CN113249597A

CN113249597A - Method for purifying rare earth solution

Info

Publication number: CN113249597A
Application number: CN202010961190.9A
Authority: CN
Inventors: 刘钧云; 王功秒; 陈华斌; 刘昭优; 刘深山; 叶辉兴
Original assignee: Jiangxi Mingda Functional Materials Co ltd
Current assignee: Jiangxi Mingda Functional Materials Co ltd
Priority date: 2020-09-14
Filing date: 2020-09-14
Publication date: 2021-08-13

Abstract

The invention discloses a purification method of a rare earth solution, belonging to the technical field of rare earth separation. Adding calcium-containing substances or barium compounds into a rare earth solution step by step and filtering respectively; obtaining barium sulfate and rare earth purifying liquid. The method not only effectively reduces the content of impurities such as sulfate radicals in the rare earth purification liquid, optimizes the process conditions of subsequent extraction production, but also recovers barium sulfate, reduces the generation of waste residues, reduces the toxicity of the waste residues, reduces the chance of contacting toxic substances for operating personnel, facilitates the treatment and management of calcium residues without barium elements, and avoids environmental pollution; the process conditions of the subsequent working section are optimized, and meanwhile, useful substances are comprehensively recovered, so that better economic benefit and social benefit are realized.

Description

Method for purifying rare earth solution

Technical Field

The invention relates to a method for purifying rare earth solution and comprehensively recovering byproducts, belonging to the technical field of rare earth separation.

Background

In the process of mining the ionic rare earth ore, the ammonium sulfate has strong selectivity to leached ions, so that Ca can be effectively reduced² ⁺、Mg ²⁺For leaching of harmful metal ions, ammonium sulfate is usually used as a leaching agent, and the obtained mixed rare earth compound contains a small amount of sulfate.

These mixed rare earth compounds containing small amounts of sulfate are usually converted to mixed rare earth chloride solutions and then extracted and separated into single rare earth compounds or concentrates using acidic phosphorus extractants. But these sulfates will adversely affect extraction production.

At present, rare earth production enterprises mostly adopt a method of adding alkaline substances for neutralization to adjust the pH value of a mixed rare earth chloride solution, then add a proper amount of soluble barium compounds to convert sulfate radicals in the mixed rare earth chloride solution into barium sulfate, and finally filter and remove all insoluble substances once so as to meet the requirements of extraction production on impurities as much as possible. In order to reduce the cost, the alkaline substance is mostly lime, calcium carbonate and other cheap neutralizing agents.

The chinese patent application published on 2015, 02/04, publication No. CN104328290A (referred to as prior art 1) discloses an acid leaching process for ionic rare earth concentrate, which comprises performing primary acid leaching on the ionic rare earth concentrate, controlling the pH of a reaction system at 2-3, and performing solid-liquid separation to obtain primary slag and primary leachate; performing secondary acid leaching on the primary slag, controlling the pH value of a reaction system to be less than or equal to 1, and performing solid-liquid separation to obtain secondary slag and secondary leachate; returning the secondary leachate to be used for primary acid leaching; the technical scheme that the primary leachate is neutralized and purified, impurities such as sulfate radicals, iron, aluminum, radioactive substances, heavy metals and the like are removed step by step, and then neutralized slag and rare earth solution are obtained through solid-liquid separation achieves the technical effects that the rare earth content of secondary slag treated by the acid leaching process is less than 5%, the slag amount is less than 7% of the input amount of ionic rare earth oxide concentrate, the rare earth leaching yield is more than 99%, the total radioactivity specific activity of the secondary leaching slag is less than 7.4 multiplied by 104Bq/kg, the slag release is low, and the storage difficulty is reduced.

Therefore, because a plurality of insoluble substances are filtered at one time, the finally filtered neutralized slag contains a large amount of calcium sulfate and barium sulfate. The mixed insoluble substance which takes barium sulfate and calcium sulfate as main components has low content of single substance, is not only toxic, but also has extremely low value, is inconvenient for storage and transportation and is difficult to recycle. With the increase of the amount, not only the resources such as barium are wasted, but also the secondary pollution is easily caused. And the content of sulfate radical in the mixed rare earth chloride solution prepared by the process method is 0.4-1.5g/L, and adverse effects such as a third phase and the like are easily generated in the extraction separation process.

Disclosure of Invention

In order to reduce the content of sulfate radical impurities in the mixed rare earth chloride solution, recycle resources in insoluble substances, reduce the discharge amount of waste residues and overcome the defects in the prior art, the invention adopts the following technical scheme:

a method for purifying a rare earth solution, comprising the steps of:

detecting the residual acid and sulfate radical content of the rare earth solution;

adding a barium compound or an alkaline substance into the rare earth solution, and filtering to obtain an intermediate feed liquid and filter residue I;

and step three, adding an alkaline substance or a barium compound into the intermediate feed liquid, and filtering to obtain a rare earth purified liquid and filter residue II.

