WO2019138307A1

WO2019138307A1 - Extraction of palladium from basalt

Info

Publication number: WO2019138307A1
Application number: PCT/IB2019/050093
Authority: WO
Inventors: Subhash KADAM; Kum. Gayatri Deepaksingh HAZARE
Original assignee: Kadam Subhash
Priority date: 2018-01-09
Filing date: 2019-01-07
Publication date: 2019-07-18

Abstract

The present disclosure relates to a process for the extraction of palladium from basalt. The process of the present disclosure is simple, economical and environment friendly.

Description

EXTRACTION OF PALLADIUM FROM BASALT

FIELD

The present disclosure relates to a process for the extraction of palladium from basalt i.e. siliceous basaltic rock.

DEFINITIONS

As used in the present disclosure, the following words and phrases are generally intended to have the meaning as set forth below, except to the extent that the context in which they are used indicate otherwise.

The expression‘Basalt’ for the purpose of the present disclosure refers to a dark-colored, fine-grained, igneous volcanic rock i.e. siliceous basaltic rock.

The expression‘Mangalwedha region’ for the purpose of the present disclosure refers to the region, which includes the Bhima River flowing through a stretch of 100 km in the Solapur district of Maharashtra, India. The Mangalwedha region particularly refers to the region extending up to 200 km on either side of the Bhima River, represented by the satellitic map which is a straight line and it is geological fault where the rock is deposited.

The expression‘smelting’ for the purpose of the present disclosure refers to a process of melting or fusion, especially to extract a metal from its ore.

The expression‘slag’ for the purpose of the present disclosure refers to a vitreous mass left as a by-product/residue during the smelting of the concentrated fine particles of basalt in the presence of a flux.

The expression‘flux’ for the purpose of the present disclosure refers to a substance which combines with gangue (earthy impurities) present in the roasted or the calcined ore to form a fusible product called slag.

The expression‘gangue’ for the purpose of the present disclosure refers to a commercially undesirable material that surrounds, or is closely mixed with, a desirable mineral in an ore deposit. The expression‘digestion’ for the purpose of the present disclosure refers to stirring a solution maintained at a predetermined temperature.

The expression‘Wilfley table technique’ for the purpose of the present disclosure refers to a simple mechanical panning technique for gravity separation of fine particulate matter.

BACKGROUND

Soil containing basalt may comprise various metals such as Gold (Au), Platinum (Pt), Copper (Cu) and Silver (Ag) and the like. Basalt is a fine-grained, volcanic hard rock, and is a type of igneous rock. When the lava obtained from a volcano, cools quickly, it turns into basalt. Usually, basalt is black or grey.

Platinum (Pt) is a malleable, silvery metal found in trace quantities in the lithosphere and is commonly grouped with five other elements which are referred to as platinum group metals (PGM) or Platinum Group Elements (PGE) i.e. Ruthenium (Ru), Rhodium (Rh), Palladium (Pd), Osmium (Os), and Irridium (Ir). The Platinum Group Metals (PGM) or Platinum Group Elements (PGE) exhibits similar properties. The platinum group metals are often referred to as“noble and precious metals” due to their resistance to oxidation. These metals are also characterized by high melting points, mechanical strength at high temperatures, stable electrical properties, high density, and non-contaminating behavior. Platinum is highly resistant to discoloration and tear and wear properties.

Sometimes extraction of precious metals such as iridium, rhodium, platinum, and palladium is the main focus of a particular industrial operation while in other cases it is a byproduct. Further, the extraction of one of the metals from the platinum group metals is complex due to the presence of other metals. Palladium is useful as specialist metal and is used tremendously in ornament, chemical and atomic industries. It is a strategic metal in the nuclear field. Palladium is useful as a specialist metal and is used tremendously in the chemical industry.

Therefore, the present disclosure envisages an environment friendly process for the extraction of palladium from basalt/ore i.e. siliceous basaltic rock.

OBJECTS

Some of the objects of the present disclosure, which at least one embodiment herein satisfies, are as follows. It is an object of the present disclosure to ameliorate one or more problems of the prior art or to at least provide a useful alternative.

