times in total were separately dried at 80 C, followed by weight measurement. The resulting dried precipitates were dissolved in aqua regia (1 mL) to obtain analysis samples. In addition, the supernatant was filtered through a 0.2-lam filter to obtain an analysis sample. Sample analysis was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0052]
(8) Investigation of a method for recovering rare earth elements using ammonia water The pH of a liquid extract of rare earth elements (4.5 mL) was adjusted to pH 4.0 or pH 5.0 using ammonia water. The solution was allowed to stand still for about 2 hours at room temperature until a precipitate was formed, followed by centrifugation (10000 rpm, 5 minutes, 20 C). A supernatant and a precipitate were separated using a pipette. The obtained supernatant was filtered through a 0.2-rim filter to obtain an analysis sample. The precipitate was dried (60 C), followed by weight measurement. The dried precipitate was dissolved in ultrapure water or sulfuric acid to obtain an analysis sample.
Sample analysis was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0053]
(9) A method for analyzing the element concentration The samples obtained by sampling were centrifuged (15,000 rpm, 5 minutes, 20 C) and the supernatants thereof were filtered through disc filters (pore size: 0.2 [tm). The filtrates were designated as measurement sample stock solutions.
Each measurement sample stock solution was 1/10-, 1/100-, and 1/1000-diluted with ultrapure water. Dissolved elements in each solution were quantitatively determined using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.). Standard curves were created using standard solutions (SPEX:
XSTC-622, XSTC-1). The concentration range was determined to be between 0.01 mg/L and 1.0 mg/L. Measurement solutions were prepared by serial dilution in the descending order of the concentration. Each measurement solution was adjusted to have the same liquid properties.
Measurement was repeated three times for each sample. The mean value of values with a deviation of 5% or less was designated as a measurement result.
[0054]
(10) Analysis of recovered precipitates by an energy-dispersive x-ray spectrometer A portion of the precipitate obtained by ammonia precipitation was collected for non-destructive analysis. This analysis sample was fixed on an observation table using carbon tape. Observation and surface analysis were carried out using a tabletop electron microscope (TM3000: Hitachi High-Technologies Corporation) and EDX (Quantax70: Bruker AXS
Microanalysis GmbH) in accordance with the protocols.
[0055]
(B) Results and Discussion =
(1) Separation of microorganisms from environmental samples Representative microorganisms involved in bioleaching have a feature of reducing pH in the growth environment. Thus, at first, it was attempted to separate microorganisms capable of reducing medium pH over the course of growth from environmental samples. As a result, an environmental sample whose pH had declined on day 3 of culture was found. A culture solution of the obtained environmental sample was observed by an optical microscope.
Accordingly, several types of microorganisms having different shapes were observed. Next, in order to reconfirm the presence of the microorganisms in the culture solution of the environmental sample, electron microscope observation was carried out. A bacillus having a long diameter of 1 p.m and a short diameter of 0.5 litm was observed in a part of the sample (fig. 1). No pH decline was confirmed for a culture solution to which no environmental sample had been added. Thus, it is considered that this pH decline was caused by microorganism reaction. Based on the above, the bacterial group in the environmental sample was designated as "the S20 bacterial group."
The S20 bacterial group was sampled in sand near water of Yugama lake in the area of Mount Shirane, Kusatsu, Kusatsu Town, Agatsuma District, Gunma, Japan (North latitude: 36 degrees, 38 minutes, and 38 seconds; East longitude:
138 degrees, 31 minutes, and 40 seconds).
[0056]
The properties of the S20 bacterial group (characteristics, culture conditions, appearance during culture) were described below.
According to molecular biological classification, given that the total bacteria in the bacterial group accounts for 100%, the following microorganisms form flora at the corresponding percentages.
Acidithiobacillus albertesis: 99.72%
Acidithiobacillus thiooxidans: 0.02%
Other microorganisms of the genus Acidithiobacillus: 0.15%
Other microorganisms of the phylum Proteobacteria: 0.02%
No identified microorganisms: 0.09%
In addition, the bacterial group includes Acidomyces acidophilus, Acidomyces acidothermus, and the microorganisms of the genus Acidomyces as eukaryotes.
Sulfur powder is necessary for the growth of the S20 bacterial group.
For example, when the S20 bacterial group is cultured in TSB (Tryptic Soy Broth) medium, which is a naturally occurring medium, the medium color changes from milky white to dark green. Sulfur powder having strong hydrophobicity is dissolved in a culture solution with time during culture.
[0057]
Next, a test of scandium (Sc) bioleaching from oxidized scandium was conducted using the S20 bacterial group (fig. 2). As a result, extraction of approximately 100 mg/L scandium (Sc) from the culture solution of the S20 bacterial group was confirmed on day 15 of culture at an extraction percentage of substantially 100%. Therefore, it was determined to use the S20 bacterial group in subsequent tests.
[0058]
(2) Scandium (Sc) bioleaching from a scandium (Sc)-containing mineral using the S20 bacterial group A test of scandium (Sc) bioleaching from a scandium (Sc)-containing mineral (scandium (Sc) concentration: 400 mg/L: 0.5 g/50 mL medium addition) was conducted using the S20 bacterial group. As a result, the scandium (Sc) extraction percentage was approximately 40% on day 42 of culture (fig. 3). This result suggests that the elements extracted from a scandium (Sc)-containing mineral using the S20 bacterial group can be roughly divided into the following two types based on the tendency to be extracted: elements such as Fe, Mg, and Mn that are likely to be extracted;
and elements such as Al that are unlikely to be extracted. It was considered that scandium (Sc) belongs to the group including Fe, Mg, and Mn and is relatively easily extracted from the sample. However, the scandium (Sc) extraction concentration was 1.5 mg/L, which was the lowest level among the major components (table 1).
[0059]
[Table 1]
Table 1: The element concentrations of the liquid extract of Sc obtained from the Sc-containing mineral using the S20 bacterial group (day 42 of culture) Al Mg Mn Ni Sc Ti Fe S20 (mg/L) 31 15 38 1.1 1.5 6.9 3000 Without bacteria (mg/L) 2.7 9.4 15 0.3 0.3 0.1 1700 [0060]
(3) Scandium (Sc) bioleaching from a scandium (Sc)-containing waste product (titanium (Ti) mineral residue) using the S20 bacterial group A waste sample (scandium (Sc) concentration: 40 mg/L: 10 g/50 mL
medium addition) discharged from an actual plant was subjected to a scandium (Sc) bioleaching test using the S20 bacterial group. As a result, the scandium (Sc) extraction percentage on day 15 of culture was 50%. This was the third highest extraction percentage among elements contained in the waste sample (Fig. 4). The scandium (Sc) extraction concentration was 4 mg/L
which was the lowest level among the major components (table 2). Under the conditions without the presence of the S20 bacterial group, substantially no scandium (Sc) was detected. This suggested that the S20 bacterial group causes scandium (Sc) extraction from the waste product (mineral residue).
The extraction percentage (50% on day 15) of the scandium (Sc)-containing waste product (scandium (Sc) concentration: 40 mg/L) was greater than the extraction percentage (40% on day 42) of the above scandium (Sc)-containing mineral (scandium (Sc) concentration: 400 mg/L). Thus, it is considered that the S20 bacterial group can be used for extraction from low-grade waste.
[0061]
[Table 2]
Table 2: The element concentrations of the liquid extract of Sc obtained from the Sc-containing waste product using the S20 bacterial group (day 7 of culture) Ti Fe Al V Ni Zr Mn Sc S20 (mg/L) 12.0 930 150.0 64.0 540 1.0 69.0 4.0 Without bacteria (mg/L) 0.0 0.0 2.0 0.0 220 0.0 54.0 0.0 [0062]
(4) Bioleaching of rare earth elements from a rare earth element-containing waste product using the S20 bacterial group In order to examine extraction specificity of the S20 bacterial group with respect to other rare earth elements, a waste product containing rare earth elements such as dysprosium (Dy), neodymium (Nd), and praseodymium (Pr) (0.5 g/50 ml, medium addition) was subjected to a rare earth element bioleaching test. As a result, approximately 80% or more of dysprosium (Dy) and approximately 70% or more of praseodymium (Pr) and neodymium (Nd) were extracted by day 7 of culture (fig. 5), while on the other hand, only approximately 10% of iron (Fe) was extracted. No iron (Fe) was extracted from day 0 to day 3. It is considered that rare earth elements can be exclusively and selectively obtained by recovering them in the early stage of culture. As described above, it was revealed that the S20 bacterial group has characteristic ability to extract rare earths ranging from light rare earths such as scandium (Sc) to medium rare earths praseodymium (Pr), neodymium (Nd), and dysprosium (Dy) from a mineral or waste product containing a plurality of rare earth elements.
[0063]
(5) Scaling-up of scandium (Sc) bioleaching from a scandium (Sc)-containing mineral Scandium (Sc) bioleaching from a scandium (Sc)-containing mineral was carried out using a 5-L tank to attempt scaling-up from a flask. The extraction concentration in a flask and that in a 5-L tank were compared on day 42 of culture (table 3). As a result, the scandium (Sc) concentration in the flask was 1.5 mg/L, and that in the 5-L tank was 1.6 mg/L. That is, reproducibility of the scandium (Sc) extraction percentage was obtained in the scale-up test. In addition, the extraction concentrations of Mn, Ni, and Ti in the 5-L tank were about twice those in the flask.
[0064]
[Table 3]
Table 3: Comparison of major element concentrations in the liquid extract of Sc obtained from the Sc-containing mineral for each scale (day 42 of culture) Al Mn Ni Sc Ti 5-L tank mg/L 28 61 2.6 1.6 13 100-mL flask mg/L 31 39 1.1 1.5 6.9 [0065]
The amount of extracted scandium (Sc) increased with time. Thus, in order to further improve scandium (Sc) extraction, long-term culture was conducted (fig. 6). As a result, scandium (Sc) extraction was successfully achieved to a level of 3.5 mg/L at a maximum on day 90 of culture.
Eventually, scandium (Sc) extraction was continued up to day 111 of culture and then the extraction was terminated for convenience of the experiment.
However, even in the case of the control which had not been inoculated with bacteria, scandium (Sc) extraction was achieved to a level of I. mg/L at a maximum. This is probably because a bacterium having extraction capacity of the microorganisms adhering to the waste product had grown as a result of long-term culture.
[0066]
(6) Scandium (Sc) bioleaching from a scandium (Sc)-containing waste product Scandium (Sc) bioleaching from a scandium (Sc)-containing waste product was carried out using a 5-L tank to attempt scaling-up from a flask.
The extraction concentration in the flask and that in the 5-L tank were compared on day 7 of culture (table 4). As a result, the scandium (Sc) concentration in the 5-L tank was 7.5 mg/L which was about twice that in the flask (4.0 mg/L). In addition, the extraction concentrations of Al, Fe, Ti, and Zr in the 5-L tank were about 5 to 10 times those in the flask.
[0067]
[Table 4]
Table 4: Temporal changes in the major element concentrations in the liquid extract of Sc obtained from the Sc-containing waste product for each scale (day 7 of culture) Al Fe Ni Sc Ti Zr 5-L tank mg/L 1400 4400 170 7.5 120 4.9 100-mL flask mg/L 150 930 540 4.0 12 1.0 [0068]
Fig. 7 shows temporal changes in the scandium (Sc) extraction percentage and pH. The results show that the scandium (Sc) extraction percentage was approximately 90% on day 9 of culture. In addition, it was found that pH went up and down from day 2 to day 6 of culture while the scandium (Sc) extraction percentage was significantly improved. This suggests a possibility that scandium (Sc) extraction would not depend on pH
and other factors would be involved in the extraction.
[0069]
In consideration of the above, a tank was designed/constructed for the intended use for scaling-up from culture in a flask to culture in a laboratory-scale reactor. Culture was carried out using the tank. As a result, scandium (Sc) was successfully extracted from both of the scandium (Sc)-containing mineral and waste product samples.