In one preferable technical scheme of the invention, in the step one, the alkaline substance is at least one of quicklime, slaked lime and calcium carbonate.

According to another preferable technical scheme of the invention, the barium compound in the second step is at least one of barium chloride, barium carbonate, barium nitrate, barium acetate and barium hydroxide.

According to another preferable technical scheme, the first filter residue or the second filter residue is barium sulfate.

In another preferable technical scheme, the method further comprises the step of dissolving the rare earth compound with acid and then filtering before the step one to obtain a rare earth solution and an acid insoluble substance.

In another preferable technical scheme, the method further comprises the step of dissolving the filtered acid insoluble substances by using acid or acid and an oxidizing agent again.

In another preferable technical scheme of the invention, the barium chloride is added into the intermediate feed liquid in a solid and/or solution form.

In another preferable technical scheme of the invention, the acid-soluble impurities are removed from the barium sulfate through acid washing.

According to the method, barium compounds are sequentially added into the rare earth solution to remove sulfate radicals or alkaline substances are added to serve as neutralizing agents to regulate residual acid of the solution, and acid insoluble substances, barium sulfate and calcium slag are respectively separated through step-by-step filtration, so that the content of impurities such as sulfate radicals in the rare earth purified solution is effectively reduced, and the process conditions of subsequent extraction production are optimized; the neutralization slag is separated into barium sulfate and calcium slag, so that the barium sulfate is recovered, the quantity of waste slag is reduced, the toxicity of the calcium slag is reduced, the possibility that operators contact toxic substances is reduced, the calcium slag without barium is convenient to treat and manage, and the environmental pollution is avoided; the process conditions of the subsequent working section are optimized, and meanwhile, useful substances are comprehensively recovered, so that better economic benefit and social benefit are realized.

Drawings

FIG. 1 is a schematic view of the process of purifying and comprehensively recycling the rare earth solution of the present invention.

Detailed Description

The present invention is further illustrated by the following specific examples.

Example one

And dissolving the mixed rare earth oxide by using hydrochloric acid, and filtering and separating acid insoluble substances to obtain a mixed rare earth chloride solution. The main components of the mixed rare earth chloride solution are detailed in the table I.

Measuring the content of sulfate radical in the mixed rare earth chloride solution, and adding solid barium chloride and/or barium chloride solution according to the molar ratio of 90%.

And (3) measuring the sulfate radical content in the solution again, and if the sulfate radical content is more than or equal to 0.1g/L, then performing secondary determination according to the molar ratio of barium chloride: sulfate group (0.9-1): 1 adding barium chloride solution until the content of sulfate radicals is less than or equal to 0.1 g/L.

Filtering to obtain crude barium sulfate and intermediate feed liquid.

Adding appropriate amount of calcium carbonate into the intermediate liquid, adjusting pH of the residual acid to 3.5-4.5, and filtering to obtain rare earth purified liquid and calcium residue. The calcium carbonate can also be replaced by caustic soda, ammonia water, sodium carbonate, etc., and the calcium content in the calcium slag is reduced.

The crude barium sulfate is washed by acid and water respectively, and impurities such as rare earth and the like carried in the crude barium sulfate are removed to obtain the barium sulfate.

The barium chloride may be replaced by barium nitrate, barium acetate, barium hydroxide and/or barium carbonate. When barium carbonate is used instead of barium chloride, the amount of alkaline substances such as calcium carbonate for adjusting residual acid can be reduced, and the amount of waste residues can be further reduced.

The main components of the mixed rare earth chloride solution, the intermediate feed liquid and the rare earth purifying liquid are detailed in a table I, and the main components of the barium sulfate and the calcium slag are detailed in a table II.

Watch I (unit: g/l)

Name (R)	SO₄ ^2-	REO	SiO₂	Fe₂O₃	CaO	Al₂O₃
							Mixed rare earth chloride solution	1.789	254	0.528	0.795	5.401	0.983
Intermediate feed liquid	0.021	246	0.508	0.787	5.230	0.951
							Rare earth purifying liquid	0.021	245	0.061	0.022	10.34	0.518

TABLE II (Unit: wt%)

Name (R)	BaSO₄	REO	Fe₂O₃	CaO	Al₂O₃	Others
							Calcium slag	＜0.1	1.46	11.92	22.02	13.62	50.98
Barium sulfate	98.02	0.22	0.004	0.17	0.16	1.43

The recovered barium sulfate basically meets the relevant indexes of GB/T2899-once 2017 of industrial precipitated barium sulfate, and meets the use requirements of relevant enterprises.