An object of the present disclosure is to provide a simple and economic process for the extraction of palladium.

Another object of the present disclosure is to provide a process for the extraction of palladium that is environment friendly.

Other objects and advantages of the present disclosure will be more apparent from the following description, which is not intended to limit the scope of the present disclosure.

SUMMARY

The present disclosure provides a process for extracting palladium from siliceous basaltic rock. In the process, a predetermined quantity of siliceous basaltic rock material is obtained and ground to obtain fine particles of basalt having a particle size in the range of 100 mesh to 200 mesh. The fine particles of basaltic rock are concentrated to obtain concentrated fine particles. The method step of concentration includes at least one concentration method selected from the group of methods consisting of gravity separation for removing water soluble salts, magnetic separation for removing magnetic impurities and chemical separation for removing Cu and Ag impurities.

The concentrated fine particles of basaltic rock are smelted with a flux for a predetermined time at a predetermined temperature to form a melt comprising slag and mixture of noble metals. The method step of smelting comprises the addition of at least one flux initiator selected from the group consisting of borax, and sodium carbonate. The melt is cooled to a temperature in the range of 20 °C to 30 °C to separate the slag and then the mixture of noble metals associated with iron is extracted in aquaregia at a temperature in the range of 80 °C to 100 °C for a time period in the range of 7 hours to 10 hours to obtain an extract. Aquaregia is a mixture of concentrated nitric acid and concentrated hydrochloric acid optimally in a molar ratio of 1:3. The extract is heated at a temperature in the range of 80 °C to 100 °C until the paste is obtained. The so obtained paste is treated with concentrated sulfuric acid and heated the paste until the white fumes are obtained indicating the evaporation of nitric acid followed by adding hydrochloric acid followed by extraction to obtain a first solution. H₂S gas is passed into the first solution to obtain precipitated sulphides of platinum group metals. The precipitated sulphides of platinum group metals is treated with dilute hydrochloric acid at a temperature in the range of 80 °C to 100 °C to obtain a second solution. The so obtained second solution is treated with paranitrosodiphenylamine/ alpha nitroso beta-naphthol derivatives to obtain a precipitate of palladium. The precipitate of palladium is ignited/heated at a temperature in the range of 200 °C to 300 °C to obtain palladium in the form of palladium oxide (PdO). The so obtained palladium oxide is further heated at a temperature in the range of 800 °C to 900 °C to obtain palladium metal.

DETAILED DESCRIPTION

Basalt is a fine-grained, volcanic hard rock, and is a type of igneous rock. When the lava obtained from a volcano, cools quickly, it turns into basalt. Usually, basalt is black or grey. The chromatic, hard, and siliceous nature of basalt makes the extraction of these noble metals very challenging. The reaction temperature is one of the most important criteria for the separation of noble metals. In due course several efforts have been made to extract precious noble metals from basalt; however, no significant results have been obtained.

Therefore, the present disclosure provides a simple and economic process for the extraction of palladium from basalt. The process for the extraction of palladium from basalt includes a series of steps comprising collecting a basalt sample, concentrating the sample to remove the undesired impurities present therein, and subjecting the concentrated sample to at least one extraction method to extract palladium oxide.

In the first step of the process of the present disclosure, a basalt sample is collected and ground to obtain fine particles of basalt. The grinding of the basalt is typically carried out to obtain fine particles of basalt having a particle size in the range of 100 mesh to 200 mesh. The grinding of basalt can be carried out by using conventional methods/techniques, selected from the group consisting of ball milling, autogenous milling, semiautogenous milling, and the like. In accordance with one of the embodiments of the present disclosure, the grinding of the basalt is carried out by the ball mill method.

In the second step, the fine particles of basalt are subjected to a concentration process to remove the undesired species present therein. The concentration of minerals/ores can be carried out by any of the well-known techniques known in the art. The concentration of the fine particles of basalt in accordance with the present disclosure can be carried out by using at least one method selected from the group of methods consisting of separation under gravity, magnetic separation, chemical separation and the like.

