阅读说明：本技术 一种从氧化铝生产过程提取锂并制备电池级碳酸锂的方法 (Method for extracting lithium and preparing battery-grade lithium carbonate from alumina production process ) 是由 韩东战 齐利娟 宋二伟 武国宝 于 2019-10-28 设计创作，主要内容包括：本发明涉及一种从氧化铝生产过程提取锂并制备电池级碳酸锂的方法：将精液降温后与酸性化合物反应制备氢氧化铝活性晶种；再将活性晶种与铝酸钠溶液混合,富集铝酸钠溶液中的锂,得到富锂氢氧化铝；将富锂氢氧化铝与有机酸混合进行微波脱附反应,反应结束后进行固液分离,固体为脱锂氢氧化铝,液体为富锂脱附液；富锂脱附液中加入碱液调整pH值,并加入锂净化抑制剂,脱除铝离子、铁离子、钙离子、镁离子得富锂精制液；在富锂精制液中加饱和碳酸钠溶液沉锂,得碳酸锂粗品,用高纯水反复洗涤得电池级碳酸锂。本发明实现了氧化铝生产流程中锂的高效高质提取,而且与现有氧化铝生产流程无缝对接,工艺简单、生产成本低,适宜产业化推广。(The invention relates to a method for extracting lithium and preparing battery-grade lithium carbonate from an alumina production process, which comprises the following steps: cooling the refined solution, and reacting the cooled refined solution with an acidic compound to prepare an aluminum hydroxide active seed crystal; mixing the active crystal seeds with the sodium aluminate solution to enrich lithium in the sodium aluminate solution to obtain lithium-rich aluminum hydroxide; mixing lithium-rich aluminum hydroxide and organic acid for microwave desorption reaction, and performing solid-liquid separation after the reaction is finished, wherein the solid is lithium-removed aluminum hydroxide, and the liquid is lithium-rich desorption liquid; adding alkali liquor into the lithium-rich desorption solution to adjust the pH value, adding a lithium purification inhibitor, and removing aluminum ions, iron ions, calcium ions and magnesium ions to obtain a lithium-rich refined solution; and adding a saturated sodium carbonate solution into the lithium-rich refined solution to precipitate lithium to obtain a crude lithium carbonate product, and repeatedly washing with high-purity water to obtain the battery-grade lithium carbonate. The invention realizes the high-efficiency and high-quality extraction of lithium in the production flow of the aluminum oxide, is in seamless butt joint with the existing production flow of the aluminum oxide, has simple process and low production cost, and is suitable for industrialized popularization.)

1. A method of extracting lithium from an alumina production process and preparing battery grade lithium carbonate, the method comprising the steps of:

(1) preparing active seed crystal: cooling the refined solution and then reacting the cooled refined solution with an acidic compound to obtain an aluminum hydroxide active seed crystal;

(2) and (3) enriching lithium: carrying out agglomeration reaction on the aluminum hydroxide active seed crystal prepared in the step (1) and a sodium aluminate solution to enrich lithium in the sodium aluminate solution to obtain material slurry, carrying out solid-liquid separation on the material slurry, wherein the solid is lithium-enriched aluminum hydroxide, and the liquid phase returns to a decomposition process to continue decomposition;

(3) microwave desorption: washing the lithium-rich aluminum hydroxide obtained in the step (2) with water, mixing the washed lithium-rich aluminum hydroxide with organic acid to prepare slurry, placing the slurry in a microwave reactor for lithium desorption reaction, and performing solid-liquid separation after the reaction is finished, wherein the solid is lithium-removed aluminum hydroxide, and the liquid is lithium-rich desorption liquid;

(4) solution purification: adding alkali liquor into the lithium-rich desorption solution obtained in the step (3) to adjust the pH value, and adding a lithium purification inhibitor to remove aluminum ions; performing solid-liquid separation, adding alkali liquor into the filtrate after the solid-liquid separation to adjust the pH value of the solution, removing calcium ions, magnesium ions and iron ions in the filtrate, performing solid-liquid separation after the reaction is finished, wherein the filtrate is a lithium-rich refined solution, and returning the solid to the step (1) to be used as an aluminum hydroxide active seed crystal;

(5) and (3) lithium deposition: and (4) concentrating the lithium-rich refined solution obtained in the step (4), adding a saturated sodium carbonate solution to precipitate lithium to obtain a crude lithium carbonate product, and repeatedly washing the crude lithium carbonate product with high-purity water to obtain battery-grade lithium carbonate with the purity of more than 99.5%.

