阅读说明：本技术 从析钠母液中回收制备电池级锂盐的工艺 (process for recovering and preparing battery-grade lithium salt from sodium-separating mother liquor ) 是由 彭文修 亓亮 胥明 王占前 代文彬 吕延鹏 颜廷利 康如金 武亮 时健 于 2019-09-30 设计创作，主要内容包括：本发明公开了从析钠母液中回收制备电池级锂盐的工艺,包括调配析钠母液,酸化预处理,碱化除杂,冷冻析芒硝,蒸发浓缩得到硫酸锂的浓缩液；再向浓缩液中加入饱和纯碱溶液经过沉锂、离心分离、洗涤、干燥,制得电池级碳酸锂产品；或向浓缩液加入烧碱溶液,经过苛化、冷冻、浓缩结晶、返溶、重结晶、干燥,制得电池级氢氧化锂产品。本发明的工艺可以完全取代析钠母液的传统法制备工业级锂盐的工艺,制备价值更高的电池级碳酸锂和氢氧化锂,升级了产品等级和种类,是锂盐行业的一次重大创新；工艺经济效益显著,操作简单,成本低廉,对于盐湖卤水提锂和矿石提锂的相关企业,都具有普遍的适应性非常适合工业化推广。(The invention discloses a process for recovering and preparing battery-grade lithium salt from sodium-separated mother liquor, which comprises the steps of preparing the sodium-separated mother liquor, carrying out acidification pretreatment, alkalizing to remove impurities, freezing to separate mirabilite, and carrying out evaporation concentration to obtain a concentrated solution of lithium sulfate; adding saturated sodium carbonate solution into the concentrated solution, and performing lithium precipitation, centrifugal separation, washing and drying to obtain a battery-grade lithium carbonate product; or adding caustic soda solution into the concentrated solution, causticizing, freezing, concentrating and crystallizing, re-dissolving, recrystallizing and drying to obtain the battery-grade lithium hydroxide product. The process can completely replace the process for preparing industrial lithium salt by the traditional method of sodium-separating mother liquor, the battery-grade lithium carbonate and lithium hydroxide with higher preparation value are prepared, the grade and the type of the product are upgraded, and the process is a major innovation in the lithium salt industry; the process has obvious economic benefit, simple operation and low cost, has universal adaptability to related enterprises for extracting lithium from salt lake brine and lithium from ores, and is very suitable for industrial popularization.)

1. A method for recovering and preparing battery-grade lithium salt from sodium-separating mother liquor is characterized by comprising the following steps:

(1) Blending: mixing the sodium-separated mother liquor with the mixed liquor, and continuously stirring to obtain a prepared liquor;

(2) Acidifying pretreatment: adding sulfuric acid into the prepared solution for pretreatment, and continuously stirring to obtain acidified solution;

(3) alkalization and impurity removal: sequentially adding caustic soda and soda ash into the acidified solution, continuously stirring, filtering and separating to obtain clear filtrate;

(4) Freezing and separating out mirabilite: freezing and cooling the filtrate, crystallizing to separate out mirabilite, and then performing centrifugal separation to obtain mirabilite and a clear frozen liquid;

(5) And (3) evaporation and concentration: heating, evaporating and concentrating the frozen solution to obtain a concentrated solution;

(6) Preparing a lithium salt: adding saturated sodium carbonate solution into the concentrated solution, and preparing a battery-grade lithium carbonate product through lithium precipitation, centrifugal separation, washing and drying; or adding caustic soda solution into the concentrated solution, causticizing, freezing, concentrating and crystallizing, re-dissolving, recrystallizing and drying to obtain the battery-grade lithium hydroxide product.

2. The method according to claim 1, wherein in the step (1), the compound liquid is any one of a purification completion liquid, a purification liquid and a leaching liquid; the mixing volume ratio of the sodium precipitation mother liquor to the matching liquor is 1: 1-5: 1.

3. The method according to claim 1, wherein in the step (1), the stirring temperature is 50-95 ℃ and the stirring time is 30-120 min.