In one embodiment of the present disclosure, the concentration of the fine particles of basalt is carried out by a multistep process in which the fine particles of basalt are first treated with a magnetic separator to remove iron impurities. The iron free fine particles of basalt thus obtained, are then purified by using Wilfley table technique to remove the lighter particles present therein. The Wilfley table technique is a well-known technique in which separation is based on shape and density of the fine particulate matter. Further, the fine particles of basalt, free from iron impurities and free from lighter particles, are treated with dilute nitric acid. The copper (Cu) and silver (Ag) impurities, if present in basalt get dissolved in dilute nitric acid. The concentrated fine particles of basalt thus obtained is significantly free from iron, silver, copper, and light particles.

In the third step of the process of the present disclosure, the so obtained concentrated fine particles of basalt are smelted with a flux at a predetermined temperature for a predetermined time to obtain a melt comprising slag and a mixture of noble and precious metals.

The choice and selection of the flux used for the purpose of the present disclosure depend on the type of gangue materials present in the concentrated fine particles of basalt. During smelting, the undesired materials (conventionally known as gangue) present in the concentrated fine particles of basalt, react with the flux to form slag. The flux material used in the process of the present disclosure can be selected from the group consisting of borax (Na₂B₄0₇), sodium carbonate (Na₂C0₃), potassium nitrate (KN0₃) and ammonium nitrate (NH₄N0₃). In an exemplary embodiment, borax is used as flux material.

In an exemplary embodiment of the present disclosure, the concentrated fine particles of basalt is mixed with borax, sodium carbonate (Na₂C0₃), starch (maize grains) and silver to obtain a mixture. All the components are typically mixed in a pre-determined weight proportion. Borax, sodium carbonate, starch (maize grain) and silver can be typically added in amounts varying from 15 wt% to 25 wt%; 15 wt% to 25 wt%; 1 wt% to 2 wt%; and 10 wt% to 12 wt%, respectively, based on per kg weight of the concentrated fine particles of basalt. The obtained mixture is then charged in a crucible and placed in a Blast-Furnace. The Blast furnace is then heated at a temperature of 1000 °C. The temperature of the Blast-furnace can be maintained at about 1000 °C by using coke as a fuel. At this temperature of about 1000 °C, the concentrated fine particles of basalt react with the flux; since the reaction is highly exothermic, the crucible placed inside the Blast-furnace reaches a high temperature of about 1800 °C. At this high temperature, the concentrated fine particles of basalt and the flux melt together and form a melt. The melt, thus formed comprises slag and a mixture of noble metals.

In the fourth step of the process of the present disclosure, the melt is cooled down to a temperature ranging from 20 °C to 30 °C. After cooling the melt to room temperature, the slag adheres on to the walls of the furnace, which can be removed and the mixture of noble metals are separated. The term‘slag’ in the context of the present disclosure refers to a vitreous mass left as a by-product/residue during smelting of the concentrated fine particles of basalt in the presence of the flux.

The separation of slag can be accomplished by using any conventional methods known in the related prior-art. The slag in accordance with the process of the present disclosure can be separated by mechanical means, for example, by crushing the slag. The slag so obtained can be used for road construction and in the preparation of bricks.

In the fifth step, the cooled mixture of noble metals is treated with a mixture of concentrated nitric acid and concentrated hydrochloric acid at a temperature in the range of 80 °C to 90 °C to obtain a first solution. The noble metals have a strong affinity towards these mineral acids. The ratio of the amount of concentrated nitric acid to concentrated hydrochloric acid used in the process of the present disclosure ranges from 1:1/2 to 2:1

In the sixth step, the so obtained first solution containing noble metals is treated with concentrated sulfuric acid followed by treatment with dilute hydrochloric acid to obtain a second solution. The treatment of the first solution with concentrated sulfuric acid followed by treatment with dilute hydrochloric acid is carried out for removal of the nitric acid fumes present in the first solution.

In the seventh step, the second solution is subjected to digestion by maintaining the temperature in the range of 85 °C to 90 °C for a time period ranging from 3 hours to 8 hours to obtain a residue. Digestion refers to stirring a solution maintained at a predetermined temperature. After the digestion, the so obtained residue can be filtered through a funnel to obtain a solid and a filtrate.

