CN110745855A

CN110745855A - Preparation method of high-purity cerium hydroxide

Info

Publication number: CN110745855A
Application number: CN201810724656.6A
Authority: CN
Inventors: 肖兴才
Original assignee: LESHAN DONGCHEN ADVANCED MATERIAL Co Ltd
Current assignee: LESHAN DONGCHEN ADVANCED MATERIAL Co Ltd
Priority date: 2018-07-04
Filing date: 2018-07-04
Publication date: 2020-02-04

Abstract

The invention belongs to the field of hydrometallurgy of rare earth production, and relates to a preparation method of high-purity cerium hydroxide, which comprises the steps of dissolving high-purity cerium carbonate by nitric acid to prepare a cerium nitrate solution with a certain concentration, filtering by a filter tank, removing oil by ultrasonic waves, heating, concentrating and crystallizing to prepare a cerium nitrate crystal for later use, slowly adding hydrogen peroxide and a small amount of ammonia water into cerium nitrate filtrate to oxidize Ce (NO3)3 into Ce (OH)3 O.OH, controlling the temperature of a reaction system to be below 35 ℃, controlling the oxidation time to be 30-60 min, maintaining the pH value of a solution system to be 5-6, stirring the solution, adding ammonia water to maintain the pH value of the solution to be 6-7, fully oxidizing Ce (NO3)3 into Ce (OH)3 O.OH, finally heating the solution to 90-100 ℃ after a small amount of ammonia water, preserving heat for 10-30 min, maintaining the pH value of the solution to be 8-9, the Ce (OH)3O & OH is completely converted into Ce (OH)4, heavy metal precipitation is reduced, and redundant hydrogen peroxide is removed, so that the problem of low product purity of the cerium hydroxide prepared by the existing cerium hydroxide preparation method is solved.

Description

Preparation method of high-purity cerium hydroxide

Technical Field

The invention belongs to the field of hydrometallurgy of rare earth production, and relates to a preparation method of high-purity cerium hydroxide.

Background

The reserve of rare earth in China is the front of the world, wherein cerium accounts for about 50 percent of the total amount of rare earth. Cerium hydroxide is the most productive tetravalent cerium product. The cerium hydroxide is non-toxic, the high-purity cerium hydroxide is an important industrial raw material, and can be used as a fluorescent screen additive of a color television to change the toughness, strength and other optical properties of fluorescent glass, and the market demand is large. The cerium hydroxide can also be used as an automobile exhaust purification catalyst and can replace part of noble metals. The cerium hydroxide can also be used for a glass decoloration clarifier, a reagent for preparing ceric ammonium nitrate, ceric sulfate, ceric ammonium sulfate and the like. With the further development of the rare earth industry, higher requirements are put forward on the purity and various performances of cerium hydroxide products.

There are many methods for producing cerium hydroxide, and at present, there are four main methods: (1) chinese patent document CN87100620A proposes a method for producing cerium hydroxide by dividing an acidic aqueous solution containing cerium and a rare earth element other than cerium into two parts, adding an alkali metal hydroxide or ammonia to the first part, separating the resulting rare earth hydroxide solid, and adding the solid along with an oxidizing agent to the second part to produce a cerium hydroxide solid. The method has the advantages of short process flow, less introduced impurities, but low purity of the obtained product, wherein cerium oxide only accounts for 83.6 percent of the total rare earth content. (2) The method for producing cerium hydroxide proposed by chinese patent document CN 1075171a is to add a precipitant into a mixed rare earth feed liquid to generate rare earth carbonate, and then add an oxidant to generate a ceric double salt and cerium peroxide, during which hydrogen ions generated by hydrolysis can dissolve non-cerium rare earth carbonate, and the ceric sulfate is generated and is subjected to complete heating reaction to prepare cerium hydroxide. The method has simple process, less introduced impurity ions, but the oxidant is directly added into the rare earth carbonate, the oxidation speed is slow, the speed of dissolving the trivalent rare earth by the hydrogen ions generated by hydrolysis is limited, the trivalent rare earth can be removed only by strictly controlling conditions, and the purity of the cerium hydroxide can be improved. (3) The method for producing cerium hydroxide proposed by Chinese patent document CN 1269327A takes mixed rare earth feed liquid as raw material, and alkali-converts RE 3-precipitate into RE (OH) 3; adding an oxidant to oxidize Ce (OH)3 in the mixed rare earth hydroxide into Ce (OH) 4; adding acid to dissolve the rare earth precipitate completely, wherein the cerium contained in the solution coexists with other trivalent rare earth in a four-valence state form, and then adding a precipitant or heating the solution to destroy the stability of cerium (IV) in the acidic solution so as to separate out the cerium (IV) in a form of cerium hydroxide particles, thereby obtaining a suspension containing cerium hydroxide; filtering and separating to obtain filtrate, namely the cerium-less lanthanum-rich rare earth chloride solution, and washing the filter cake to obtain the cerium hydroxide. However, the cerium hydroxide produced by the method is low in purity, carries a large amount of rare earth impurities, is difficult to wash and causes resource waste, and the separation of the cerium hydroxide is controlled by controlling the pH of the solution to be 1-2, needs weak alkali to control the pH of the solution, and is difficult to control in actual operation. (4) The method for producing cerium hydroxide proposed by chinese patent document CN 1048239a is to produce cerium hydroxide by using potassium permanganate in an acidic aqueous solution containing cerium and rare earths other than cerium. The process comprises the steps of oxidizing trivalent cerium into tetravalent cerium by potassium permanganate to generate hydrated cerium hydroxide and manganese (IV) hydroxide precipitate, separating cerium from other non-cerium rare earths, adding sulfite into the precipitate to reduce the tetravalent cerium and the tetravalent manganese into Ce2(SO4)3 and divalent manganese, adding alkali metal salt to generate sodium cerium (III) sulfate double salt precipitate to separate cerium and manganese, and finally converting the double salt alkali into cerium hydroxide. The cerium hydroxide produced by the method is easy to filter, has high oxidation rate and high reaction speed, but still has the following serious defects: the process is complicated and the flow is too long; the used raw materials and auxiliary materials are more, and more non-rare earth impurities are introduced, so that the purity of cerium hydroxide is lower; the solid-liquid separation is carried out for many times, the washing times are many, and the yield is reduced.