[0070]
(7) Analysis of scandium (Sc) carbonate recovered from a liquid extract of bioleached scandium (Sc) using ammonium bicarbonate Table 5 shows the analysis results for a liquid extract of bioleached scandium (Sc) (bioleached rare earth) extracted from a scandium (Sc)-containing waste product using the S20 bacterial group and the analysis results for a carbonate precipitate (12.4 mg) recovered from a liquid extract of bioleached scandium (Sc) (5 int,). As a result of elemental analysis, it was found that scandium (Sc) concentration in the liquid extract was 0.419 mg/L
while the same in the carbonate precipitate was 166 mg/kg, indicating that scandium (Sc) was concentrated approximately 400-fold. In addition, the recovery rate was 98.4%, indicating that substantially all scandium (Sc) was recovered. Meanwhile, the liquid extract of bioleached rare earth elements also contained elements such as aluminum and iron, showing that elements existing in large amounts were concentrated in carbonate and it was possible to recover at least 90% of the elements. It is considered that ammonium bicarbonate caused an increase in pH of the solution to around neutral pH, which resulted in precipitation of elements other than rare earth elements.
[0071]
[Table 5]
Table 5: Elemental analysis results for the liquid extract of bioleached elements and the recovered carbonate precipitate Aluminum Calcium Iron Magnesium Manganese Nickel Scandium Zinc Al Ca Fe Mg Mn Ni Sc Zn Liquid 312 128 457 475 65.9 135 0.419 23.7 extract of bioleached elements (mg/L) Carbonate 114000 39700 202000 13200 13800 39600 precipitate (mg/kg) Recovery rate 90.6 77.1 110 6.9 51.9 72.7 98.4 59.0 (%) [0072]
(8) Comparison of the scandium (Sc) precipitate recovery rate among different precipitation methods In order to compare the scandium (Sc) precipitate recovery rate among different precipitation methods, a precipitate recovery experiment was conducted using liquid extracts of bioleached scandium (Sc) (4.5 mL each) obtained from scandium (Sc)-containing waste products. Fig. 8 shows the precipitate recovery rates of major elements in the liquid extracts of bioleached scandium (Sc) obtained by the respective precipitation methods.
The scandium (Sc) precipitate recovery rate was approximately 90% for the ammonium bicarbonate method, 60% for the ammonia water method, and 20%
for the oxalic acid method. However, in the case of the ammonium bicarbonate method, the precipitate recovery rates of all other major elements were also 50% or more. Thus, it was impossible to selectively recover scandium (Sc). Meanwhile, in the case of the ammonia water method, the precipitate recovery rates of Al, Ti, and Zr were 50% or more, while the precipitate recovery rates of the other major elements were 50% or less.
This revealed that it is possible to selectively recover a precipitate of scandium (Sc) by the ammonia water method to a greater extent compared with the carbonate precipitation method.
[0073]
(9) Optimization of the scandium (Sc) precipitation method using ammonia water It was thought that a precipitate of scandium (Sc) or the like is obtained in the form of hydroxide by increasing pH according to the precipitation method using ammonia water. Therefore, in order to improve the scandium (Sc) precipitate recovery rate, pH conditions were examined.
As a result, a precipitate of scandium (Sc) in a liquid extract of bioleached scandium (Sc) was successfully recovered at a recovery rate of 100% by adjusting the pH to pH 5 (Fig. 9). In addition to scandium (Sc), precipitates of Al, Ti, and Zr were also recovered at a recovery rate of 100%
while precipitates of the other major elements were recovered at a recovery rate of 50% or less. As a result of elemental analysis, the scandium (Sc) concentration in the liquid extract of bioleached scandium (Sc) was 3.15 mg/L
while the same in the recovered scandium (Sc) precipitate was 327 mg/kg, indicating that scandium (Sc) was concentrated approximately 100-fold.
Based on the above results, dissolved scandium (Sc) as a whole was selectively concentrated and a scandium (Sc) precipitate was successfully recovered by a convenient method of controlling the pH of a liquid extract of bioleached scandium (Sc) using ammonia water.
[0074]
(10) EDX analysis of recovered scandium (Sc) precipitates Scandium (Sc) recovered by the precipitation method using ammonia water was observed in a non-destructive manner by an electron microscope and subjected to EDX elemental analysis.
The precipitate was found to be an aggregate having a several micrometer-size irregular round shape (Fig. 10). In addition, seven elements (A, Ca, Fe, 0, S, Sc, and Ti) showing characteristic distribution were selected from among elements detected by EDX elemental analysis and subjected to mapping. Localization of Sc and Ca was observed at one point of the precipitate. This point was subjected to EDX point analysis. As a result, that the concentrations of these elements at this point were greater than those at the other points (table 6). Meanwhile, Fe, Al, S, Ti, and Zr were found to be dispersed in the precipitate.
[0075]
[Table 6]
Table 6: EDX point analysis of the recovered Sc precipitate (atomic number concentration (%)) (Fig. 10: Points 1, 2, and 3 in the original image) Al Ca Fe Mg S Sc Ti Point 1 13 20 20 3.9 35 0.5 1.1 Point 2 31 0.8 29 3.8 22 0.1 1.9 Point 3 35 0.0 19 1.9 20 0.0 3.7 [0076]
(11) Analysis of rare earth element carbonate recovered from a liquid extract of bioleached rare earth elements using ammonium bicarbonate Table 7 shows analysis results for a liquid extract of bioleached rare earth elements extracted from a rare earth element-containing waste product using the S20 bacterial group and analysis results for a carbonate precipitate (rare earth element concentrate) (123.5 mg) recovered from a liquid extract of bioleached rare earth elements (9 mL). As a result of elemental analysis, the rare earth element concentrations of neodymium (Nd), dysprosium (Dy), and praseodymium (Pr) in the liquid extract were 2,290 mg/L, 500 mg/L, and 430 mg/L, respectively, while the rare earth element concentrations of neodymium (Nd), dysprosium (Dy), and praseodymium (Pr) in the carbonate precipitate (rare earth element concentrate) were 388,000 mg/L, 77,000 mg/L, and 70,000 mg/L, respectively. This indicates that the rare earth elements were concentrated approximately 160-170-fold. The recovery rate of each rare earth element reached 100%. Thus, all rare earth elements were successfully recovered from the liquid extract of rare earth elements. Meanwhile, the amounts of boron (B) and cobalt (Co) contained as impurities were small and the recovery rates thereof were 10% or less. The pH of the liquid extract increased close to pH 6 with the addition of ammonium bicarbonate. It is known that boron (B) and cobalt (Co) do not form a precipitate such as hydroxide at pH 6. Therefore, this could be the reason for the low recovery rates. The above results suggest that the method for recovering a rare earth element concentrate using ammonium bicarbonate is effective means that allows boron (B) and cobalt (Co) to be removed from a liquid extract of rare earth elements so as to exclusively separate and concentrate rare earth elements.
[0077]
[Table 7]
Table 7: Analysis results for the liquid extract of bioleached rare earth elements and the recovered rare earth element carbonate Dysprosium Neodymium Praseodymium Boron Cobalt Iron Dy Nd Pr B Co Fe Liquid extract of bioleached 500 2300 430 140 100 ND
elements (mg/L) Carbonate precipitate 77000 390000 70000 1800 1500 (mg/kg) Recovery 100 110 110 8.7 10.0 rate (%) ND: Not detected (below the detection limit) [0078]
The above results show that a concentrated deposit of rare earth elements was successfully recovered from a liquid extract containing rare earth elements obtained by bioleaching with the use of ammonium bicarbonate or ammonia water in a simple manner. The concentrated deposit of rare earth elements was found to contain rare earth elements obtained from the liquid extract of bioleached elements at a recovery rate of substantially 100%.
[0079]
Example 2:
(A) Experimental Method and Materials (1) Medium and culture conditions Liquid culture was carried out at 30 C under rotary shaking at 120 rpm using minimum inorganic salt medium (BSM) (distilled water; NH4CI: 0.24 g/L; MgSO4-7H20: 0.12 g/L; CaC12.2H20: 0.2 g/L; KH2PO4: 0.05 g/L;
K2HPO4: 0.05 g/L; NaCl: 0.1 g/L; Yeast Extract: 0.1 g/L; Glucose: 2 g/L;
H3B03: 0.6 mg/L; CoC12=6H20: 0.16 mg/L; CuC12: 0.067 mg/L; MnC12: 0.63 mg/L; ZnC12: 0.22 mg/L) subjected to autoclave sterilization (121 C, 15 minutes). The culture pH was adjusted using an HC1 or NaOH solution in accordance with the experiment. Plate culture was carried out with the addition of 20 g/L agar or 20 g/L gellan gum to BSM at 30 C.
[0080]
(2) Environmental samples Soil and water samples were collected from the following 72 sites in total: abandoned mine A (14 sites), abandoned mine B (14 sites), plant waste (24 sites), a waste disposal plant (15 sites), and industrial waste water (5 sites). 0.9% sterilization saline (9 mL) was added to the environmental samples (1 g or 1 mL each), followed by vortex mixing. Thus, suspensions were prepared. Screening samples were obtained from suspensions prepared by adding the environmental samples (1 g or 1 mL each) to 0.9% physiological saline (9 mL) and performing vortex stirring.
[0081]
(3) A dysprosium (Dy) mineralization test BSM medium whose pH was adjusted to pH 2.5 using a potassium hydrogen phthalate-HC1 buffer solution (final concentration: 20 mM) was used. The BSM medium was dispensed into 100-mL Erlenmeyer flasks (50 mL each) and a DyC13 solution was added to result in a dissolved Dy concentration of 100 mg/L. The environmental samples (0.5 mL each) were inoculated into the BSM medium supplemented with Dy, followed by culture for 7 days at 30 C under rotary shaking (120 rpm). BSM medium which was not inoculated with any of the environmental samples and treated under the same conditions was designated as a control. Sampling (1 mL) was conducted according to need. Samples obtained by sampling were centrifuged (15,000 rpm, 5 minutes, 20 C). The supernatants were filtered through a filter (pore size: 0.2 gm, Kurabo Industries Ltd.) to obtain analysis samples. The element concentrations of the samples were determined according to an element concentration analysis method. Dy mineralization capacity of each environmental sample was evaluated by calculating the dissolution percentage based on the dissolved Dy concentration before culture and that of the sample obtained by sampling according to the following Formula (1). Dy concentration analysis was conducted by an elemental analysis method described below.
Formula (1): Dy dissolution percentage on day n of culture (%) = Dyn/Dyo x Dyn: Dissolved Dy concentration on Day n of culture (mg/L) Dyo: Dissolved Dy concentration before culture (mg/L) [0082]
In the case of a test for examining the effects of phosphoric acid addition, a phosphoric acid solution was added to BSM medium to result in a phosphoric acid concentration of 0.7 mM. Culture was carried out using the prepared medium in the manner similar to that in the above Dy mineralization test. BSM medium which was not inoculated with any bacterial strain and treated under the same conditions was designated as a control. Sampling (1 mL each) was carried out at arbitrary time points after the inoculation of the T9 strain. Samples obtained by sampling were subjected to measurement according to the element concentration analysis method.
[0083]
(4) A molecular biological test (a method for determining the 18SrDNA
nucleotide sequence) In order to purify genomic DNA of a separated Dy-metabolizing microorganism, a culture solution obtained by culture for 7 days in BSM
medium (120 rpm, pH 2.5, 30 C) was collected and centrifuged (15,000 rpm, 4 C, 5 minutes) to collect bacterial cells. Then, the bacterial cells were washed twice with physiological saline and thus a genomic DNA extraction sample was obtained. Genomic extraction was carried out using ISOPLANT
(NIPPON GENE CO., LTD.) and sterilized glass beads in combination in accordance with the protocols. PCR
amplification of 18SrDNA was performed using the extracted DNA as a template, a set of primers (NS1 (5'-GTAGTCATATGCTTGTCTC-3') (SEQ ID NO: 1) and NS8 (51-TCCGCAGGTTCACCTACGGA-3') (SEQ ID NO: 2)), and GO Tag Green Master Mix (Promega) under the conditions described below.