In the eighth step, hydrogen sulfide (H₂S) is passed in the filtrate to obtain precipitated sulphides of platinum group metals. The amount of H₂S gas passed in the filtrate is dependent on the concentration of the filtrate. In an exemplary embodiment, the H₂S gas is passed till complete precipitation of sulphide salt is observed.

The precipitated sulphides of platinum group metals is treated with cone hydrochloric acid at a temperature in the range of 80 °C to 100 °C to obtain a third solution and then extracted with diluted hydrochloric acid.

The so obtained third solution is treated with para-nitrosodiphenylamine /alpha nitroso beta phenol and derivatives thereof, at a room temperature in the range of 25 °C to 50 °C for a time period in the range of 1 hour to 5 hours to obtain precipitate of palladium. The so obtained precipitate of palladium is typically red or rosy red in color. The precipitate of palladium is heated at a temperature in the range of 200 °C to 300 °C to obtain palladium in the form of palladium oxide (PdO) and on further heating at a temperature in the range of 800 °C to 900 °C to obtain palladium metal with silvery white color.

The present disclosure is further illustrated herein below with the help of the following experiments. The experiments used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of embodiments herein. These laboratory scale experiments can be scaled up to an industrial/commercial scale.

Experimental Details:

Experiment-1: Extraction of palladium from basalt of Mangalwedha:

5 kg basalt was collected from Mangalwedha (Maharashtra, India) and subjected to a grinding process to obtain fine particles of 100 mesh size. The fine particles were treated with a magnetic separator followed by Wilfley table technique. Afterwards, the fine particles of basalt were treated with 1 liter of dilute nitric acid. The concentrated fine particles of basalt (1 kg), thus, obtained were mixed borax (0.25 kg), sodium carbonate (0.25 kg), starch (0.02 kg) and silver (0.001 kg), and were charged in a pre-heated crucible placed in a Blast- Furnace, at a temperature of 1000 °C. Due to the exothermic nature of the reaction, the temperature of the crucible placed inside the Blast-Furnace reaches to about 1800 °C. At this high temperature of about 1800 °C, the concentrated fine particulate matter of basalt melts completely and forms a melt comprising a mixture of noble metals along with iron and slag. The melt, thus obtained was cooled down to room temperature. The slag was then separated from the mixture of noble metals by mechanical means.

The mixture of the noble metals, thus obtained (lkg) was treated with 1 liter of dilute nitric acid and 500 ml of hydrochloric acid at 70 °C to obtain a paste. The paste containing noble metals was then subjected to digestion by maintaining the paste at 80 °C for 8 hours to obtain a residue (800 gms).

The residue was filtered through a funnel to obtain a filtrate (500 ml) and a solid (700 gms).

H₂S gas was passed through the filtrate to obtain precipitated sulphides of platinum group metals.

The precipitated sulphide of noble metals was treated with cone hydrochloric acid (300 ml) at 80 °C to obtain a second solution.

The so obtained second solution was treated with para-Nitrosodiphenylamine/alpha nitroso beta naphthol (2 gm) to obtain rosy red colored precipitates of palladium.

The precipitate of palladium (5 gm) which is in the form of metallic bead was heated at 250 °C to obtain a black metallic oxide of palladium in the form of palladium oxide (PdO) (10 mg).

On further heating/ignition of palladium oxide at 800 °C, palladium oxide converts into metallic palladium having silvery white color.

TECHNICAL ADVANCES AND ECONOMICAL SIGNIFICANCE

The present disclosure described herein above has several technical advantages including, but not limited to, the realization of the process of extraction of palladium from basalt: that is a simple and environment friendly process; and

- slag obtained in the process of the present disclosure can be used in road construction, thereby making the process economical and environment friendly.

Throughout this specification the word“comprise”, or variations such as“comprises” or “comprising”, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The use of the expression“at least” or“at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Any discussion of documents, acts, materials, devices, articles or the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

The numerical values mentioned for the various physical parameters, dimensions or quantities are only approximations and it is envisaged that the values higher/lower than the numerical values assigned to the parameters, dimensions or quantities fall within the scope of the disclosure, unless there is a statement in the specification specific to the contrary.