In this example barium chloride was used to precipitate the sulphate and calcium carbonate was used as the neutralising agent to adjust the residual acid of the solution. The sulfate radical content in the intermediate feed liquid and the rare earth purifying liquid is low and stable.

The barium chloride is added in several times, so that the barium chloride is prevented from being excessive, and unnecessary consumption of the barium chloride is reduced. And simultaneously, barium chloride is prevented from entering raffinate to finally pollute the environment.

The barium sulfate and the calcium slag are respectively filtered, so that the residual sulfate radical content in the finally obtained rare earth purifying liquid can be stabilized at a lower level without increasing. The amount of the third phase produced during the subsequent extractive separation is reduced by more than 1/3.

Comparative example

The mixed rare earth chloride solution of example one was reacted with 100% of the theoretical amount of calcium oxide required for precipitation of sulfate as described in example 1 of Prior Art 1 for 10 minutes, and then 50% of BaCl was added to precipitate sulfate₂And immediately performing solid-liquid separation and washing to obtain neutralized slag and a rare earth chloride solution. Filtrate 1 at the 2 nd minute after the start of filtration, filtrate 2 at the 30 th minute, filtrate 3 at the 120 th minute, and the total amount of filtration were measuredImpurities such as sulfate radicals and the like in the obtained rare earth chloride solution are obtained, and the related detection data of the rare earth chloride solution and the like are shown in the third table; the detection data related to the neutralized slag are shown in the fourth table. As can be seen from Table I, the sulfate concentration in the solution to be filtered gradually increased with time after the addition of barium chloride.

Watch III (unit: g/l)

Name (R)	SO₄ ^2-	REO	SiO₂	Fe₂O₃	CaO	Al₂O₃
							Filtrate 1	0.034
Filtrate 2	0.304
							Filtrate 3	0.399
Rare earth chloride solution	0.392	251	0.062	0.032	10.54	0.531

TABLE IV (Unit: wt%)

Name (R)	BaSO₄	REO	Fe₂O₃	CaSO₄	Al₂O₃	Others
							Neutralizing slag	49.01	2.57	0.76	31.88	2.46	13.32

The quantity of the neutralized slag is more than 2 times of that of the calcium slag in the embodiment.

Example two

And dissolving the mixed rare earth carbonate with hydrochloric acid to obtain a mixed rare earth chloride solution. The relevant components of the mixed rare earth chloride solution are detailed in the fifth table.

Adding a proper amount of barium chloride according to the content of sulfate radicals in the mixed rare earth chloride solution, and measuring the content of the sulfate radicals in the solution again, wherein if the content of the sulfate radicals is more than or equal to 0.1g/L, the molar ratio of the barium chloride to the sulfate radicals is 1: 1 adding barium chloride solution until the content of sulfate radicals is less than or equal to 0.1 g/L.

Filtering to obtain intermediate feed liquid and filter residue. Washing the filter residue to obtain barium sulfate.

Adding a proper amount of carbide slag into the intermediate feed liquid according to the concentration of the residual acid, adjusting the pH value of the residual acid to about 3.5, and filtering to obtain rare earth purified liquid and calcium slag. If necessary, flocculating agents such as polyacrylamide and the like can be added in a proper amount before filtration to improve the filtration condition. The main components of the calcium slag are shown in the sixth table.

The components of the rare earth purifying liquid are detailed in a fifth table, and the main components of the barium sulfate are detailed in a fourth table. When the iron and aluminum impurity content of barium sulfate is relatively high, the barium sulfate may be washed with an acid before washing with water.

The main impurities of the carbide slag are free carbon and water, the content of calcium hydroxide in dry basis components can reach more than 99 percent, and the impurities are few.

Watch five (unit: g/l)

Name (R)	SO₄ ^2-	REO	SiO₂	Fe₂O₃	CaO	Al₂O₃
							Mixed rare earth chloride solution	2.682	158	0.801	1.021	6.612	1.385
Intermediate feed liquid	0.037	147	0.743	0.948	6.151	1.286
							Rare earth purifying liquid	0.037	146	0.060	0.041	10.56	0.755

Watch six (unit: wt%)

Name (R)	BaSO₄	REO	Fe₂O₃	CaO	Al₂O₃	Others
							Calcium slag	＜0.1	2.20	16.88	20.75	18.55	41.62
Barium sulfate	95.69	0.27	0.32	0.29	0.35	3.08

EXAMPLE III

And dissolving the mixed rare earth oxide by using hydrochloric acid, and filtering and separating acid insoluble substances to obtain a mixed rare earth chloride solution. The main components of the mixed rare earth chloride solution are detailed in Table seven.

And adding a proper amount of barium chloride into the mixed rare earth chloride solution, and filtering to obtain intermediate feed liquid and first filter residue. And washing the filter residue I to obtain barium sulfate. The main components of the barium sulfate are shown in the table eight in detail.