The preparation methods of the cerium hydroxide all start from mixed rare earth feed liquid, the obtained cerium hydroxide product is difficult to filter and has low purity, and Na +, Mn2+, SO 42-and other rare earth impurities and the like are wrapped in the cerium hydroxide product, SO that the purity of the cerium hydroxide obtained by the methods is low, and the cerium hydroxide is limited in application in a plurality of fields with high requirements on product impurities, such as manufacturing automobile exhaust purifiers, producing ammonium cerium nitrate and the like.

Disclosure of Invention

In view of the above, the invention provides a preparation method of high-purity cerium hydroxide to solve the problem of low product purity of cerium hydroxide prepared by the existing preparation method of cerium hydroxide.

In order to achieve the above object, the present invention provides a method for preparing high purity cerium hydroxide, comprising the steps of:

A. quantitatively putting cerium carbonate with the purity of more than 99.99% into a reaction kettle, adding nitric acid for dissolving and heating to obtain a cerium nitrate solution with the acidity of 0.8-1 mol/L;

B. putting the cerium nitrate solution into a primary closed filter tank, filtering the cerium nitrate solution by using a plate frame, putting the filtered cerium nitrate solution into a secondary closed filter tank, filtering the cerium nitrate solution again, and removing oil from the cerium nitrate solution after the plate frame is filtered by using ultrasonic waves;

C. heating and concentrating the deoiled cerium nitrate solution, and then placing the solution in a crystallization tray for natural crystallization to prepare cerium nitrate crystals for later use;

D. dissolving a cerium nitrate crystal by using desalted water, and filtering the dissolved cerium nitrate solution through a microfilter with a certain pore diameter, wherein the mass concentration of the cerium nitrate solution is 100-120 g/L;

E. slowly adding hydrogen peroxide and a small amount of ammonia water into the cerium nitrate filtrate to oxidize Ce (NO3)3 into Ce (OH)3 O.OH, controlling the temperature of a reaction system to be below 35 ℃, controlling the oxidation time to be 30-60 min, maintaining the pH value of a solution system to be 5-6, stirring the solution, adding ammonia water to maintain the pH value of the solution to be 6-7, fully oxidizing Ce (NO3)3 into Ce (OH)3 O.OH, finally adding a small amount of ammonia water, heating the solution to 90-100 ℃, preserving the temperature for 10-30 min, maintaining the pH value of the solution to be 8-9, completely converting Ce (OH)3 O.OH into Ce (OH)4, reducing heavy metal precipitates, and removing redundant hydrogen peroxide;

F. the Ce (OH)4 precipitate is put into a filter tank to be washed for a plurality of times, and the washed Ce (OH)4 precipitate is filtered and pumped to dryness by a plate frame under certain pressure to prepare a filter cake;

G. and transferring the filter cake into an oven, and drying in a constant-temperature flash evaporation dryer at 90-95 ℃ for 20-24 hours to obtain a high-purity cerium hydroxide product.