While considerable emphasis has been placed herein on the components and component parts of the preferred embodiments, it will be appreciated that many embodiments can be made and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other changes in the preferred embodiment as well as other embodiments of the disclosure will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

Claims:

1. A process for extracting palladium from siliceous basaltic rock, said process comprising:

a. obtaining a predetermined quantity of basalt material and grinding it to obtain fine particles of siliceous basaltic rock having a particle size in the range of 100 mesh to 200 mesh;

b. concentrating said fine particles of siliceous basaltic rock to obtain concentrated fine particles of siliceous basaltic rock;

c. smelting said concentrated fine particles of siliceous basaltic rock t with a flux for a predetermined time period and at a predetermined temperature to form a melt comprising slag and a mixture of noble metals;

d. cooling said melt to a temperature in the range of 20 °C to 30 °C to obtain a cooled mixture of noble metals;

e. dissolving said cooled mixture of noble metals into a mixture of concentrated nitric acid and concentrated hydrochloric acid at a temperature in the range of 60 °C to 80 °C to obtain a paste wherein the ratio of concentrated nitric acid to concentrated hydrochloric acid in said mixture is in the range of 1:1/2 to 2:1; f. treating said paste with concentrated sulfuric acid followed by treating it with dilute hydrochloric acid to obtain a first solution;

g. digesting said first solution by maintaining the temperature at 80 °C for a time period ranging from 3 hours to 8 hours to obtain a residue; h. filtering said residue to obtain a solid and a filtrate;

i. passing H₂S gas into said filtrate to obtain precipitated sulphides of platinum group metals;

j. treating said precipitated sulphides of platinum group metals with cone hydrochloric acid at a temperature in the range of 80 °C to 100 °C to obtain a second solution;

k. treating said second solution with paranitrosodiphenylamine/ alpha nitroso beta naphthol at a temperature in the range of 200 °C to 250 °C for a time period in the range of 1 hour to 4 hours to obtain a precipitate of palladium; l. heating said precipitate of palladium at a temperature in the range of 200 °C to 250 °C to obtain palladium in the form of palladium oxide (Pd0₃); m. igniting said palladium trioxide at a temperature in the range of 750 °C to 1000 °C to obtain palladium metal.

2. The process as claimed in claim 1, wherein the process step of concentration includes at least one concentration method selected from the group of methods consisting of gravity separation, magnetic separation and chemical separation.

3. The process as claimed in claim 1, wherein the process step of concentrating the fine particles of siliceous basaltic rock comprises the following steps:

i. subjecting said fine particles of siliceous basaltic rock to magnetic separation to remove magnetic impurities present therein;

ii. subjecting said magnetic impurity free fine particles of siliceous basaltic rock obtained from step (i) to a separation under gravity using Wilfley table technique to remove the lighter particles present therein; and

iii. treating said fine particles of siliceous basaltic rock obtained in method step (ii) with dilute nitric acid to remove Cu and Ag impurities.

4. The process as claimed in claim 1, wherein said siliceous basaltic rock is sourced from Mangalwedha region.

5. The process as claimed in claim 1, wherein the flux includes borax, in an amount in the range of 15 wt% to 25 wt%, based on the total weight of the concentrated fine particles of basalt.

6. The process as claimed in claim 1, wherein the method step of smelting said concentrated fine particles of siliceous basaltic rock comprises the addition of at least one flux initiator selected from the group consisting of starch, sodium carbonate and silver.

7. The process as claimed in claim 6, wherein said flux initiator is a mixture of sodium carbonate, starch, and optionally silver in amounts varying from 15 wt% to 25 wt%; 1 wt% to 2 wt%; and 10 wt% to 12 wt%, respectively, based on the total weight of the concentrated fine particles of siliceous basaltic rock.

8. The process as claimed in claim 1, wherein said smelting of said concentrated fine particles of basalt is carried out at a temperature is in the range of 1000 °C to 1800 °C for a time period in the range of 1.5 hours to 2 hours and said ignition of said sulfates of noble metals is carried out at a temperature in the range of 1000 °C to 1500 °C for a time period in the range of 1.5 hours to 2 hours.