2. The method for extracting lithium and preparing battery grade lithium carbonate from an alumina production process according to claim 1, wherein the sodium aluminate solution concentration range of step (2) is: na (Na)₂O_k：100g/L～180g/L，Na₂O_c：5g/L～40g/L，α_k：1.10～2.2。

3. The method for extracting lithium from an alumina production process and preparing battery grade lithium carbonate according to claim 1, wherein the refined solution in the step (1) is subjected to a neutralization reaction with one of 0.5mol/L to 1.5mol/L of aluminum nitrate, 0.5mol/L to 1.5mol/L of aluminum sulfate or 0.5mol/L to 1.5mol/L of aluminum chloride to obtain active aluminum hydroxide seed crystals, and the conditions of the neutralization reaction are as follows: the reaction temperature is 30-70 ℃, the reaction time is 10-50 min, and the pH of the slurry after reaction is 8-10.

4. The method for extracting lithium and preparing battery grade lithium carbonate from alumina production process as claimed in claim 1, wherein the average particle size of the active aluminum hydroxide seed crystals obtained in step (1) is 0.5 μm to 2.0 μm.

5. The process for extracting lithium from an alumina production process and preparing battery grade lithium carbonate according to claim 1, wherein the conditions for enriching lithium in the sodium aluminate solution in step (2) are as follows: the reaction time is 180 min-300 min, the reaction temperature is 70-80 ℃, and the adding amount of the aluminum hydroxide active seed crystal is 0.1 g/L-1.0 g/L.

6. The method for extracting lithium and preparing battery grade lithium carbonate from an alumina production process according to claim 1, wherein the aluminum hydroxide active seed crystals in the step (2) are enriched for 3-5 times in a circulating way; the lithium content in the lithium-rich aluminum hydroxide obtained in the step (2) is 0.5-2.0%.

7. The method for extracting lithium and preparing battery grade lithium carbonate from alumina production process according to claim 1, wherein the frequency of the microwave reactor in step (3) is 100 MHz-100 GHz; adding organic acid into the microwave reactor in the step (3) to perform desorption reaction of lithium on the slurry, wherein the desorption reaction conditions are as follows: the concentration of the organic acid is 0.1-1.0 mol/L, the reaction time is 5-60 min, the reaction temperature is 50-105 ℃, and the liquid-solid ratio of the organic acid to the lithium-rich aluminum hydroxide is 1-10; the organic acid is one of formic acid, acetic acid, propionic acid, butyric acid and valeric acid; the delithiated aluminum hydroxide obtained in the step (3) is easily soluble aluminum hydroxide and is a production raw material of polyaluminium chloride and aluminum sulfate.

8. The method for extracting lithium and preparing battery-grade lithium carbonate from an aluminum oxide production process according to claim 1, wherein in the step (4), alkali liquor is added into the lithium-rich desorption solution to adjust the pH value to 2.5-5.0, and then a lithium purification inhibitor is added, wherein the conditions for removing aluminum ions are as follows: the reaction temperature is 30-100 ℃, and the reaction time is 30-300 min; the lithium purification inhibitor is one of ammonium sulfate, ammonium chloride and ammonium phosphate, and the molar ratio of the lithium purification inhibitor to lithium ions in the lithium-rich desorption solution is 0.01-0.1.

9. The method for extracting lithium and preparing battery-grade lithium carbonate from an aluminum oxide production process according to claim 1, wherein after aluminum ions are removed from the lithium-rich desorption solution in the step (4) and solid-liquid separation is carried out, 1.0 mol/L-8.0 mol/L sodium hydroxide solution is added into the obtained filtrate to adjust the pH value of the solution to 9-13, calcium ions, magnesium ions and iron ions in the filtrate are removed, the reaction time for removing the calcium ions, the magnesium ions and the iron ions in the filtrate is 20 min-200 min, and the reaction temperature is 20 ℃ to 90 ℃.

10. The method for extracting lithium and preparing battery-grade lithium carbonate from an alumina production process according to claim 1, wherein the concentration of lithium in the lithium-rich refined solution after concentration in step (5) is 15g/L to 30 g/L; when the lithium-rich refined solution is concentrated and then added with a saturated sodium carbonate solution for precipitating lithium in the step (5), the adding amount of the sodium carbonate is 105-130% of the molar equivalent of lithium in the lithium-rich refined solution, and the lithium precipitation temperature is 70-95 ℃; the mass ratio of the lithium carbonate crude product to the high-purity water in the step (5) is 1 (3-5).

Technical Field

The invention belongs to the field of lithium salt preparation, and particularly relates to a method for extracting lithium from an alumina production process and preparing battery-grade lithium carbonate.