[0084]
The PCR reaction was carried out under conditions including:
retention at 95 C for 3 minutes; 30 cycles of degeneration (95 C, 1 minute), annealing (56 C, 1 minute), and elongation (72 C, 1 minute); and retention at 72 C for 5 minutes at the end of the reaction. A clone library was constructed for the amplified DNA using pGEM-T Easy Vector Systems (Promega). Plasmid DNA was purified from recombinant Escherichia coli haying an amplification product according to a common procedure, and the 18SrDNA nucleotide sequence was determined using the recombinant as a template and the following primers. The nucleotide sequence of an insertion fragment was decoded using the following: NS1, NS2 (5'-GGCTGCTGGCACACGACTTGC-3') (SEQ ID NO: 3), NS3 (5'-GCAAGTCTGGTGCCAGCAGCC-3') (SEQ ID NO: 4), NS4 (5'-CTTCCGTCAATTCCTTTAAG-3') (SEQ ID NO: 5), NS5 (5'-AACTTAAAGGAATTGACGGAAG-3') (SEQ ID NO: 6), NS6 (5'-GCATCA-CAGACCTGTTATTGCCTC-3') (SEQ ID NO: 7), NS7 (5LAGGCAATAACAGGTCTGTGATGC-31) (SEQ ID NO: 8), NS8, FM4 (5'-GTTITCCCAGTCACGAC-3') (SEQ ID NO: 9), and RRV
(5!-CAGGAAACAGCTATGAC-31) (SEQ ID NO: 10); and an Applied Biosystems 3730x1 DNA Analyzer (Applied Biosystems).
[0085]
(5) Creation of a phylogenetic tree The determined 18SrDNA nucleotide sequence was subjected to homology search by BLAST (http ://blast.ncbi.nlm.nih.gov/Bla-st.cgi) provided by NCBI and PASTA (http://www.genome.jp/tools/fasta/) provided by UVA. Based on the nucleotide sequence of a strain type showing high homology, a phylogenetic tree was created using CLASTAL W and the phylogenetic tree creation software (Molecular Evolutionary Genetics Analysis (MEG4.0)) by a neighbor-joining method.
[0086]
(6) Growth characteristic test (optimal pH conditions) Hyphal growth was induced in BSM medium at pH 1-9. In the case of pH 1 or 2, 2% (w/v) gellan gum was used for testing. In the other cases, 2%
agar was used for testing. The T9 strain was inoculated at four points on each plate medium. Each plate medium was left at 30 C for 1 week. The growth level was determined by measuring the diameter of each colony. The average value of the diameters of four colonies was calculated.
[0087]
(7) A rare earth element mineralization test A rare earth element metabolism specificity test was conducted using, as test elements other than Dy, cobalt (Co), strontium (Sr), and indium (In) classified as rare metals and scandium (Sc), yttrium (Y), praseodymium (Pr), neodymium (Nd), and europium (Eu) classified as rare earths. BSM medium to which a chloride solution was added to adjust the final concentration of a dissolved element to 100 mg/L was used as a test medium for each element.
Culture was carried out by inoculating 0.5 mL of a T9 strain culture solution (day 4 of preculture) to a test medium at 30 C, 120 rpm, and pH 2.5.
Sampling (1 mL each) was conducted according to need. The concentration of a dissolved sample was determined by an element concentration analysis method described below.
[0088]
(8) Observation of bacterial cells by an electron microscope and EDX
elemental analysis After the Dy mineralization test, a 25% glutaraldehyde solution was added to the T9 strain culture solutions (1 mL each) so as to result in a final concentration of 2%, followed by reaction at 4 C for 1 hour for fixation.
The samples were added dropwise to observation filters (Nano-Percolator, 4KA0122-00, JEOL), suctioned, and washed on the filters twice with 0.9%
physiological saline such that samples for electron microscope observation were prepared. Observation was conducted using a tabletop electron microscope (TM3000: Hitachi High-Technologies Corporation). Elemental analysis was carried out using an energy dispersive X-ray spectrometer (EDX) (Quantax70: Bruker AXS Microanalysis GmbH).
[0089]
(9) A rare earth element mineralization test using a model waste solution A liquid mixture of a 100 mg/L NdC13 solution and a 100 mg/L DyCl3 solution was used as a model waste solution. In addition, shaking culture was carried out at 30 C and 120 rpm. After inoculation of the T9 strain, sampling was conducted according to need. The element concentration of each sample obtained by sampling was determined by an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0090]
(10) Element concentration analysis The element concentration was quantitatively determined by the following method. Each measurement sample stock solution was 1/10-, 1/100-, and 1/1000-diluted with ultrapure water and dissolved elements were quantitatively determined using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.). Standard curves were created using standard solutions (SPEX:
XSTC-622, XSTC-1; Wako Pure Chemical Industries, Ltd.: a sulfuric acid ion standard reagent). The concentration range was determined to be between 0.01 mg/L and 1.0 mg/L. Measurement solutions were prepared by serial dilution in the descending order of the concentration. Each measurement solution was adjusted to have the same liquid properties. Measurement was repeated three times for each sample. The mean value of values with a deviation of 5% or less was designated as a measurement result.
[0091]
(B) Results (1) Screening for a microorganism capable of metabolizing Dy from an environmental sample In order to select a microorganism having Dy mineralization capacity, screening was conducted using, as an index, a decrease in the amount of Dy dissolved in medium.
Fig. 11 shows some of the results of the Dy mineralization test of many environmental samples. On day 7 of culture, some of the environmental samples showed a decrease in the Dy dissolution percentage to approximately 80% or less at two sites (T2, T9) of abandoned mine A. However, reproducible results could not be obtained for samples obtained at the other seventy sites. Therefore, the environmental sample T9 with a significant decrease in the Dy concentration was selected and microorganisms were isolated from the environmental sample.
[0092]
(2) Isolation of Dy-mineralizing microorganisms Microorganisms were isolated using plate medium from samples that were confirmed to constantly carry out mineralization during enrichment culture.
As a result of dilution and inoculation of the culture solution obtained after the Dy mineralization test using the environmental sample T9, a single colony in dark green (in black in Fig. 12) was obtained (Fig. 12). This colony was observed with a magnification of 1000 times by an optical microscope. A microorganism having a bacillary form with a long diameter of approximately 10 im and a short diameter of approximately 2 p.m was observed (Fig. 13). In view of the above, a single cell of the obtained microorganism could be isolated. The microorganism was designated as "the T9 strain.'' [0093]
(3) Growth characteristic BSM plate medium was prepared by variously changing pH to examine the growth of the T9 strain. As a result, favorable growth was observed at pH 2-4 (Fig. 14).
[0094]
(4) Molecular biological test and identification based on systematic taxonomy In order to identify the separated T9 bacterial strain based on taxonomy, 18S rDNA was analyzed. The 18S rDNA nucleotide sequence of the obtained genomie DNA was analyzed, followed by homology search by BLAST and FASTA. As a result, the strain showed high homology to the family Teratosphaeriaceae. In particular, the 18S rDNA sequence was 99.8%
identical to the 18SrDNA sequence of uncultured eukaryote clone RT3n2.
Based on the results, the T9 strain was designated as Teratosphaeriaceae sp.
T9. Fig. 15 shows a phylogenetic tree of Teratosphaeriaceae sp. T9 obtained by the neighbor-joining method.
[0095]
The family Teratosphaeriaceae is classified as a family in the order Capnodiales in the class Dothideonucetes. Many novel species of the family Teratosphaeriaceae have been found from environmental samples after 2000.
Most of bacterial strains classified into the family Teratosphaeriaceae were separated from extremely low moisture environments such as desert, sandstone, and rock. The separation from such low moisture environments is consistent with the fact that the T9 strain was separated from the mine-derived environmental samples. In addition, the T9 strain grows under strongly acidic conditions (pH 2.5). It is also known that some strains of the family Teratosphaeriacea show acidophilic properties (pH 2-5). Meanwhile, there is no report on the involvement of the family Teratosphaeriaceae in metabolism of rare earth elements such as Dy. Thus, the acquisition of Teratosphaeriaceae sp. T9 having Dy-metabolizing capacity is a novel finding.
In the future, it would be possible to determine a specific species of the T9 strain by examining morphological characteristics thereof. As described above, novel Teratosphaeriaceae sp. T9 capable of mineralizing water-soluble rare earth elements in a specific manner was successfully isolated.
[0096]
(5) A Dy mineralization test In order to examine whether or not the isolated T9 strain per se causes changes in dissolution of Dy, a Dy mineralization test was conducted. As a result, dissolved Dy was found to have decreased by approximately 50% on day 3 of culture, the Dy concentration was maintained at the substantially same level until day 7 of culture (Fig. 16). In a system into which the T9 strain had not been inoculated, a decrease in Dy was not observed. Based on the results, it was considered that Dy dissolved in medium becomes insolubilized (mineralization) under certain influence of the T9 strain, which results in a decrease in Dy in a culture solution supernatant.
[0097]
(6) A rare earth element mineralization test In order to examine whether or not the T9 strain mineralizes rare earth elements other than Dy, a mineralization test was conducted using several types of rare earth element solutions.
Fig. 17 shows the results of the mineralization specificity test of the T9 strain on day 3 of culture. Bacterial cell growth was not observed even on day 7 of culture for scandium (Sc) and indium (In) belonging to the rare earth element group among the nine different elements subjected to the test.
This suggested that scandium (Sc) and indium (In) inhibit the growth of the T9 strain. In addition to Dy, a decrease in the concentration of an element dissolved in medium was confirmed for the following four elements classified as rare earth elements: yttrium (Y), praseodymium (Pr), neodymium (Nd), and europium (Eu). A decrease in the dissolution percentage by approximately 50% was confirmed for the five different elements including Dy. However, in the cases of strontium (Sr) and cobalt (Co), a decrease in the dissolution percentage was not confirmed, although bacterial cell growth was confirmed.
Thus, strontium (Sr) and cobalt (Co) are considered to lack metabolizing capacity.
The above results suggested that the T9 strain is capable of mineralizing Y and at least four types of lanthanoids (Pr, Nd, Eu, and Dy) in a specific manner.
[0098]
(7) Electron microscope observation and EDX elemental analysis of bacterial cell surfaces In order to examine what reaction is induced by the T9 strain to reduce Dy dissolved in a culture solution, a culture solution obtained on day 3 of the Dy mineralization test was observed by an electron microscope. Fig. 18 shows an observation image at a magnification of 3,000 times (Fig. 18). As in the case of optical microscopic observation, bacterial cells of the T9 strain in the bacillary form with a long diameter of approximately 10 p.m and a short diameter of approximately 2 i.rm were observed. Some bacterial cells were found to have a sake decanter shape. In addition, a solid having a pomegranate fruit shape, which were not composed of bacterial cells, was observed at a site where an aggregate of bacterial cells was observed.
[0099]
EDX point analysis was conducted on the observation surface (Fig. 18).
Analysis points were the following three points: point A on the solid of the aggregate of bacterial cells, point B on the bacterial cell surface, and a point on the background of a filter surface for fixation. As a result, it was found that Dy was obviously present at point A and point B (table 8). In addition, the Dy concentration at point A where the solid of the aggregate of bacterial cells was analyzed was detected at a level greater than that at point B on the bacterial cell surface. The atomic concentration ratio between Dy and phosphorus was calculated for point A and point B where Dy was present.
The ratio was 1:1 at both points. Then, in order to examine the relationship between Dy and phosphorus, elemental mapping was conducted (fig. 19).
Accordingly, it was found that Dy (blue) was insolubilized, unevenly adhered, and concentrated on the bacterial cell surface of the T9 strain. Further, the concentrated presence of phosphorus (yellow) was also found at the site where Dy was present. However, oxygen (green) was widely distributed regardless of the presence of bacterial cells. Note that Dy (blue), oxygen (green), and phosphorus (yellow) appear in white in Fig. 19.
[0100]
[Table 8]
Table 8: Mass concentrations of elements on the bacterial cell surface of the T9 strain Major element Carbon Oxygen Phosphorus Dysprosium Observation [% (w/w)] [% (w/w)] [% (w/w)] [% (w/w)]
Background 75 21 N.D. 4.1 Point A 41 26 4.6 27 Point B 79 30 3.0 17 [0101]
The above results suggested that the T9 strain causes soluble Dy to be solidified (mineralization) and concentrated on bacterial cells through some kind of metabolism mechanism so as to reduce dissolved Dy, and phosphorus is probably involved in the metabolism.