4. The method according to claim 1, wherein in the step (2), the mass concentration of the sulfuric acid is 10-98%; and the pH value of the acidified solution is 1-6.

5. the method according to claim 1, wherein in the step (3), the stirring temperature is 80-95 ℃ and the stirring time is 30-120 min.

6. The method according to claim 1, wherein in the step (3), the pH of the clear filtrate is 10-13, the concentration of OH ^- in the clear filtrate is 0.1-0.5 g/L, and the concentration of CO ₃ ^2- in the clear filtrate is 0.5-2.0 g/L.

7. the method according to claim 1, wherein the freezing temperature in step (4) is-20 ℃ to 0 ℃.

8. The method according to claim 1, wherein in the step (5), the concentration of Li ⁺ in the concentrated solution is 15-30 g/L.

9. The method according to claim 1, wherein in the step (6), the temperature of the lithium deposition is 80-95 ℃; the liquid-solid volume ratio of the washing is 1: 1-6: 1.

10. The method according to claim 1, wherein in the step (6), the mass concentration of the caustic soda solution is 30-70%, and the causticizing temperature is 80-95 ℃; the solid-liquid volume ratio of recrystallization is 1: 1-1: 10.

Technical Field

The invention relates to the technical field of lithium salt production, in particular to a process for recovering and preparing battery-grade lithium salt from sodium precipitation mother liquor.

Background

The lithium salt for preparing the lithium battery positive electrode material mainly comprises battery grade lithium carbonate and lithium hydroxide. Lithium carbonate is a basic material for producing secondary lithium salts and lithium metal products, is not only applied to civil fields such as aluminum smelting, glass and ceramics, but also widely applied to high-tech fields such as medicine, new energy, energy storage and the like, so that the lithium carbonate becomes a lithium raw material with the largest consumption in the lithium industry, and other lithium products are basically downstream products of lithium carbonate. The lithium hydroxide can be used in the basic chemical fields of lithium soap, lithium-based lubricating grease and the like, can also be used in the fine chemical fields of a spectral analysis developing agent, a photographic developer and the like, and can also be used in the military industry fields of metal lithium, atomic energy and the like.

the production process of lithium salt can be divided into salt lake brine extraction and ore extraction according to different raw material sources. Salt lake brine extraction process is mainly adopted in south and American areas abroad, and spodumene ore extraction process is mainly adopted in other areas including China.

In the process of preparing lithium salt from spodumene ore, roasting, acidifying, size mixing and leaching are firstly required, and leaching solution is generated in the process; then purifying, evaporating and concentrating to respectively obtain purified liquid and purified finished liquid; and then, producing lithium salt, obtaining lithium precipitation mother liquor during lithium precipitation, and obtaining anhydrous sodium sulfate and sodium precipitation mother liquor after the lithium precipitation mother liquor is neutralized by sulfuric acid and evaporated and crystallized. Because the lithium precipitation mother liquor and the sodium separation mother liquor both contain a certain amount of lithium, the improvement of the recovery rate of lithium in the lithium precipitation mother liquor and the sodium separation mother liquor in the lithium salt industry is one of the keys for reflecting the core competitiveness of enterprises and creating more economic benefits.

201910341935.9 method for treating lithium carbonate precipitation mother liquor, 201711439162.5 method for producing battery-grade lithium hydroxide from battery-grade lithium carbonate precipitation mother liquor, 201710152049.2 method for recovering lithium from lithium precipitation mother liquor into battery-grade lithium carbonate, wherein the patents disclose methods for recovering lithium salt from lithium precipitation mother liquor, lithium in lithium precipitation mother liquor exists mainly in the form of Li ₂ CO ₃, and the solubility is low, SO that the concentration of Li ⁺ in the solution is low, thereby limiting the recovery rate of lithium, the lithium precipitation mother liquor is neutralized by sulfuric acid and evaporated to obtain anhydrous sodium sulfate and sodium precipitation mother liquor, the sodium precipitation mother liquor mainly contains Na ₂ SO ₄ with extremely high concentration, the concentration of Na is as high as 380g/L, the lithium in the sodium precipitation mother liquor exists mainly in the form of Li ₂ SO ₄, but the concentration of Li ⁺ is only 9g/L, the recovery rate is relatively low, the recovery rate of lithium is not high, the sodium precipitation mother liquor is prepared continuously, the lithium ion recovery rate is high, the lithium ion recovery rate is relatively low, the lithium ion recovery rate is relatively high, the lithium precipitation mother liquor is relatively high, and the recovery rate is relatively high.