Background

Lithium carbonate is the basic material for the production of secondary lithium salts and metallic lithium and, therefore, is also the most basic and important product in the lithium industry. Can not only be directly used as a product, but also be used for producing lithium alloy and lithium compounds. Lithium carbonate is widely applied to a plurality of fields of electronic materials, chemistry, medical treatment, industrial ceramics, metallurgy and the like. With the rapid development of high and new technology industries such as information technology, electric vehicles, green energy and the like, the market demand of lithium and compounds thereof is increased day by day, the demand is short, and the price is high. The domestic high-quality lithium ore resources are deficient, the separation of magnesium and lithium from high-magnesium brine in a salt lake is difficult in China, the huge capacity increase of the foreign lithium industry is limited, so that the supply is insufficient, and the lithium resources in minerals and brine are difficult to meet the sustainable development requirements of human beings in the long run.

Bauxite resources are rich in middle regions of China, the bauxite in the regions is rich in lithium elements, in the production process of alumina by a Bayer process, about 80% of lithium enters a solution in the digestion process of the Bayer process (Caoalin, Lichun, "research on lithium enrichment mechanism in the production process of alumina by the Bayer process" "No. 9 in 2017 in nonferrous metals (smelting part), P23-26) and finally enters an alumina product, so that the alumina produced by taking the bauxite as a raw material has high lithium content (Li in the alumina product in 2017 by an alumina enterprise in Henan, and the like)₂O0.14%). The alumina is a raw material for aluminum electrolysis, and the long-term use of the alumina with high lithium content can cause serious influence on the aluminum electrolysis process, such as reduction of electrolysis temperature, deterioration of furnace regularity, reduction of electrolysis production stability, reduction of current efficiency, increase of energy consumption and the like. Li in alumina factory products in middle area of China₂O is generally higher if the alumina Li₂O content was estimated as 0.1%, alumina production was estimated as 1200 million tons/year, Li taken from metallurgical grade alumina per year₂O is as high as 12000 tons, and the lithium resources are not reasonably utilized.

The lithium resource in the alumina production flow in the middle area is rich, and the extraction of the lithium resource in the alumina production flow is not only beneficial to improving the quality of alumina products and eliminating the adverse effect on downstream aluminum electrolysis, but also beneficial to supplement the lithium resource in China, so researchers develop the research on recovering lithium from the alumina flow. The patent "method of extracting lithium carbonate from sodium aluminate solution in alumina plant" (CN 107500318B) discloses a method of preparing lithium carbonate from lithium-containing sodium aluminate solution, the method firstly adds aluminum hydroxide into lithium-containing sodium aluminate solution to absorb lithium to obtain primary high-lithium aluminum hydroxide, re-dissolves the primary high-lithium aluminum hydroxide with evaporation mother liquor to obtain high-lithium refined solution, adds aluminum hydroxide seed crystal into the high-lithium refined solution to obtain secondary high-lithium aluminum hydroxide, adopts hydrothermal leaching method to treat secondary high-lithium aluminum hydroxide to obtain lithium-containing leachate, adds inorganic acid such as hydrochloric acid and the like into the lithium-containing leachate to neutralize, filters and separates the generated aluminum glue to obtain lithium salt solution, evaporates and concentrates the lithium salt solution until the lithium content is more than 30g/L, then adds sodium carbonate solution to precipitate lithium, filters, washes and dries to obtain lithium carbonate product with purity of more than 90%, the recovery rate of lithium is more than 70%. The method has the advantages that the process flow is complex, the indexes of the aluminum hydroxide seed crystals lack specific requirements, the aluminum hydroxide with thicker granularity is used as the seeds, the agglomeration reaction is difficult to occur, and the lithium removal effect is not ideal; moreover, lithium completely enters the aluminum hydroxide, more aluminum hydroxide can be decomposed, the content of lithium in the aluminum hydroxide is low, and the purpose of high-efficiency enrichment cannot be achieved; in addition, the leaching rate of hydrothermal phase inversion lithium is low, the process is complex, the energy consumption is high, the comprehensive recovery rate of lithium is low, and the aim that the recovery rate of lithium is more than 70 percent is difficult to realize.