[0102]
(8) Influence of phosphoric acid on Dy mineralization caused by the T9 strain The results of EDX elemental analysis of the bacterial cell surface suggested that phosphorus is strongly related to Dy enrichment caused by the T9 strain. Therefore, in order to examine the influence of phosphorus, a Dy mineralization test was conducted with the addition of phosphoric acid to ESM medium so as to result in a final concentration of 0.7 mM (Fig. 20). As a result, it was found that the Dy concentration in a medium supernatant decreased by 90% or more within a day during culture with the addition of phosphoric acid. In view of this, it was considered that insolubilization of Dy and phosphorus is not caused by natural adhesion or the like; however, the T9 strain causes Dy mineralization by making use of phosphoric acid.
[0103]
Since it was suggested that phosphoric acid is strongly related to Dy mineralization, a Dy mineralization test was conducted with the addition of phosphoric acid so as to result in different final concentrations of 97 mg/L, 130 mg/Iõ and 200 mg/L. Fig. 21 shows the results obtained on day 1 of culture. The results show that the Dy concentration in a medium supernatant decreased in proportion to the concentration of phosphoric acid added.
Accordingly, it was suggested that Dy mineralization capacity of the T9 strain is improved under the presence of phosphoric acid.
[0104]
(9) A rare earth element mineralization test using a model waste solution Given that an object to be recycled would be related to an Nd magnet, a model Nd magnet solution was prepared by mixing major components thereof and then a mineralization test was conducted. Fig. 22 shows the results of the mineralization test obtained on day 3 of culture. For a liquid mixture containing two elements (Dy and Nd), a decrease in the dissolved concentration of each element was confirmed. The rate of decrease of Dy was about 20%, and that of Nd was about 30%. The amounts of Dy and Nd coexisting in the liquid mixture decreased to substantially constant levels.
Thus, it is not considered that mineralization of either one of the elements would preferentially proceed.
[0105]
Based on the above results, the microorganism T9 strain having Dy-metabolizing capacity and especially mineralization capacity was isolated from the environmental sample of abandoned mine A. The T9 strain was designated as Teratosphaeriacea sp. T9 as a result of molecular biological analysis. The strain was cultured on Dy-containing medium. As a result of electron microscope observation and EDX elemental analysis, it was found that Dy and P were solidified and concentrated at the same sites on bacterial cells. Further, Dy mineralization was improved with the addition of phosphoric acid to the medium. The above results showed that the Dy-mineralizing microorganism T9 strain obtained in this study would be very likely to cause concentration of Dy with high efficiency.
[0106]
In addition, as a result of analysis of Dy mineralization of the T9 strain, it was found that the T9 strain causes the dissolved concentrations of Y and some lanthanoids (Pr, Nd, and Eu) to decrease to approximately 50%. In addition, the decrease rate of dissolved elements in the liquid mixture containing Dy and Nd was approximately 20% to 30%, indicating that both elements are mineralized. The obtained T9 strain was found to be a rare earth element-mineralizing microorganism capable of allowing rare earth elements such as Dy to be concentrated on bacterial cells in a specific manner.
[0107]
Example 3: A leaching experiment with the use of the S20-1 strain (accession no. NITE BP-01592) The following are experiment conditions: TSB (3 g/L): 50 mL; sulfur powder: 0.5 g; initial pH: 3.0 (adjusted with sulfuric acid); rare earth element (REE)-containing waste: 0.5 g; and inoculation of 1% microorganisms Control microorganisms used in the experiment were the S20 bacterial group, Acidithiobacillus ferooxidans ATCC19859, and Acidithiobacillus thiooxidans ATC C19377.
Fig. 23 shows the results. The results shown in fig. 23 revealed that even the S20-1 strain alone can leach elements from waste. Note that the leaching percentage obtained when the S20 bacterial group was used was higher than that obtained when the S20-1 strain alone was used.
[0108]
Example 4: Solidification caused by the T9 strain Since dissolved dysprosium (Dy) was accumulated and solidified on bacterial cells of the 19 strain, dysprosium (Dy) was recovered by collecting bacterial cells. Fig. 24 shows the results of SEM-EDX analysis of the T9 strain. In fig. 24, the upper image is an electron microscopic image (BSE) of the T9 strain obtained after reduction of the dissolved concentration of Dy in medium, the image showing Dy elemental mapping (red) (A). Note that Dy elemental mapping (red) appears in white in the lower image (Dy) (A). Fig.
24 also shows EDX point analysis results obtained at measurement point (i) on the bacterial cell surface and the background point (ii) (B).
As is understood from the results obtained Example 2, when a 100 mg/L dysprosium (Dy) solution was added, it was found that approximately 50% of Dy remained in the supernatant. This means that dysprosium (Dy) in an amount corresponding to 50 mg/L can be recovered in the solid form.
Further, according to the present invention, a method for leaching rare earth elements, comprising treating a material containing rare earth elements with the microorganism or microorganism mixture of the present invention, is provided. The types of rare earth elements to be leached are not particularly limited; however, they are preferably at least one selected from the group consisting of scandium (Sc), praseodymium (Pr), neodymium (Nd), and dysprosium (Dy), and particularly preferably scandium (Sc).
10030]
A method for culturing the microorganism or microorganism mixture of the present invention is not particularly limited as long as rare earth elements can be leached. Thus, favorable culture conditions can be appropriately selected depending on the properties of microorganisms to be used. For example, in the case of the S20 bacterial group used in the Examples, culture can be carried out in medium at pH 2-4 under aerobic conditions of shaking culture or the like at 25 C to 40 C, preferably 25 C to 3.5 C, and particularly preferably 28 C to 32 C.
[0031]
According to the present invention, rare earth elements can be leached by the above method and then the leached rare earth elements can be recovered. The rare earth elements can be recovered by a known method such as centrifugation, filter filtration, or a combination thereof.
[0032]
Preferably, ammonium bicarbonate or ammonia water is added to an extract obtained by treating a rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture of the present invention and the resulting precipitate is recovered. Thus, rare earth elements can be recovered.
[0033]
It is possible to apply the method of the present invention for leaching rare earth elements to ores, electronic devices, urban waste water, and waste water from mines, factories, etc., which contain rare earth elements.
[0034]
[2] A microorganism capable of solidifying rare earth elements a method for solidifying rare earth elements The microorganism of the present invention is a microorganism capable of solidifying rare earth elements.
Specific examples of rare earth elements include the following 17 elements: Sc (scandium), Y (yttrium), La (lanthanum), Ce (cerium), Pr (praseodymium), Nd (neodymium), Pm (promethium), Sm (samarium), Eu (europium), Gd (gadolinium), Tb (terbium), Dy (dysprosium), Ho (holmium), Er (erbium), Tm (thulium), Yb (ytterbium), and Lu (lutetium). The microorganism of the present invention is capable of solidifying at least one of the above rare earth elements. Preferably, the microorganism of the present invention is a microorganism capable of solidifying at least one rare earth element selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
Particularly preferably, the microorganism of the present invention is capable of solidifying all of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
[0035]
According to the present invention, the term solidification means that rare earth elements dissolved in a solution become insoluble (mineralization).
It is possible to confirm by the method described in the Examples below that the microorganism is capable of solidifying rare earth elements. Specifically, a sample containing microoganisms is inoculated into medium for microorganisms to which a chloride solution of a rare earth element (e.g., a DyCl3 solution) has been added, followed by culture under conditions that allow the growth of the microorganism. Thereafter, the capacity to solidify rare earth elements can be evaluated by determining the concentrations of rare earth elements in the supernatant of a sample obtained by sampling. The microorganism capable of solidifying rare earth elements of the present invention can be isolated and collected by screening of wild-type strains, mutant strains, and the like according to the above method or a method based on the method.
[0036]
The genus of the microoganism capable of solidifying rare earth elements of the present invention is not particularly limited. There is a known method for classifying (identifying the species of) a microorganism obtained from an environmental sample or the like based on the information on 16SrRNA, etc. The microorganism used in the present invention may be any microorganism selected from among wild-type strains, mutant strains, and recombinants produced by genetic engineering techniques, etc.
[0037]
Preferable examples of the microoganism capable of solidifying rare earth elements of the present invention include microorganisms belonging to the families Teratosphaeriaceae, Penidiella, Mycosphaerellaceae, or Dothideales. It has been revealed that microoganisms belonging to the families Teratosphaeriaceae, Penidiella, Mycosphaerellaceae, or Dothideales have at least 95% homology in terms of the nucleotide sequences of 18SrDNA, 28SrDNA-D1/D2, and ITS-5.8SrDNA. As described above, according to the present invention, it is possible to use microorganisms having at least 95%
homology to microorganisms belonging to the family Teratosphaeriaceae in terms of the nucleotide sequences of 18SrDNA, 28SrDNA-D1/D2, and ITS-5.8SrDNA. For example, a microoganism belonging to the family Teratosphaeriaceae is the T9 strain (Teratosphaeriaceae sp. T9) isolated in the Examples below. The 19 strain has been deposited with accession no.
NITE BP-01593 in the Patent Microorganisms Depositary, National Institute of Technology and Evaluation (2-5-8 Kazusakamatari, Kisarazu-shi, Chiba 292-0818, Japan) on April 15, 2013. The T9 strain has scientific features of forming black colonies, having a rod-like shape 10 p.m in long diameter and 2 Ilm in short diameter, being in the form of spherical spores 1 vim in diameter, and growing at an optimal pII of 2 to 4.
[0038]
Further, according to the present invention, a method for solidifying rare earth elements, comprising culturing the microoganism capable of solidifying rare earth elements of the present invention in a solution containing rare earth elements, is provided. The types of rare earth elements to be solidified are not particularly limited; however, they are preferably at least one selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy), and particularly preferably dysprosium (Dy).
[0039]
The method for culturing the microorganism of the present invention is not particularly limited as long as rare earth elements can be solidified.
Preferable culture conditions can be selected depending on the properties of microorganisms to be used. For example, in the case of the T9 strain used in the Examples below, culture can be carried out in medium at pH 2-4 under aerobic conditions of shaking culture or the like at 25 C to 40 C, preferably 25 C to 35 C, and particularly preferably 28 C to 32 C.
[0040]
When culturing the microorganism capable of solidifying rare earth elements of the present invention, culture can be preferably carried out under the presence of phosphoric acid. In some cases, it is possible to improve the capacity to solidify rare earth elements of the microoganism under the presence of phosphoric acid.
[00411 According to the present invention, rare earth elements can be solidified by the above method and then the solidified rare earth elements can be recovered. The rare earth elements can be recovered by a known method such as centrifugation, filter filtration, or a combination thereof.
[0042]
It is possible to apply the method of the present invention for solidifying rare earth elements to ores, electronic devices, urban waste water, and waste water from mines, factories, etc., which contain rare earth elements.
[0043]
[3] A method for leaching and solidifying rare earth elements According to the present invention, rare earth elements may be recovered from a rare earth element-containing mineral or rare earth element-containing waste product by culturing the microorganism capable of solidifying rare earth elements of the present invention in a solution containing rare earth elements leached in the step of treating a rare earth element-containing mineral or rare earth element-containing waste product with the microorganism or microorganism mixture capable of leaching rare earth elements of the present invention, thereby solidifying the rare earth elements.
[0044]
The present invention is more specifically described with reference to the Examples below. However, the technical scope of the present invention is not particularly limited to the Examples.
[Examples]
[0045]
Example 1:
(A) Experimental Materials and Method (1) Medium to be used FeSO4 (10 g/L) was added to TSB (Tryptic Soy Broth) (3 g/L) dissolved in ion-exchange water and then 112SO4 was added to adjust the pH to pH 3.0, followed by autoclave sterilization. After sterilization, sulfur (S) (5g/L) was further added. The obtained medium supplemented with sulfur was designated as "TSB+S medium" and used as medium for screening.