Disclosure of Invention

aiming at the defects of the prior art, the invention provides a method for recovering and preparing battery-grade lithium salt from sodium-separating mother liquor, and the process has the advantages of simple operation and low cost, and is very suitable for industrial popularization.

The invention is realized by the following technical scheme: a process is provided for recovering a battery grade lithium salt from a sodium-evolving mother liquor, said process comprising the steps of:

(1) Blending: mixing the sodium-separated mother liquor with the mixed liquor, and continuously stirring to obtain a prepared liquor;

(2) Acidifying pretreatment: adding sulfuric acid into the prepared solution for pretreatment, and continuously stirring to obtain acidified solution;

(3) Alkalization and impurity removal: sequentially adding caustic soda and soda ash into the acidified solution, continuously stirring, filtering and separating to obtain clear filtrate;

(4) freezing and separating out mirabilite: freezing and cooling the filtrate, crystallizing to separate out mirabilite, and then performing centrifugal separation to obtain mirabilite and a clear frozen liquid;

(5) And (3) evaporation and concentration: heating, evaporating and concentrating the frozen solution to obtain a concentrated solution;

(6) Preparing a lithium salt: adding saturated sodium carbonate solution into the concentrated solution, and preparing a battery-grade lithium carbonate product through lithium precipitation, centrifugal separation, washing and drying; or adding caustic soda solution into the concentrated solution, causticizing, freezing, concentrating and crystallizing, re-dissolving, recrystallizing and drying to obtain the battery-grade lithium hydroxide product.

Preferably, in the step (1), the compounding solution is any one of a purification completion solution, a purification solution and an extraction solution; the mixing volume ratio of the sodium precipitation mother liquor to the matching liquor is 1: 1-5: 1.

preferably, in the step (1), the stirring temperature is 50-95 ℃, and the stirring time is 30-120 min.

Preferably, in the step (2), the mass concentration of the sulfuric acid is 10-98%; and the pH value of the acidified solution is 1-6.

Preferably, in the step (3), the stirring temperature is 80-95 ℃, and the stirring time is 30-120 min.

Preferably, in the step (3), the pH of the clear filtrate is 10-13, the concentration of OH ^- in the clear filtrate is 0.1-0.5 g/L, and the concentration of CO ₃ ^2- in the clear filtrate is 0.5-2.0 g/L.

Preferably, in the step (4), the freezing temperature is-20 ℃ to 0 ℃.

preferably, in the step (5), the concentration of Li ⁺ in the concentrated solution is 15-30 g/L.

Preferably, in the step (6), the temperature of the lithium deposition is 80-95 ℃; the liquid-solid volume ratio of the washing is 1: 1-6: 1.

Preferably, in the step (6), the mass concentration of the caustic soda solution is 40-70%, and the causticizing temperature is 80-95 ℃; the solid-liquid volume ratio of recrystallization is 1: 1-1: 10.

The invention has the beneficial effects that:

1. The process for recovering and preparing the battery-grade lithium salt from the sodium separation mother liquor can completely replace the process for preparing the industrial-grade lithium salt by the traditional method of the sodium separation mother liquor, prepare the battery-grade lithium carbonate and the lithium hydroxide with higher value, upgrade the product grade and improve the lithium recovery rate; the traditional method can only prepare industrial-grade lithium carbonate products, and the freezing method can prepare battery-grade lithium carbonate and lithium hydroxide with higher value.

2. The invention relates to a process for recovering and preparing battery-grade lithium salt from sodium-separating mother liquor, which adopts the methods of acidification pretreatment, alkalization impurity removal and freezing mirabilite separation to obtain lithium sulfate solution with extremely high purity, thereby preparing the battery-grade lithium salt with extremely high grade.