Further, the molar ratio of Ce3+ to NO 3-in cerium carbonate and nitric acid in step A was 1: 3.

And further, double-layer filter cloth is arranged in the first-stage closed filter tank and the second-stage closed filter tank in the step B, and filter paper is padded between the double-layer filter cloth.

Furthermore, the mesh number of the double-layer filter cloth in the step B is 200-300 meshes.

Furthermore, the molar ratio of the added amount of the hydrogen peroxide to the added amount of the cerium nitrate in the step E is (2-4): 1, and the mass ratio of the total amount of the hydrogen peroxide to the total amount of the ammonia water is (1.20-1.25): 1.

And further, the ammonia water in the step E is cold ammonia water with the temperature of 10-15 ℃.

And further, in the step E, in the process of slowly adding the cerium nitrate filtrate into hydrogen peroxide, introducing oxygen or ozone as an auxiliary oxidant.

And further, adding hydrogen peroxide into the cerium nitrate filtrate while stirring in the step E.

Further, step F, the Ce (OH)4 precipitate is put into a filter tank to be washed once by water and then washed once by absolute ethyl alcohol.

And G, further packaging the high-purity cerium hydroxide product dried in the step G by adopting two layers of plastic inner films.

The invention has the beneficial effects that:

1. the preparation method of the high-purity cerium hydroxide disclosed by the invention is characterized in that high-purity cerium carbonate is dissolved by nitric acid to prepare a cerium nitrate solution with a certain concentration, the cerium nitrate solution is filtered by a filter tank and then degreased by ultrasonic waves, and then the cerium nitrate crystal is prepared by heating, concentrating and crystallizing for later use. In the process of preparing cerium hydroxide by using the dissolved cerium nitrate, ammonia water is added into a cerium nitrate solution for three times, a small amount of ammonia water and hydrogen peroxide are slowly added into a cerium nitrate filtrate, the reaction of the hydrogen peroxide and the cerium nitrate is a heat release process, the temperature of a reaction system is gradually increased in the reaction process, the generated cerium peroxide is decomposed into cerium hydroxide, the cerium hydroxide is continuously combined with the hydrogen peroxide to generate cerium peroxide, the hydrogen peroxide is insufficient in an oxidation reaction process, the oxidation rate is reduced, the hydrogen peroxide consumption is high, the PH value of the solution system is controlled to be 5-6, the primary supply of the ammonia water is reduced, the reaction temperature is controlled to be below 35 ℃, the whole oxidation process can be gradually oxidized in stages, and the oxidation efficiency of the cerium nitrate is improved. Secondly, ammonia water is provided again after most of cerium nitrate is oxidized, and the PH of the solution is maintained at 6-7, so that Ce (NO3)3 is fully oxidized into Ce (OH)3 O.OH, under a reaction system with the PH of 6-7, the oxidation rate of the cerium nitrate reaches 98%, and the oxidation is basically completed completely. And finally, adding a small amount of ammonia water, heating the solution to 90-100 ℃, preserving the temperature for 10-30 min, maintaining the pH value of the solution at 8-9, and breaking hydrogen bonds in Ce (OH)3O & OH to completely oxidize the Ce (OH)3O & OH into Ce (OH)4, wherein when the pH value is 8-9, no precipitate is formed on heavy metal ions such as Mg2+, and the like, so that the generation of impurities in the Ce (OH)4 can be reduced.

2. The preparation method of the high-purity cerium hydroxide disclosed by the invention is short in process flow, simple in main process equipment, easy to control in operation conditions and high in industrial popularization value, the prepared cerium hydroxide product is high in purity, the purity of the prepared cerium hydroxide reaches over 99%, non-rare earth impurities meet the requirements of TFT-LCD, OLED, LCOS, automobile exhaust purifying agents and IT industry, and finally the ammonium nitrate mother liquor can be recycled to prepare ammonium nitrate byproducts, so that the preparation method is clean and environment-friendly.

Drawings

In order to make the object, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:

FIG. 1 is a flow chart illustrating a method for preparing high purity cerium hydroxide according to the present invention.

Detailed Description

The preferred embodiments of the present invention will be described in detail below.