[0046]
(2) A method for separating microorganisms for rare earth element leaching TSB+S medium was dispensed into 100-mL Erlenmeyer flasks (50 mL
each) and inoculated with different screening sample suspensions (1 mL each), followed by culture for 7 days under rotary shaking (120 rpm) at 30 C.
Sampling was performed at arbitrary time points for pH measurement.
TSB+S medium which was not inoculated with any of environmental samples and treated under the same conditions was designated as a control. A
decrease in the pH of medium was used as an index of the growth of microorganisms for leaching.
[0047]
(3) A rare earth element bioleaching test using a variety of rare earth element-containing substances TSB+S medium was dispensed into 100-mL Erlenmeyer flasks (50 mL
each) and an arbitrary amount of a rare earth element-containing substance was added to each flask in accordance with the experiment. A day-4 culture solution (0.5 mL) of microorganisms for leaching obtained from each environmental sample was inoculated into the medium, followed by culture under rotary shaking (120 rpm) at 30 C. In addition, the medium which was not inoculated with the bacterial group and treated under the same conditions was designated as a control. Each culture solution was subjected to sampling at arbitrary time points (1 mL each) for the determination of the element concentration.
[0048]
(4) A scale-up test for bioleaching of scandium (Sc) from a scandium (SO-containing mineral using a 5-L tank TSB medium (0.3% (W/V), 3000 mL) was introduced into a 5-L reactor and subjected to autoclave sterilization, followed by aeration stirring at 30 C
pH 3.0, 250 rpm, and 0.33 vvm (1L/min) for 30 minutes. Then, a sulfur powder (30 g) and FeSO4 (30 g) were added. A culture solution of the S20 bacterial group precultured in TSB medium for 4 days (30 mL corresponding to 1% of the total volume) was inoculated into the medium. A scandium (Sc)-containing mineral (30 g) was added to the medium inoculated with the bacterial cells, followed by culture at 30 C, 250 rpm, and 1L/min. The pH in the early stage of culture was adjusted to pH 3Ø Long-term culture was performed, during which TSB medium in an amount equivalent to the amount of evaporated moisture was added every about 30 days. The amount of the evaporated medium was calculated by reading the medium surface position relative to the calibration line on the 5-L tank. Sampling of the measurement sample was performed according to need via a sampling opening. Elemental analysis of the sample was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0049]
(5) A scale-up test for bioleaching of scandium (Sc) from a scandium (Sc)-containing waste product using a 5-L tank TSB medium (0.3% (W/V), 3000 mL) was introduced into a 5-L reactor and subjected to autoclave sterilization, followed by aeration stirring at 30 C
pH 3.0, 250rpm, and 0.33 vvm (1L/min) for 30 minutes. Then, a sulfur powder (30 g) was added. A culture solution of the S20 bacterial group precultured in TSB medium for 4 days (30 mL corresponding to 1% of the total volume) was inoculated into the medium. A scandium (Sc)-containing waste product (300 g) was added to the medium inoculated with the bacterial cells, followed by culture at 30 C, 250 rpm, and 1L/min. The pH in the early stage of culture pH was adjusted to pH 3Ø Sampling of the measurement sample was performed according to need via a sampling opening. Elemental analysis of the sample was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0050]
(6) Investigation of a method for recovering rare earth elements using ammonium bicarbonate 0.5M NH4HCO3 (10% (v/v)) was added to a liquid extract of bioleached rare earth elements, followed by vortex stirring for about 30 seconds. The mixture solution subjected to stirring was centrifuged (20 C, 10,000 prm, 10 minutes) and separated into a supernatant and a precipitate by decantation. 0.5M NH4HCO3 (2 mL) was added to the obtained supernatant and the same operation was repeated. The precipitates obtained by repeating the operation twice were mixed together and dried at 80 C, followed by weight measurement. The resulting dried precipitate was dissolved in aqua regia (1 mL) to obtain an analysis sample. In addition, the supernatant was filtered through a 0.2-lam filter to obtain an analysis sample. Sample analysis was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0051]
(7) Investigation of a method for recovering rare earth elements using oxalic acid A 10% H2C204 solution (0.5 mL) was added to a liquid extract of rare earth elements (4.5 mL) so as to result in a final concentration of 1% (v/v).
Then, an adequate amount of ammonia water was added to adjust the pH to pH
4Ø The resulting solution was vortex stirred for about 30 seconds. The stirred solution was centrifuged (20 C, 10,000 rpm, 10 minutes) and separated into a supernatant and a precipitate by decantation. A 10% H2C204 solution (0.5 mL) was added to the obtained supernatant and the same operation was repeated twice. The precipitates obtained by repeating the recovery operation three times in total were separately dried at 80 C, followed by weight measurement. The resulting dried precipitates were dissolved in aqua regia (1 mL) to obtain analysis samples. In addition, the supernatant was filtered through a 0.2-lam filter to obtain an analysis sample. Sample analysis was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0052]
(8) Investigation of a method for recovering rare earth elements using ammonia water The pH of a liquid extract of rare earth elements (4.5 mL) was adjusted to pH 4.0 or pH 5.0 using ammonia water. The solution was allowed to stand still for about 2 hours at room temperature until a precipitate was formed, followed by centrifugation (10000 rpm, 5 minutes, 20 C). A supernatant and a precipitate were separated using a pipette. The obtained supernatant was filtered through a 0.2-rim filter to obtain an analysis sample. The precipitate was dried (60 C), followed by weight measurement. The dried precipitate was dissolved in ultrapure water or sulfuric acid to obtain an analysis sample.
Sample analysis was carried out using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0053]
(9) A method for analyzing the element concentration The samples obtained by sampling were centrifuged (15,000 rpm, 5 minutes, 20 C) and the supernatants thereof were filtered through disc filters (pore size: 0.2 [tm). The filtrates were designated as measurement sample stock solutions.
Each measurement sample stock solution was 1/10-, 1/100-, and 1/1000-diluted with ultrapure water. Dissolved elements in each solution were quantitatively determined using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.). Standard curves were created using standard solutions (SPEX:
XSTC-622, XSTC-1). The concentration range was determined to be between 0.01 mg/L and 1.0 mg/L. Measurement solutions were prepared by serial dilution in the descending order of the concentration. Each measurement solution was adjusted to have the same liquid properties.
Measurement was repeated three times for each sample. The mean value of values with a deviation of 5% or less was designated as a measurement result.
[0054]
(10) Analysis of recovered precipitates by an energy-dispersive x-ray spectrometer A portion of the precipitate obtained by ammonia precipitation was collected for non-destructive analysis. This analysis sample was fixed on an observation table using carbon tape. Observation and surface analysis were carried out using a tabletop electron microscope (TM3000: Hitachi High-Technologies Corporation) and EDX (Quantax70: Bruker AXS
Microanalysis GmbH) in accordance with the protocols.
[0055]
(B) Results and Discussion =
(1) Separation of microorganisms from environmental samples Representative microorganisms involved in bioleaching have a feature of reducing pH in the growth environment. Thus, at first, it was attempted to separate microorganisms capable of reducing medium pH over the course of growth from environmental samples. As a result, an environmental sample whose pH had declined on day 3 of culture was found. A culture solution of the obtained environmental sample was observed by an optical microscope.
Accordingly, several types of microorganisms having different shapes were observed. Next, in order to reconfirm the presence of the microorganisms in the culture solution of the environmental sample, electron microscope observation was carried out. A bacillus having a long diameter of 1 p.m and a short diameter of 0.5 litm was observed in a part of the sample (fig. 1). No pH decline was confirmed for a culture solution to which no environmental sample had been added. Thus, it is considered that this pH decline was caused by microorganism reaction. Based on the above, the bacterial group in the environmental sample was designated as "the S20 bacterial group."
The S20 bacterial group was sampled in sand near water of Yugama lake in the area of Mount Shirane, Kusatsu, Kusatsu Town, Agatsuma District, Gunma, Japan (North latitude: 36 degrees, 38 minutes, and 38 seconds; East longitude:
138 degrees, 31 minutes, and 40 seconds).
[0056]
The properties of the S20 bacterial group (characteristics, culture conditions, appearance during culture) were described below.
According to molecular biological classification, given that the total bacteria in the bacterial group accounts for 100%, the following microorganisms form flora at the corresponding percentages.
Acidithiobacillus albertesis: 99.72%
Acidithiobacillus thiooxidans: 0.02%
Other microorganisms of the genus Acidithiobacillus: 0.15%
Other microorganisms of the phylum Proteobacteria: 0.02%
No identified microorganisms: 0.09%
In addition, the bacterial group includes Acidomyces acidophilus, Acidomyces acidothermus, and the microorganisms of the genus Acidomyces as eukaryotes.
Sulfur powder is necessary for the growth of the S20 bacterial group.
For example, when the S20 bacterial group is cultured in TSB (Tryptic Soy Broth) medium, which is a naturally occurring medium, the medium color changes from milky white to dark green. Sulfur powder having strong hydrophobicity is dissolved in a culture solution with time during culture.
[0057]
Next, a test of scandium (Sc) bioleaching from oxidized scandium was conducted using the S20 bacterial group (fig. 2). As a result, extraction of approximately 100 mg/L scandium (Sc) from the culture solution of the S20 bacterial group was confirmed on day 15 of culture at an extraction percentage of substantially 100%. Therefore, it was determined to use the S20 bacterial group in subsequent tests.
[0058]
(2) Scandium (Sc) bioleaching from a scandium (Sc)-containing mineral using the S20 bacterial group A test of scandium (Sc) bioleaching from a scandium (Sc)-containing mineral (scandium (Sc) concentration: 400 mg/L: 0.5 g/50 mL medium addition) was conducted using the S20 bacterial group. As a result, the scandium (Sc) extraction percentage was approximately 40% on day 42 of culture (fig. 3). This result suggests that the elements extracted from a scandium (Sc)-containing mineral using the S20 bacterial group can be roughly divided into the following two types based on the tendency to be extracted: elements such as Fe, Mg, and Mn that are likely to be extracted;
and elements such as Al that are unlikely to be extracted. It was considered that scandium (Sc) belongs to the group including Fe, Mg, and Mn and is relatively easily extracted from the sample. However, the scandium (Sc) extraction concentration was 1.5 mg/L, which was the lowest level among the major components (table 1).
[0059]
[Table 1]
Table 1: The element concentrations of the liquid extract of Sc obtained from the Sc-containing mineral using the S20 bacterial group (day 42 of culture) Al Mg Mn Ni Sc Ti Fe S20 (mg/L) 31 15 38 1.1 1.5 6.9 3000 Without bacteria (mg/L) 2.7 9.4 15 0.3 0.3 0.1 1700 [0060]
(3) Scandium (Sc) bioleaching from a scandium (Sc)-containing waste product (titanium (Ti) mineral residue) using the S20 bacterial group A waste sample (scandium (Sc) concentration: 40 mg/L: 10 g/50 mL
medium addition) discharged from an actual plant was subjected to a scandium (Sc) bioleaching test using the S20 bacterial group. As a result, the scandium (Sc) extraction percentage on day 15 of culture was 50%. This was the third highest extraction percentage among elements contained in the waste sample (Fig. 4). The scandium (Sc) extraction concentration was 4 mg/L
which was the lowest level among the major components (table 2). Under the conditions without the presence of the S20 bacterial group, substantially no scandium (Sc) was detected. This suggested that the S20 bacterial group causes scandium (Sc) extraction from the waste product (mineral residue).
The extraction percentage (50% on day 15) of the scandium (Sc)-containing waste product (scandium (Sc) concentration: 40 mg/L) was greater than the extraction percentage (40% on day 42) of the above scandium (Sc)-containing mineral (scandium (Sc) concentration: 400 mg/L). Thus, it is considered that the S20 bacterial group can be used for extraction from low-grade waste.