3. The process for recovering and preparing the battery-grade lithium salt from the sodium-separating mother liquor has the advantages of remarkable economic benefit, simple operation and low cost, and has universal adaptability to enterprises related to lithium extraction from salt lake brine and lithium extraction from ores at home and abroad.

4. The process for recovering and preparing the battery-grade lithium salt from the sodium-separating mother liquor has the advantages of simple operation, low cost and obvious economic benefit, and is very suitable for industrial popularization.

drawings

FIG. 1 is a flow chart of the present invention for recovering and preparing battery grade lithium salt from sodium precipitation mother liquor;

Detailed Description

Interpretation of terms:

Leaching solution: in the process of preparing lithium salt from spodumene ore, roasting, acidifying, mixing and leaching spodumene to obtain leaching solution, wherein typical values of main components of the leaching solution are shown in table 1;

Purifying liquid: sequentially adding caustic soda and soda ash into the leaching solution to remove impurities such as calcium, magnesium and the like, and performing liquid-solid separation to obtain a solution which is a purifying solution, wherein typical values of main components of the purifying solution are shown in table 1;

and (3) purifying the finished solution: evaporating and concentrating the purified liquid to obtain purified liquid, wherein typical values of main components of the purified liquid are shown in table 1;

lithium deposition mother liquor: precipitating lithium from the purified solution by using soda ash, and performing liquid-solid separation to obtain a solution as a lithium precipitation mother solution, wherein typical values of main components of the lithium precipitation mother solution are shown in table 1;

Sodium separation mother liquor: the lithium precipitation mother liquor is neutralized by acid, evaporated and crystallized, and then anhydrous sodium sulfate is separated, the rest is sodium precipitation mother liquor, and typical values of main components of the sodium precipitation mother liquor are shown in table 1.

TABLE 1 typical values of principal components

name (R)	Component (A)	Li+	K+	Na+	Ca2+	Mg2+	CO3 2-	SO4 2-	Cl-
										Leaching solution	content g/L	14.6	0.8	6.0	0.015	0.0008	0.06	118.2	0.3
Purifying liquid	Content g/L	14.1	0.7	5.6	0.0040	0.0001	0.5	100.6	0.2
										Purification completion liquid	content g/L	25.8	1.6	10.4	0.0072	0.0002	0.7	216.8	0.4
Lithium deposition mother liquor	content g/L	2.9	1.0	70.5	0.0056	0.0002	12.6	145.8	0.3
										Mother liquor for sodium separation	Content g/L	8.6	28.4	110.5	0.002	0.0002	1.5	298.2	25.6

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

as described in the background art, lithium in the sodium precipitation mother liquor exists in the form of lithium sulfate, but the sodium precipitation mother liquor has a large impurity content, and cannot be directly used for preparing battery-grade lithium salt. Based on the above, the invention provides a process for recovering and preparing battery-grade lithium salt from sodium-separating mother liquor, which comprises the following steps:

(1) Blending: mixing the sodium-separated mother liquor with the mixed liquor, and continuously stirring to obtain a prepared liquor;

(2) Acidifying pretreatment: adding sulfuric acid into the prepared solution for pretreatment, and continuously stirring to obtain acidified solution;

(3) alkalization and impurity removal: sequentially adding caustic soda and soda ash into the acidified solution, continuously stirring, filtering and separating to obtain clear filtrate;

(4) freezing and separating out mirabilite: freezing and cooling the filtrate, crystallizing to separate out mirabilite, and then performing centrifugal separation to obtain mirabilite and a clear frozen liquid;

(5) And (3) evaporation and concentration: heating, evaporating and concentrating the frozen solution to obtain a concentrated solution;

(6) Preparing a lithium salt: adding saturated sodium carbonate solution into the concentrated solution, and preparing a battery-grade lithium carbonate product through lithium precipitation, centrifugal separation, washing and drying; or adding caustic soda solution into the concentrated solution, causticizing, freezing, concentrating and crystallizing, re-dissolving, recrystallizing and drying to obtain the battery-grade lithium hydroxide product.