Example 1

A preparation method of high-purity cerium hydroxide comprises the following steps:

A. quantitatively putting cerium carbonate with the purity of more than 99.99% into a reaction kettle, adding nitric acid for dissolving and heating to obtain a cerium nitrate solution with the acidity of 0.8-1 mol/L, wherein the molar ratio of Ce3+ to NO 3-in the cerium carbonate and the nitric acid is 1: 3;

B. putting the cerium nitrate solution into a primary closed filter tank, filtering the cerium nitrate solution by using a plate frame, then putting the filtered cerium nitrate solution into a secondary closed filter tank for secondary filtration, and then removing oil from the cerium nitrate solution filtered by using ultrasonic waves, wherein double-layer filter cloth is arranged in each of the primary closed filter tank and the secondary closed filter tank, filter paper is padded between the double-layer filter cloth, and the mesh number of the double-layer filter cloth is 200 meshes;

E. adding hydrogen peroxide and a small amount of ammonia water slowly into the cerium nitrate filtrate, adding the hydrogen peroxide and the ammonia water into the cerium nitrate filtrate while stirring, so that Ce (NO3)3 is oxidized into Ce (OH)3 O.OH, the temperature of the reaction system is controlled at 35 ℃, the oxidation time is controlled at 30min, the pH value of the solution system is maintained at 5, then stirring the solution and adding ammonia water to maintain the pH value of the solution at 6, so that Ce (NO3)3 is fully oxidized into Ce (OH)3 O.OH, finally adding a small amount of ammonia water, heating the solution to 90 ℃, keeping the temperature for 10min, maintaining the pH value of the solution at 8, so that Ce (OH)3 O.OH is completely converted into Ce (OH)4, reducing heavy metal precipitation, removing redundant hydrogen peroxide, wherein the molar ratio of the addition amount of the hydrogen peroxide to the addition amount of the cerium nitrate is 2:1, the mass ratio of the total amount of the hydrogen peroxide to the total amount of the ammonia water is 1.20:1, and the ammonia water is cold ammonia water at the temperature of 10 ℃;

F. the Ce (OH)4 precipitate is put into a filter tank to be washed by water once and then washed by absolute ethyl alcohol once, and the washed Ce (OH)4 precipitate is filtered and pumped to dryness by a plate frame under certain pressure to prepare a filter cake;

G. and transferring the filter cake into an oven, drying for 24 hours in a constant-temperature flash evaporation dryer at 90-95 ℃ to obtain a high-purity cerium hydroxide product, and packaging the dried high-purity cerium hydroxide product by adopting two layers of plastic inner films.

Example 2

Example 2 differs from example 1 in that the mesh number of the double-layer filter cloth in step B is 300 mesh.

Example 3

Example 3 differs from example 1 in that, in step E, hydrogen peroxide and a small amount of ammonia water are slowly added to the cerium nitrate filtrate, the hydrogen peroxide and the ammonia water are added to the cerium nitrate filtrate while stirring, so that Ce (NO3)3 is oxidized into Ce (OH)3O · OH, the temperature of the reaction system is controlled at 32 ℃, the oxidation time is controlled at 60min, the PH value of the solution system is maintained at 6, then the solution is stirred and added with the ammonia water to maintain the PH value of the solution at 7, so that Ce (NO3)3 is fully oxidized into Ce (OH)3O · OH, finally, a small amount of ammonia water is added, the solution is heated to 95 ℃ and kept at the temperature for 30min, the PH value of the solution is maintained at 8, so that Ce (OH)3O · OH is completely converted into Ce (OH)4, heavy metal precipitation is reduced, and excess hydrogen peroxide is removed, wherein the molar ratio of the addition amount of hydrogen peroxide to the addition amount of cerium nitrate is 4:1, and the mass ratio of the total amount of hydrogen, the ammonia water is cold ammonia water with the temperature of 15 ℃.

Example 4

Example 4 is different from example 1 in that hydrogen peroxide and a small amount of ammonia water are slowly added into cerium nitrate filtrate, the hydrogen peroxide and the ammonia water are added into the cerium nitrate filtrate while stirring, so that Ce (NO3)3 is oxidized into Ce (OH)3 O.OH, the temperature of a reaction system is controlled to be 35 ℃, the oxidation time is controlled to be 30min, the pH value of the solution system is maintained to be 6, then the solution is stirred and added with the ammonia water to maintain the pH value of the solution to be 7, so that Ce (NO3)3 is fully oxidized into Ce (OH)3 O.OH, finally, a small amount of ammonia water is added, the solution is heated to 90 ℃ and kept for 10min, the pH value of the solution is maintained to be 8.5, the molar ratio of the adding amount of the hydrogen peroxide to the adding amount of the cerium nitrate is 2:1, the mass ratio of the adding amount of the hydrogen peroxide to the total amount of the ammonia water is 1.20:1, the ammonia water is cold ammonia water with the temperature of 10 ℃.