[0061]
[Table 2]
Table 2: The element concentrations of the liquid extract of Sc obtained from the Sc-containing waste product using the S20 bacterial group (day 7 of culture) Ti Fe Al V Ni Zr Mn Sc S20 (mg/L) 12.0 930 150.0 64.0 540 1.0 69.0 4.0 Without bacteria (mg/L) 0.0 0.0 2.0 0.0 220 0.0 54.0 0.0 [0062]
(4) Bioleaching of rare earth elements from a rare earth element-containing waste product using the S20 bacterial group In order to examine extraction specificity of the S20 bacterial group with respect to other rare earth elements, a waste product containing rare earth elements such as dysprosium (Dy), neodymium (Nd), and praseodymium (Pr) (0.5 g/50 ml, medium addition) was subjected to a rare earth element bioleaching test. As a result, approximately 80% or more of dysprosium (Dy) and approximately 70% or more of praseodymium (Pr) and neodymium (Nd) were extracted by day 7 of culture (fig. 5), while on the other hand, only approximately 10% of iron (Fe) was extracted. No iron (Fe) was extracted from day 0 to day 3. It is considered that rare earth elements can be exclusively and selectively obtained by recovering them in the early stage of culture. As described above, it was revealed that the S20 bacterial group has characteristic ability to extract rare earths ranging from light rare earths such as scandium (Sc) to medium rare earths praseodymium (Pr), neodymium (Nd), and dysprosium (Dy) from a mineral or waste product containing a plurality of rare earth elements.
[0063]
(5) Scaling-up of scandium (Sc) bioleaching from a scandium (Sc)-containing mineral Scandium (Sc) bioleaching from a scandium (Sc)-containing mineral was carried out using a 5-L tank to attempt scaling-up from a flask. The extraction concentration in a flask and that in a 5-L tank were compared on day 42 of culture (table 3). As a result, the scandium (Sc) concentration in the flask was 1.5 mg/L, and that in the 5-L tank was 1.6 mg/L. That is, reproducibility of the scandium (Sc) extraction percentage was obtained in the scale-up test. In addition, the extraction concentrations of Mn, Ni, and Ti in the 5-L tank were about twice those in the flask.
[0064]
[Table 3]
Table 3: Comparison of major element concentrations in the liquid extract of Sc obtained from the Sc-containing mineral for each scale (day 42 of culture) Al Mn Ni Sc Ti 5-L tank mg/L 28 61 2.6 1.6 13 100-mL flask mg/L 31 39 1.1 1.5 6.9 [0065]
The amount of extracted scandium (Sc) increased with time. Thus, in order to further improve scandium (Sc) extraction, long-term culture was conducted (fig. 6). As a result, scandium (Sc) extraction was successfully achieved to a level of 3.5 mg/L at a maximum on day 90 of culture.
Eventually, scandium (Sc) extraction was continued up to day 111 of culture and then the extraction was terminated for convenience of the experiment.
However, even in the case of the control which had not been inoculated with bacteria, scandium (Sc) extraction was achieved to a level of I. mg/L at a maximum. This is probably because a bacterium having extraction capacity of the microorganisms adhering to the waste product had grown as a result of long-term culture.
[0066]
(6) Scandium (Sc) bioleaching from a scandium (Sc)-containing waste product Scandium (Sc) bioleaching from a scandium (Sc)-containing waste product was carried out using a 5-L tank to attempt scaling-up from a flask.
The extraction concentration in the flask and that in the 5-L tank were compared on day 7 of culture (table 4). As a result, the scandium (Sc) concentration in the 5-L tank was 7.5 mg/L which was about twice that in the flask (4.0 mg/L). In addition, the extraction concentrations of Al, Fe, Ti, and Zr in the 5-L tank were about 5 to 10 times those in the flask.
[0067]
[Table 4]
Table 4: Temporal changes in the major element concentrations in the liquid extract of Sc obtained from the Sc-containing waste product for each scale (day 7 of culture) Al Fe Ni Sc Ti Zr 5-L tank mg/L 1400 4400 170 7.5 120 4.9 100-mL flask mg/L 150 930 540 4.0 12 1.0 [0068]
Fig. 7 shows temporal changes in the scandium (Sc) extraction percentage and pH. The results show that the scandium (Sc) extraction percentage was approximately 90% on day 9 of culture. In addition, it was found that pH went up and down from day 2 to day 6 of culture while the scandium (Sc) extraction percentage was significantly improved. This suggests a possibility that scandium (Sc) extraction would not depend on pH
and other factors would be involved in the extraction.
[0069]
In consideration of the above, a tank was designed/constructed for the intended use for scaling-up from culture in a flask to culture in a laboratory-scale reactor. Culture was carried out using the tank. As a result, scandium (Sc) was successfully extracted from both of the scandium (Sc)-containing mineral and waste product samples.
[0070]
(7) Analysis of scandium (Sc) carbonate recovered from a liquid extract of bioleached scandium (Sc) using ammonium bicarbonate Table 5 shows the analysis results for a liquid extract of bioleached scandium (Sc) (bioleached rare earth) extracted from a scandium (Sc)-containing waste product using the S20 bacterial group and the analysis results for a carbonate precipitate (12.4 mg) recovered from a liquid extract of bioleached scandium (Sc) (5 int,). As a result of elemental analysis, it was found that scandium (Sc) concentration in the liquid extract was 0.419 mg/L
while the same in the carbonate precipitate was 166 mg/kg, indicating that scandium (Sc) was concentrated approximately 400-fold. In addition, the recovery rate was 98.4%, indicating that substantially all scandium (Sc) was recovered. Meanwhile, the liquid extract of bioleached rare earth elements also contained elements such as aluminum and iron, showing that elements existing in large amounts were concentrated in carbonate and it was possible to recover at least 90% of the elements. It is considered that ammonium bicarbonate caused an increase in pH of the solution to around neutral pH, which resulted in precipitation of elements other than rare earth elements.
[0071]
[Table 5]
Table 5: Elemental analysis results for the liquid extract of bioleached elements and the recovered carbonate precipitate Aluminum Calcium Iron Magnesium Manganese Nickel Scandium Zinc Al Ca Fe Mg Mn Ni Sc Zn Liquid 312 128 457 475 65.9 135 0.419 23.7 extract of bioleached elements (mg/L) Carbonate 114000 39700 202000 13200 13800 39600 precipitate (mg/kg) Recovery rate 90.6 77.1 110 6.9 51.9 72.7 98.4 59.0 (%) [0072]
(8) Comparison of the scandium (Sc) precipitate recovery rate among different precipitation methods In order to compare the scandium (Sc) precipitate recovery rate among different precipitation methods, a precipitate recovery experiment was conducted using liquid extracts of bioleached scandium (Sc) (4.5 mL each) obtained from scandium (Sc)-containing waste products. Fig. 8 shows the precipitate recovery rates of major elements in the liquid extracts of bioleached scandium (Sc) obtained by the respective precipitation methods.
The scandium (Sc) precipitate recovery rate was approximately 90% for the ammonium bicarbonate method, 60% for the ammonia water method, and 20%
for the oxalic acid method. However, in the case of the ammonium bicarbonate method, the precipitate recovery rates of all other major elements were also 50% or more. Thus, it was impossible to selectively recover scandium (Sc). Meanwhile, in the case of the ammonia water method, the precipitate recovery rates of Al, Ti, and Zr were 50% or more, while the precipitate recovery rates of the other major elements were 50% or less.
This revealed that it is possible to selectively recover a precipitate of scandium (Sc) by the ammonia water method to a greater extent compared with the carbonate precipitation method.
[0073]
(9) Optimization of the scandium (Sc) precipitation method using ammonia water It was thought that a precipitate of scandium (Sc) or the like is obtained in the form of hydroxide by increasing pH according to the precipitation method using ammonia water. Therefore, in order to improve the scandium (Sc) precipitate recovery rate, pH conditions were examined.
As a result, a precipitate of scandium (Sc) in a liquid extract of bioleached scandium (Sc) was successfully recovered at a recovery rate of 100% by adjusting the pH to pH 5 (Fig. 9). In addition to scandium (Sc), precipitates of Al, Ti, and Zr were also recovered at a recovery rate of 100%
while precipitates of the other major elements were recovered at a recovery rate of 50% or less. As a result of elemental analysis, the scandium (Sc) concentration in the liquid extract of bioleached scandium (Sc) was 3.15 mg/L
while the same in the recovered scandium (Sc) precipitate was 327 mg/kg, indicating that scandium (Sc) was concentrated approximately 100-fold.
Based on the above results, dissolved scandium (Sc) as a whole was selectively concentrated and a scandium (Sc) precipitate was successfully recovered by a convenient method of controlling the pH of a liquid extract of bioleached scandium (Sc) using ammonia water.
[0074]
(10) EDX analysis of recovered scandium (Sc) precipitates Scandium (Sc) recovered by the precipitation method using ammonia water was observed in a non-destructive manner by an electron microscope and subjected to EDX elemental analysis.
The precipitate was found to be an aggregate having a several micrometer-size irregular round shape (Fig. 10). In addition, seven elements (A, Ca, Fe, 0, S, Sc, and Ti) showing characteristic distribution were selected from among elements detected by EDX elemental analysis and subjected to mapping. Localization of Sc and Ca was observed at one point of the precipitate. This point was subjected to EDX point analysis. As a result, that the concentrations of these elements at this point were greater than those at the other points (table 6). Meanwhile, Fe, Al, S, Ti, and Zr were found to be dispersed in the precipitate.
[0075]
[Table 6]
Table 6: EDX point analysis of the recovered Sc precipitate (atomic number concentration (%)) (Fig. 10: Points 1, 2, and 3 in the original image) Al Ca Fe Mg S Sc Ti Point 1 13 20 20 3.9 35 0.5 1.1 Point 2 31 0.8 29 3.8 22 0.1 1.9 Point 3 35 0.0 19 1.9 20 0.0 3.7 [0076]
(11) Analysis of rare earth element carbonate recovered from a liquid extract of bioleached rare earth elements using ammonium bicarbonate Table 7 shows analysis results for a liquid extract of bioleached rare earth elements extracted from a rare earth element-containing waste product using the S20 bacterial group and analysis results for a carbonate precipitate (rare earth element concentrate) (123.5 mg) recovered from a liquid extract of bioleached rare earth elements (9 mL). As a result of elemental analysis, the rare earth element concentrations of neodymium (Nd), dysprosium (Dy), and praseodymium (Pr) in the liquid extract were 2,290 mg/L, 500 mg/L, and 430 mg/L, respectively, while the rare earth element concentrations of neodymium (Nd), dysprosium (Dy), and praseodymium (Pr) in the carbonate precipitate (rare earth element concentrate) were 388,000 mg/L, 77,000 mg/L, and 70,000 mg/L, respectively. This indicates that the rare earth elements were concentrated approximately 160-170-fold. The recovery rate of each rare earth element reached 100%. Thus, all rare earth elements were successfully recovered from the liquid extract of rare earth elements. Meanwhile, the amounts of boron (B) and cobalt (Co) contained as impurities were small and the recovery rates thereof were 10% or less. The pH of the liquid extract increased close to pH 6 with the addition of ammonium bicarbonate. It is known that boron (B) and cobalt (Co) do not form a precipitate such as hydroxide at pH 6. Therefore, this could be the reason for the low recovery rates. The above results suggest that the method for recovering a rare earth element concentrate using ammonium bicarbonate is effective means that allows boron (B) and cobalt (Co) to be removed from a liquid extract of rare earth elements so as to exclusively separate and concentrate rare earth elements.
[0077]
[Table 7]
Table 7: Analysis results for the liquid extract of bioleached rare earth elements and the recovered rare earth element carbonate Dysprosium Neodymium Praseodymium Boron Cobalt Iron Dy Nd Pr B Co Fe Liquid extract of bioleached 500 2300 430 140 100 ND
elements (mg/L) Carbonate precipitate 77000 390000 70000 1800 1500 (mg/kg) Recovery 100 110 110 8.7 10.0 rate (%) ND: Not detected (below the detection limit) [0078]
The above results show that a concentrated deposit of rare earth elements was successfully recovered from a liquid extract containing rare earth elements obtained by bioleaching with the use of ammonium bicarbonate or ammonia water in a simple manner. The concentrated deposit of rare earth elements was found to contain rare earth elements obtained from the liquid extract of bioleached elements at a recovery rate of substantially 100%.