In the step (1), the sodium precipitation mother liquor is mixed with one of the purification completion liquor, the purification liquor and the leaching liquor, so that on one hand, the concentration of lithium sulfate in the purification completion liquor, the purification liquor and the leaching liquor is higher than that of the sodium precipitation mother liquor, and lithium can be supplemented to the sodium precipitation mother liquor, thereby improving the comprehensive recovery rate of lithium; on the other hand, the impurity amount and the impurity content of the purification completion liquid, the purification liquid and the leaching liquid are less than those of the sodium precipitation mother liquid, and the purification completion liquid, the purification liquid and the leaching liquid have certain purification effect on the sodium precipitation mother liquid.

in the step (2), the sulfuric acid is added because the blending solution contains more impurity ions such as CO ₃ ^2- and the like, so that the subsequent lithium precipitation reaction is influenced, and CO ₃ ^2- and the sulfuric acid are removed through chemical reaction.

in the step (3), the caustic soda and the soda ash are sequentially added because the acidified solution contains more metal impurity ions such as Mg ²⁺, Fe ³⁺, Ca ²⁺ and the like, the caustic soda and the soda ash can react with the acidified solution to generate precipitates such as magnesium hydroxide, ferric hydroxide, calcium carbonate and the like, and impurities are removed after filtration, so that the purification effect is achieved.

in the step (4), after freezing, the sodium sulfate in the solution is separated out as Na ₂ SO ₄.10H ₂ O (also called mirabilite), and the mirabilite can simultaneously carry away and remove a large amount of K ⁺ and Cl ^- , SO that the impurity content is further reduced, and the lithium sulfate is mainly contained in the residual solution, and the lower the impurity content is, the higher the quality of lithium salt can be prepared.

In the step (5), the solution containing lithium sulfate is concentrated to improve the recovery rate of lithium in the subsequent preparation of a lithium salt.

And (6) adding a saturated sodium carbonate solution when preparing lithium carbonate, so that lithium sulfate reacts with sodium carbonate to generate lithium carbonate precipitate, performing centrifugal separation to obtain a crude lithium carbonate product, washing the crude lithium carbonate product for multiple times to obtain a wet lithium carbonate product, and drying to obtain the battery-grade lithium carbonate. When preparing lithium hydroxide, adding caustic soda solution to causticize lithium sulfate solution completely, freezing to separate out mirabilite, thus obtaining solution mainly containing lithium hydroxide, evaporating, concentrating and crystallizing the solution to obtain a crude lithium hydroxide product, dissolving the crude lithium hydroxide product in water again, evaporating, concentrating and recrystallizing to obtain a wet lithium hydroxide product, and drying to obtain the battery-grade lithium hydroxide.

It can be seen from table 1 that the sodium precipitation mother liquor contains other ions besides Li ⁺, mainly Na ⁺, K ⁺, Ca ²⁺, Mg ²⁺, Fe ³⁺, CO ₃ ^2- , SO ₄ ^2- , Cl ^- , wherein the ions of CO ₃ ^2- , Ca ²⁺, Mg ²⁺, Fe ³⁺ are insoluble in water after being precipitated to form impurities, which affects the purity of the battery-grade lithium salt product, SO CO ₃ ^2- is removed by acidification first, Ca ²⁺, Mg ²⁺, Fe ³⁺ are removed by alkalization, and then mirabilite is precipitated by freezing method to remove most of Na ⁺ and SO ₄ ^2- , K ⁺ and Cl ^- are easily soluble in water and still exist in the solution after continuous circulation, which is difficult to remove, SO the conventional process can generally recover industrial-grade lithium salt from the sodium precipitation mother liquor.

in order to make the technical solutions of the present application more clearly understood by those skilled in the art, the following detailed description is given with reference to specific embodiments. If the experimental conditions not specified in the examples are specified, the conditions are generally conventional or recommended by the reagent company; reagents, consumables, and the like used in the following examples are commercially available unless otherwise specified.