Example 5

Example 5 differs from example 3 in that in step E, hydrogen peroxide and a small amount of ammonia water are slowly added to the cerium nitrate filtrate, the hydrogen peroxide and the ammonia water are added to the cerium nitrate filtrate while stirring, so that Ce (NO3)3 is oxidized into Ce (OH)3O · OH, the temperature of the reaction system is controlled at 32 ℃, the oxidation time is controlled at 60min, the PH of the solution system is maintained at 5, then the solution is stirred and added with the ammonia water to maintain the PH of the solution at 6, so that Ce (NO3)3 is fully oxidized into Ce (OH)3O · OH, finally, a small amount of ammonia water is added, the solution is heated to 95 ℃ and kept at temperature for 30min, the PH of the solution is maintained at 9, so that Ce (OH)3O · OH is completely converted into Ce (OH)4, heavy metal precipitation is reduced, and excess hydrogen peroxide is removed, wherein the molar ratio of the addition amount of hydrogen peroxide to the addition amount of cerium nitrate is 4:1, and the mass ratio of the total amount of hydrogen peroxide to the total amount, the ammonia water is cold ammonia water with the temperature of 15 ℃.

Example 6

Example 6 differs from example 4 in that step F the ce (oh)4 precipitate was washed once with pure water in the filter tank.

Example 7

Example 7 differs from example 6 in that step F the ce (oh)4 precipitate was washed twice with pure water in a filter tank and then twice with absolute ethanol.

Comparative example

The difference between the comparative example and the example 4 is that in the step E, ammonia water is slowly added into the cerium nitrate filtrate, the pH value of the solution is adjusted to 7-8, a proper amount of hydrogen peroxide is added, and the mixture is heated to obtain a mixed solution, wherein the mass ratio of the total amount of the hydrogen peroxide to the total amount of the ammonia water is 1.20: 1.

The oxidation rate, yield, heavy metal impurity mass fraction and HNO3 solubility of the high-purity cerium hydroxide prepared in examples 1-7 and comparative example are shown in the table I.

Watch 1

As can be seen from the table I, the oxidation rate of the high-purity cerium hydroxide prepared by the preparation method of the high-purity cerium hydroxide is kept above 98%, the yield is stabilized between 96% and 98%, the mass fraction of heavy metal is stabilized between (23% and 25) × 10 < -6 >, the HNO3 solubility of the product is good, the non-rare earth impurities of the prepared high-purity cerium hydroxide product meet the requirements of TFT-LCD, OLED, LCOS, automobile exhaust purifying agent and IT industry, and finally the ammonium nitrate mother liquor can be recycled to prepare ammonium nitrate byproducts, so that the preparation method is clean and environment-friendly.

Finally, it is noted that the above-mentioned preferred embodiments illustrate rather than limit the invention, and that, although the invention has been described in detail with reference to the above-mentioned preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the scope of the invention as defined by the appended claims.

Claims

1. The preparation method of high-purity cerium hydroxide is characterized by comprising the following steps of:

2. The method of preparing high purity cerium hydroxide according to claim 1, wherein the molar ratio of Ce3+ to NO3 "in the cerium carbonate and nitric acid of step a is 1: 3.

3. The method for preparing high purity cerium hydroxide according to claim 2, wherein the primary closed filtration tank and the secondary closed filtration tank of step B are both provided with double-layer filter cloth, and filter paper is padded between the double-layer filter cloth.

4. The method for preparing high purity cerium hydroxide according to claim 3, wherein the mesh number of the double-layer filter cloth in step B is 200-300 mesh.

5. The method for preparing high-purity cerium hydroxide according to claim 4, wherein the molar ratio of the added amount of hydrogen peroxide to the added amount of cerium nitrate in the step E is (2-4): 1, and the mass ratio of the total amount of hydrogen peroxide to ammonia water is (1.20-1.25): 1.

6. The method for preparing high purity cerium hydroxide according to claim 5, wherein the ammonia water of step E is cold ammonia water of 10 to 15 ℃.

7. The method for preparing high-purity cerium hydroxide according to claim 6, wherein in the step E, oxygen or ozone is introduced as an auxiliary oxidant in the process of slowly adding hydrogen peroxide into the cerium nitrate filtrate.

8. The method for preparing high-purity cerium hydroxide according to claim 7, wherein the step E of adding hydrogen peroxide to the cerium nitrate filtrate while stirring.

9. The method of claim 8, wherein step F comprises washing the ce (oh)4 precipitate with water in a filter tank and then with absolute ethanol.

10. The method of claim 9, wherein the high purity cerium hydroxide product dried in step G is packaged with two plastic inner films.