[0079]
Example 2:
(A) Experimental Method and Materials (1) Medium and culture conditions Liquid culture was carried out at 30 C under rotary shaking at 120 rpm using minimum inorganic salt medium (BSM) (distilled water; NH4CI: 0.24 g/L; MgSO4-7H20: 0.12 g/L; CaC12.2H20: 0.2 g/L; KH2PO4: 0.05 g/L;
K2HPO4: 0.05 g/L; NaCl: 0.1 g/L; Yeast Extract: 0.1 g/L; Glucose: 2 g/L;
H3B03: 0.6 mg/L; CoC12=6H20: 0.16 mg/L; CuC12: 0.067 mg/L; MnC12: 0.63 mg/L; ZnC12: 0.22 mg/L) subjected to autoclave sterilization (121 C, 15 minutes). The culture pH was adjusted using an HC1 or NaOH solution in accordance with the experiment. Plate culture was carried out with the addition of 20 g/L agar or 20 g/L gellan gum to BSM at 30 C.
[0080]
(2) Environmental samples Soil and water samples were collected from the following 72 sites in total: abandoned mine A (14 sites), abandoned mine B (14 sites), plant waste (24 sites), a waste disposal plant (15 sites), and industrial waste water (5 sites). 0.9% sterilization saline (9 mL) was added to the environmental samples (1 g or 1 mL each), followed by vortex mixing. Thus, suspensions were prepared. Screening samples were obtained from suspensions prepared by adding the environmental samples (1 g or 1 mL each) to 0.9% physiological saline (9 mL) and performing vortex stirring.
[0081]
(3) A dysprosium (Dy) mineralization test BSM medium whose pH was adjusted to pH 2.5 using a potassium hydrogen phthalate-HC1 buffer solution (final concentration: 20 mM) was used. The BSM medium was dispensed into 100-mL Erlenmeyer flasks (50 mL each) and a DyC13 solution was added to result in a dissolved Dy concentration of 100 mg/L. The environmental samples (0.5 mL each) were inoculated into the BSM medium supplemented with Dy, followed by culture for 7 days at 30 C under rotary shaking (120 rpm). BSM medium which was not inoculated with any of the environmental samples and treated under the same conditions was designated as a control. Sampling (1 mL) was conducted according to need. Samples obtained by sampling were centrifuged (15,000 rpm, 5 minutes, 20 C). The supernatants were filtered through a filter (pore size: 0.2 gm, Kurabo Industries Ltd.) to obtain analysis samples. The element concentrations of the samples were determined according to an element concentration analysis method. Dy mineralization capacity of each environmental sample was evaluated by calculating the dissolution percentage based on the dissolved Dy concentration before culture and that of the sample obtained by sampling according to the following Formula (1). Dy concentration analysis was conducted by an elemental analysis method described below.
Formula (1): Dy dissolution percentage on day n of culture (%) = Dyn/Dyo x Dyn: Dissolved Dy concentration on Day n of culture (mg/L) Dyo: Dissolved Dy concentration before culture (mg/L) [0082]
In the case of a test for examining the effects of phosphoric acid addition, a phosphoric acid solution was added to BSM medium to result in a phosphoric acid concentration of 0.7 mM. Culture was carried out using the prepared medium in the manner similar to that in the above Dy mineralization test. BSM medium which was not inoculated with any bacterial strain and treated under the same conditions was designated as a control. Sampling (1 mL each) was carried out at arbitrary time points after the inoculation of the T9 strain. Samples obtained by sampling were subjected to measurement according to the element concentration analysis method.
[0083]
(4) A molecular biological test (a method for determining the 18SrDNA
nucleotide sequence) In order to purify genomic DNA of a separated Dy-metabolizing microorganism, a culture solution obtained by culture for 7 days in BSM
medium (120 rpm, pH 2.5, 30 C) was collected and centrifuged (15,000 rpm, 4 C, 5 minutes) to collect bacterial cells. Then, the bacterial cells were washed twice with physiological saline and thus a genomic DNA extraction sample was obtained. Genomic extraction was carried out using ISOPLANT
(NIPPON GENE CO., LTD.) and sterilized glass beads in combination in accordance with the protocols. PCR
amplification of 18SrDNA was performed using the extracted DNA as a template, a set of primers (NS1 (5'-GTAGTCATATGCTTGTCTC-3') (SEQ ID NO: 1) and NS8 (51-TCCGCAGGTTCACCTACGGA-3') (SEQ ID NO: 2)), and GO Tag Green Master Mix (Promega) under the conditions described below.
[0084]
The PCR reaction was carried out under conditions including:
retention at 95 C for 3 minutes; 30 cycles of degeneration (95 C, 1 minute), annealing (56 C, 1 minute), and elongation (72 C, 1 minute); and retention at 72 C for 5 minutes at the end of the reaction. A clone library was constructed for the amplified DNA using pGEM-T Easy Vector Systems (Promega). Plasmid DNA was purified from recombinant Escherichia coli haying an amplification product according to a common procedure, and the 18SrDNA nucleotide sequence was determined using the recombinant as a template and the following primers. The nucleotide sequence of an insertion fragment was decoded using the following: NS1, NS2 (5'-GGCTGCTGGCACACGACTTGC-3') (SEQ ID NO: 3), NS3 (5'-GCAAGTCTGGTGCCAGCAGCC-3') (SEQ ID NO: 4), NS4 (5'-CTTCCGTCAATTCCTTTAAG-3') (SEQ ID NO: 5), NS5 (5'-AACTTAAAGGAATTGACGGAAG-3') (SEQ ID NO: 6), NS6 (5'-GCATCA-CAGACCTGTTATTGCCTC-3') (SEQ ID NO: 7), NS7 (5LAGGCAATAACAGGTCTGTGATGC-31) (SEQ ID NO: 8), NS8, FM4 (5'-GTTITCCCAGTCACGAC-3') (SEQ ID NO: 9), and RRV
(5!-CAGGAAACAGCTATGAC-31) (SEQ ID NO: 10); and an Applied Biosystems 3730x1 DNA Analyzer (Applied Biosystems).
[0085]
(5) Creation of a phylogenetic tree The determined 18SrDNA nucleotide sequence was subjected to homology search by BLAST (http ://blast.ncbi.nlm.nih.gov/Bla-st.cgi) provided by NCBI and PASTA (http://www.genome.jp/tools/fasta/) provided by UVA. Based on the nucleotide sequence of a strain type showing high homology, a phylogenetic tree was created using CLASTAL W and the phylogenetic tree creation software (Molecular Evolutionary Genetics Analysis (MEG4.0)) by a neighbor-joining method.
[0086]
(6) Growth characteristic test (optimal pH conditions) Hyphal growth was induced in BSM medium at pH 1-9. In the case of pH 1 or 2, 2% (w/v) gellan gum was used for testing. In the other cases, 2%
agar was used for testing. The T9 strain was inoculated at four points on each plate medium. Each plate medium was left at 30 C for 1 week. The growth level was determined by measuring the diameter of each colony. The average value of the diameters of four colonies was calculated.
[0087]
(7) A rare earth element mineralization test A rare earth element metabolism specificity test was conducted using, as test elements other than Dy, cobalt (Co), strontium (Sr), and indium (In) classified as rare metals and scandium (Sc), yttrium (Y), praseodymium (Pr), neodymium (Nd), and europium (Eu) classified as rare earths. BSM medium to which a chloride solution was added to adjust the final concentration of a dissolved element to 100 mg/L was used as a test medium for each element.
Culture was carried out by inoculating 0.5 mL of a T9 strain culture solution (day 4 of preculture) to a test medium at 30 C, 120 rpm, and pH 2.5.
Sampling (1 mL each) was conducted according to need. The concentration of a dissolved sample was determined by an element concentration analysis method described below.
[0088]
(8) Observation of bacterial cells by an electron microscope and EDX
elemental analysis After the Dy mineralization test, a 25% glutaraldehyde solution was added to the T9 strain culture solutions (1 mL each) so as to result in a final concentration of 2%, followed by reaction at 4 C for 1 hour for fixation.
The samples were added dropwise to observation filters (Nano-Percolator, 4KA0122-00, JEOL), suctioned, and washed on the filters twice with 0.9%
physiological saline such that samples for electron microscope observation were prepared. Observation was conducted using a tabletop electron microscope (TM3000: Hitachi High-Technologies Corporation). Elemental analysis was carried out using an energy dispersive X-ray spectrometer (EDX) (Quantax70: Bruker AXS Microanalysis GmbH).
[0089]
(9) A rare earth element mineralization test using a model waste solution A liquid mixture of a 100 mg/L NdC13 solution and a 100 mg/L DyCl3 solution was used as a model waste solution. In addition, shaking culture was carried out at 30 C and 120 rpm. After inoculation of the T9 strain, sampling was conducted according to need. The element concentration of each sample obtained by sampling was determined by an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.).
[0090]
(10) Element concentration analysis The element concentration was quantitatively determined by the following method. Each measurement sample stock solution was 1/10-, 1/100-, and 1/1000-diluted with ultrapure water and dissolved elements were quantitatively determined using an inductively coupled plasma atomic emission spectroscope (ICP-AES) (iCAP6300DUO: Thermo Fisher Scientific K.K.). Standard curves were created using standard solutions (SPEX:
XSTC-622, XSTC-1; Wako Pure Chemical Industries, Ltd.: a sulfuric acid ion standard reagent). The concentration range was determined to be between 0.01 mg/L and 1.0 mg/L. Measurement solutions were prepared by serial dilution in the descending order of the concentration. Each measurement solution was adjusted to have the same liquid properties. Measurement was repeated three times for each sample. The mean value of values with a deviation of 5% or less was designated as a measurement result.
[0091]
(B) Results (1) Screening for a microorganism capable of metabolizing Dy from an environmental sample In order to select a microorganism having Dy mineralization capacity, screening was conducted using, as an index, a decrease in the amount of Dy dissolved in medium.
Fig. 11 shows some of the results of the Dy mineralization test of many environmental samples. On day 7 of culture, some of the environmental samples showed a decrease in the Dy dissolution percentage to approximately 80% or less at two sites (T2, T9) of abandoned mine A. However, reproducible results could not be obtained for samples obtained at the other seventy sites. Therefore, the environmental sample T9 with a significant decrease in the Dy concentration was selected and microorganisms were isolated from the environmental sample.
[0092]
(2) Isolation of Dy-mineralizing microorganisms Microorganisms were isolated using plate medium from samples that were confirmed to constantly carry out mineralization during enrichment culture.
As a result of dilution and inoculation of the culture solution obtained after the Dy mineralization test using the environmental sample T9, a single colony in dark green (in black in Fig. 12) was obtained (Fig. 12). This colony was observed with a magnification of 1000 times by an optical microscope. A microorganism having a bacillary form with a long diameter of approximately 10 im and a short diameter of approximately 2 p.m was observed (Fig. 13). In view of the above, a single cell of the obtained microorganism could be isolated. The microorganism was designated as "the T9 strain.'' [0093]
(3) Growth characteristic BSM plate medium was prepared by variously changing pH to examine the growth of the T9 strain. As a result, favorable growth was observed at pH 2-4 (Fig. 14).
[0094]
(4) Molecular biological test and identification based on systematic taxonomy In order to identify the separated T9 bacterial strain based on taxonomy, 18S rDNA was analyzed. The 18S rDNA nucleotide sequence of the obtained genomie DNA was analyzed, followed by homology search by BLAST and FASTA. As a result, the strain showed high homology to the family Teratosphaeriaceae. In particular, the 18S rDNA sequence was 99.8%
identical to the 18SrDNA sequence of uncultured eukaryote clone RT3n2.
Based on the results, the T9 strain was designated as Teratosphaeriaceae sp.
T9. Fig. 15 shows a phylogenetic tree of Teratosphaeriaceae sp. T9 obtained by the neighbor-joining method.
[0095]
The family Teratosphaeriaceae is classified as a family in the order Capnodiales in the class Dothideonucetes. Many novel species of the family Teratosphaeriaceae have been found from environmental samples after 2000.