Adding appropriate amount of lime powder (mixture of calcium oxide and calcium hydroxide) into the intermediate feed liquid, adjusting pH of the residual acid to about 3.5, and filtering to obtain rare earth purified liquid and calcium residue. The main components of the rare earth purifying liquid are detailed in a fifth table, and the main components of the calcium slag are detailed in an eighth table.

Measuring the content of sulfate radical, and adding a proper amount of solution; and (4) measuring the sulfate radical content in the solution again, and if the sulfate radical content is more than or equal to 0.1g/L, adding the barium chloride solution again until the sulfate radical content is less than or equal to 0.1 g/L.

The lime powder is used for adjusting the acidity of the solution and can be replaced by alkaline substances such as magnesium oxide, caustic soda and the like. The barium chloride may be partially or completely replaced by barium carbonate.

Watch five (unit: g/l)

Name (R)	SO₄ ^2-	REO	SiO₂	Fe₂O₃	CaO	Al₂O₃
							Mixed rare earth chloride solution	0.725	232	0.232	0.311	2.55	0.401
Intermediate feed liquid	0.050	231	0.230	0.309	2.53	0.398
							Rare earth purifying liquid	0.051	230	0.050	0.033	9.98	0.052

Watch six (Unit:% by weight)

Name (R)	BaSO₄	REO	Fe₂O₃	CaO	Al₂O₃	Others
							Calcium slag	＜0.1	3.09	11.77	42.99	13.50	28.65
Barium sulfate	95.95	0.18	0.45	1.02	0.51	1.89

And sixthly, most of CaO in the calcium slag is burnt lime in the lime powder.

Example four

In the mixed rare earth chloride solution described in example three, a proper amount of lime powder is added first, and the residual acid is adjusted to about pH 3.5. Filtering to obtain intermediate feed liquid and calcium slag.

Measuring the sulfate radical content in the intermediate feed liquid, and adding a proper amount of barium chloride solution; and measuring the sulfate radical content in the solution again, and if the sulfate radical content is more than or equal to 0.1g/L, adding a proper amount of barium chloride again until the sulfate radical content is less than or equal to 0.1 g/L.

And filtering again to obtain crude barium sulfate and rare earth purified liquid. The main components of the rare earth purifying liquid are detailed in Table seven.

And washing the crude barium sulfate with acid and water to obtain barium sulfate.

The main components of the calcium slag and the barium sulfate are shown in the table eight in detail.

Watch seven (unit: g/l)

Name (R)	SO₄ ^2-	REO	SiO₂	Fe₂O₃	CaO	Al₂O₃
							Mixed rare earth chloride solution	0.725	232	0.232	0.311	2.55	0.401
Intermediate feed liquid	0.632	231	0.050	0.037	11.02	0.398
							Rare earth purifying liquid	0.051	231	0.050	0.033	10.98	0.055

Watch eight (Unit:%)

Name (R)	BaSO₄	REO	Fe₂O₃	CaSO₄	Al₂O₃	Others
							Calcium slag	＜0.1	3.37	11.21	49.63	13.72	12.07
Barium sulfate	95.05	0.18	0.43	1.55	0.65	2.14

CaSO in calcium slag₄Including CaSO₄And over-burnt lime in the lime powder.

Finally, the above embodiments are only for illustrating the technical solutions of the present invention and not for limiting, although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions may be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all of them should be covered in the claims of the present invention.

Claims

1. A method for purifying a rare earth solution, comprising the steps of:

detecting the sulfate radical content of a rare earth solution;

2. The method for purifying a rare earth solution as claimed in claim 1, wherein said alkaline substance in the first step is at least one of quicklime, slaked lime and calcium carbonate.

3. The method for purifying a rare earth solution as claimed in claim 1, wherein said barium compound in the second step is barium chloride and/or barium carbonate.

4. The method for purifying a rare earth solution as claimed in claim 3, wherein the barium chloride is an aqueous solution.

5. The method for purifying a rare earth solution as claimed in claim 1, wherein the first residue or the second residue is barium sulfate.

6. The method for purifying a rare earth solution as claimed in claim 1, wherein the barium sulfate is acid-washed to remove acid-soluble impurities.

7. The method for purifying a rare earth solution as claimed in claim 1, further comprising a step of dissolving the rare earth compound with an acid and then filtering before the step one to obtain a rare earth solution and an acid-insoluble substance.

8. The method for purifying a rare earth solution as claimed in claim 7, further comprising dissolving the filtered acid-insoluble substance again with an acid or an acid and an oxidizing agent.

9. The method for purifying a rare earth solution as claimed in claim 1, wherein the rare earth solution or the intermediate solution is adjusted to pH4 or less by adding an alkaline substance.