Most of bacterial strains classified into the family Teratosphaeriaceae were separated from extremely low moisture environments such as desert, sandstone, and rock. The separation from such low moisture environments is consistent with the fact that the T9 strain was separated from the mine-derived environmental samples. In addition, the T9 strain grows under strongly acidic conditions (pH 2.5). It is also known that some strains of the family Teratosphaeriacea show acidophilic properties (pH 2-5). Meanwhile, there is no report on the involvement of the family Teratosphaeriaceae in metabolism of rare earth elements such as Dy. Thus, the acquisition of Teratosphaeriaceae sp. T9 having Dy-metabolizing capacity is a novel finding.
In the future, it would be possible to determine a specific species of the T9 strain by examining morphological characteristics thereof. As described above, novel Teratosphaeriaceae sp. T9 capable of mineralizing water-soluble rare earth elements in a specific manner was successfully isolated.
[0096]
(5) A Dy mineralization test In order to examine whether or not the isolated T9 strain per se causes changes in dissolution of Dy, a Dy mineralization test was conducted. As a result, dissolved Dy was found to have decreased by approximately 50% on day 3 of culture, the Dy concentration was maintained at the substantially same level until day 7 of culture (Fig. 16). In a system into which the T9 strain had not been inoculated, a decrease in Dy was not observed. Based on the results, it was considered that Dy dissolved in medium becomes insolubilized (mineralization) under certain influence of the T9 strain, which results in a decrease in Dy in a culture solution supernatant.
[0097]
(6) A rare earth element mineralization test In order to examine whether or not the T9 strain mineralizes rare earth elements other than Dy, a mineralization test was conducted using several types of rare earth element solutions.
Fig. 17 shows the results of the mineralization specificity test of the T9 strain on day 3 of culture. Bacterial cell growth was not observed even on day 7 of culture for scandium (Sc) and indium (In) belonging to the rare earth element group among the nine different elements subjected to the test.
This suggested that scandium (Sc) and indium (In) inhibit the growth of the T9 strain. In addition to Dy, a decrease in the concentration of an element dissolved in medium was confirmed for the following four elements classified as rare earth elements: yttrium (Y), praseodymium (Pr), neodymium (Nd), and europium (Eu). A decrease in the dissolution percentage by approximately 50% was confirmed for the five different elements including Dy. However, in the cases of strontium (Sr) and cobalt (Co), a decrease in the dissolution percentage was not confirmed, although bacterial cell growth was confirmed.
Thus, strontium (Sr) and cobalt (Co) are considered to lack metabolizing capacity.
The above results suggested that the T9 strain is capable of mineralizing Y and at least four types of lanthanoids (Pr, Nd, Eu, and Dy) in a specific manner.
[0098]
(7) Electron microscope observation and EDX elemental analysis of bacterial cell surfaces In order to examine what reaction is induced by the T9 strain to reduce Dy dissolved in a culture solution, a culture solution obtained on day 3 of the Dy mineralization test was observed by an electron microscope. Fig. 18 shows an observation image at a magnification of 3,000 times (Fig. 18). As in the case of optical microscopic observation, bacterial cells of the T9 strain in the bacillary form with a long diameter of approximately 10 p.m and a short diameter of approximately 2 i.rm were observed. Some bacterial cells were found to have a sake decanter shape. In addition, a solid having a pomegranate fruit shape, which were not composed of bacterial cells, was observed at a site where an aggregate of bacterial cells was observed.
[0099]
EDX point analysis was conducted on the observation surface (Fig. 18).
Analysis points were the following three points: point A on the solid of the aggregate of bacterial cells, point B on the bacterial cell surface, and a point on the background of a filter surface for fixation. As a result, it was found that Dy was obviously present at point A and point B (table 8). In addition, the Dy concentration at point A where the solid of the aggregate of bacterial cells was analyzed was detected at a level greater than that at point B on the bacterial cell surface. The atomic concentration ratio between Dy and phosphorus was calculated for point A and point B where Dy was present.
The ratio was 1:1 at both points. Then, in order to examine the relationship between Dy and phosphorus, elemental mapping was conducted (fig. 19).
Accordingly, it was found that Dy (blue) was insolubilized, unevenly adhered, and concentrated on the bacterial cell surface of the T9 strain. Further, the concentrated presence of phosphorus (yellow) was also found at the site where Dy was present. However, oxygen (green) was widely distributed regardless of the presence of bacterial cells. Note that Dy (blue), oxygen (green), and phosphorus (yellow) appear in white in Fig. 19.
[0100]
[Table 8]
Table 8: Mass concentrations of elements on the bacterial cell surface of the T9 strain Major element Carbon Oxygen Phosphorus Dysprosium Observation [% (w/w)] [% (w/w)] [% (w/w)] [% (w/w)]
Background 75 21 N.D. 4.1 Point A 41 26 4.6 27 Point B 79 30 3.0 17 [0101]
The above results suggested that the T9 strain causes soluble Dy to be solidified (mineralization) and concentrated on bacterial cells through some kind of metabolism mechanism so as to reduce dissolved Dy, and phosphorus is probably involved in the metabolism.
[0102]
(8) Influence of phosphoric acid on Dy mineralization caused by the T9 strain The results of EDX elemental analysis of the bacterial cell surface suggested that phosphorus is strongly related to Dy enrichment caused by the T9 strain. Therefore, in order to examine the influence of phosphorus, a Dy mineralization test was conducted with the addition of phosphoric acid to ESM medium so as to result in a final concentration of 0.7 mM (Fig. 20). As a result, it was found that the Dy concentration in a medium supernatant decreased by 90% or more within a day during culture with the addition of phosphoric acid. In view of this, it was considered that insolubilization of Dy and phosphorus is not caused by natural adhesion or the like; however, the T9 strain causes Dy mineralization by making use of phosphoric acid.
[0103]
Since it was suggested that phosphoric acid is strongly related to Dy mineralization, a Dy mineralization test was conducted with the addition of phosphoric acid so as to result in different final concentrations of 97 mg/L, 130 mg/Iõ and 200 mg/L. Fig. 21 shows the results obtained on day 1 of culture. The results show that the Dy concentration in a medium supernatant decreased in proportion to the concentration of phosphoric acid added.
Accordingly, it was suggested that Dy mineralization capacity of the T9 strain is improved under the presence of phosphoric acid.
[0104]
(9) A rare earth element mineralization test using a model waste solution Given that an object to be recycled would be related to an Nd magnet, a model Nd magnet solution was prepared by mixing major components thereof and then a mineralization test was conducted. Fig. 22 shows the results of the mineralization test obtained on day 3 of culture. For a liquid mixture containing two elements (Dy and Nd), a decrease in the dissolved concentration of each element was confirmed. The rate of decrease of Dy was about 20%, and that of Nd was about 30%. The amounts of Dy and Nd coexisting in the liquid mixture decreased to substantially constant levels.
Thus, it is not considered that mineralization of either one of the elements would preferentially proceed.
[0105]
Based on the above results, the microorganism T9 strain having Dy-metabolizing capacity and especially mineralization capacity was isolated from the environmental sample of abandoned mine A. The T9 strain was designated as Teratosphaeriacea sp. T9 as a result of molecular biological analysis. The strain was cultured on Dy-containing medium. As a result of electron microscope observation and EDX elemental analysis, it was found that Dy and P were solidified and concentrated at the same sites on bacterial cells. Further, Dy mineralization was improved with the addition of phosphoric acid to the medium. The above results showed that the Dy-mineralizing microorganism T9 strain obtained in this study would be very likely to cause concentration of Dy with high efficiency.
[0106]
In addition, as a result of analysis of Dy mineralization of the T9 strain, it was found that the T9 strain causes the dissolved concentrations of Y and some lanthanoids (Pr, Nd, and Eu) to decrease to approximately 50%. In addition, the decrease rate of dissolved elements in the liquid mixture containing Dy and Nd was approximately 20% to 30%, indicating that both elements are mineralized. The obtained T9 strain was found to be a rare earth element-mineralizing microorganism capable of allowing rare earth elements such as Dy to be concentrated on bacterial cells in a specific manner.
[0107]
Example 3: A leaching experiment with the use of the S20-1 strain (accession no. NITE BP-01592) The following are experiment conditions: TSB (3 g/L): 50 mL; sulfur powder: 0.5 g; initial pH: 3.0 (adjusted with sulfuric acid); rare earth element (REE)-containing waste: 0.5 g; and inoculation of 1% microorganisms Control microorganisms used in the experiment were the S20 bacterial group, Acidithiobacillus ferooxidans ATCC19859, and Acidithiobacillus thiooxidans ATC C19377.
Fig. 23 shows the results. The results shown in fig. 23 revealed that even the S20-1 strain alone can leach elements from waste. Note that the leaching percentage obtained when the S20 bacterial group was used was higher than that obtained when the S20-1 strain alone was used.
[0108]
Example 4: Solidification caused by the T9 strain Since dissolved dysprosium (Dy) was accumulated and solidified on bacterial cells of the 19 strain, dysprosium (Dy) was recovered by collecting bacterial cells. Fig. 24 shows the results of SEM-EDX analysis of the T9 strain. In fig. 24, the upper image is an electron microscopic image (BSE) of the T9 strain obtained after reduction of the dissolved concentration of Dy in medium, the image showing Dy elemental mapping (red) (A). Note that Dy elemental mapping (red) appears in white in the lower image (Dy) (A). Fig.
24 also shows EDX point analysis results obtained at measurement point (i) on the bacterial cell surface and the background point (ii) (B).
As is understood from the results obtained Example 2, when a 100 mg/L dysprosium (Dy) solution was added, it was found that approximately 50% of Dy remained in the supernatant. This means that dysprosium (Dy) in an amount corresponding to 50 mg/L can be recovered in the solid form.
Claims (12)
1. A microorganism, which has accession no. NITE BP-01593.
2. A method for solidifying a rare earth element, comprising the step of culturing the microorganism according to claim 1 in a solution containing rare earth elements.
3. The method according to claim 2, wherein the rare earth element is at least one selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
4. The method according to claim 2 or 3, wherein the rare earth element is dysprosium (Dy).
5. The method according to any one of claims 2 to 4, wherein the microorganism according to any one of claims 1 to 4 is cultured in the solution containing rare earth elements in the presence of phosphoric acid.
6. A method for recovering a rare earth element in a solution, comprising the steps of:
solidifying a rare earth element by culturing the microorganism according to claim 1 in a solution containing rare earth elements; and recovering the rare earth element solidified in the above step.
solidifying a rare earth element by culturing the microorganism according to claim 1 in a solution containing rare earth elements; and recovering the rare earth element solidified in the above step.
7. The method according to claim 6, wherein the rare earth element is at least one selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), and dysprosium (Dy).
8. The method according to claim 6 or 7, wherein the rare earth element is dysprosium (Dy).
9. The method according to any one of claims 6 to 8, wherein the microorganism according to any one of claims 1 to 4 is cultured in the solution containing rare earth elements in the presence of phosphoric acid.
10. A method for recovering a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product, comprising the steps of:
23908544.1 Date Recue/Date Received 2020-09-09 CA 2,911,097 Blakes Ref: 22752/00001 treating the rare earth element-containing mineral or rare earth element-containing waste product with a microorganism or microorganism mixture which is capable of leaching a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product; and solidifying the rare earth element by culturing the microorganism according to claim 1 in a solution containing the rare earth element leached in the above step.
23908544.1 Date Recue/Date Received 2020-09-09 CA 2,911,097 Blakes Ref: 22752/00001 treating the rare earth element-containing mineral or rare earth element-containing waste product with a microorganism or microorganism mixture which is capable of leaching a rare earth element from a rare earth element-containing mineral or rare earth element-containing waste product; and solidifying the rare earth element by culturing the microorganism according to claim 1 in a solution containing the rare earth element leached in the above step.
11. The method according to claim 10, wherein the microorganism according to claim 1 is cultured in the solution containing the rare earth element in the presence of phosphoric acid.
12. The method according to claim 10 or 11, wherein the rare earth element is at least one selected from the group consisting of yttrium (Y), praseodymium (Pr), neodymium (Nd), europium (Eu), dysprosium (Dy), and scandium (Sc).
23908544.1 Date Recue/Date Received 2020-09-09
23908544.1 Date Recue/Date Received 2020-09-09
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