The patent "method and system for resolving lithium in lithium-rich adsorbent in alumina factory" (CN 109761249A) adopts adsorption method to extract lithium-rich adsorbent generated by lithium in sodium aluminate solution, further adopts the principle of high-temperature high-pressure hydrothermal leaching to resolve lithium, a hydrothermal reaction unit adopts the full-pipeline slurry and slurry heat exchange technology, the reaction temperature of hydrothermal resolution is 160-220 ℃, the reaction time is 0.5-2 h, L/S is 5-30, through multiple countercurrent resolution process, the content of lithium in resolution solution is more than 0.5g/L, the resolution rate of lithium in adsorbent is more than or equal to 90%, the energy consumption of hydrothermal treatment process is high, especially pipeline treatment scabbingSevere and costly to clean. The invention discloses a method and a system for purifying lithium-containing analytic solution in a concentrated alumina plant (CN 109650416A). the method adopts acid-base neutralization and membrane separation to purify and concentrate the lithium-containing analytic solution, the lithium recovery rate is more than or equal to 90 percent, and Li in the concentrated solution is more than or equal to 90 percent⁺Not less than 8 g/L. The patent "method and system for enriching lithium from sodium aluminate solution in alumina plant" (CN 109650413A) proposes a method for enriching lithium by adding aluminum hydroxide adsorbent in sodium aluminate solution in plant, and the lithium content in the obtained aluminum-based lithium-enriched slag is 4.0-6.0%. The partial redissolution method is used for enriching lithium, although high-lithium aluminum hydroxide can be partially dissolved, the purpose of enriching lithium is achieved to a certain extent, because lithium coexists in an intercalated form in the aluminum hydroxide crystal structure, the partial dissolution degree of aluminum hydroxide is difficult to control, the high-efficiency dissolution of lithium cannot be ensured, and the process energy consumption is high.

The industrial processes for preparing lithium salts are mainly divided into two categories:

one is that the lithium in the brine is enriched by comprehensively extracting and utilizing the minerals of other valuable metals in the brine from the brine containing the lithium, and finally the Li can be obtained₂CO₃Or Li₂SO₄·H₂O and other lithium salt products, but because most domestic salt lake brine has the characteristic of low magnesium-lithium ratio, the development difficulty is high, and the industrial implementation of extracting lithium from the brine is difficult; another method is to destroy the original gangue structure of the main lithium-containing ores, spodumene and lepidolite, by pyrogenic or wet treatment of the ore to destroy the original gangue structure and to make Li in the ore₂O is dissolved in the form of a soluble lithium salt, such as Li₂SO₄And other forms of lithium salts. The process for extracting lithium salt from spodumene has the advantages of small material flow, high production efficiency, low energy consumption, high lithium recovery rate and the like, so that the method for extracting lithium by taking spodumene as a raw material is a widely adopted method at present.

The existing methods for extracting lithium by utilizing spodumene mainly comprise a sulfuric acid method and a lime method, and the lime method is less adopted due to the defects of high energy consumption, low recovery rate, high production cost and the like. The sulfuric acid method consumes a large amount of sulfuric acid, and has the defects of long industrial process, high requirement on equipment, environmental pollution and the like.

The battery-grade lithium carbonate has strict requirements on sulfate radicals and chloride ions, and the inorganic acid is adopted to treat the lithium-rich material, so that the environmental pollution is caused to the environment, the cost of the removal process of the sulfate radicals and the chloride ions is high, if excessive barium chloride is required to be added to remove the sulfate radicals to generate barium sulfate precipitates, the excessive barium ions are required to be removed by adding excessive sodium carbonate to generate barium carbonate precipitates, and the removal of the sulfate ions by a barium salt method is high in cost and involves the use of a virulent medicament barium chloride, so that the potential safety hazard exists.

Disclosure of Invention

The invention provides a method for extracting lithium and preparing battery-grade lithium carbonate from an alumina production process, aiming at solving the problems of long lithium recovery process flow, low recovery rate, high cost and the like in the prior art, providing a feasible method for producing battery-grade lithium carbonate by an alumina enterprise using high-lithium bauxite as a raw material and opening up a new technical route for efficiently recovering valuable metals in bauxite with complex components.

In order to solve the technical problems, the invention adopts the following technical scheme:

a method of extracting lithium from an alumina production process and preparing battery grade lithium carbonate, the method comprising the steps of:

(1) preparing active seed crystal: cooling the refined solution and then reacting the cooled refined solution with an acidic compound to obtain an aluminum hydroxide active seed crystal;

(2) and (3) enriching lithium: carrying out agglomeration reaction on the aluminum hydroxide active seed crystal prepared in the step (1) and a sodium aluminate solution to enrich lithium in the sodium aluminate solution to obtain material slurry, carrying out solid-liquid separation on the material slurry, wherein the solid is lithium-enriched aluminum hydroxide, and the liquid phase returns to a decomposition process to continue decomposition;

(3) microwave desorption: washing the lithium-rich aluminum hydroxide obtained in the step (2) with water, mixing the washed lithium-rich aluminum hydroxide with organic acid to prepare slurry, placing the slurry in a microwave reactor for lithium desorption reaction, and performing solid-liquid separation after the reaction is finished, wherein the solid is lithium-removed aluminum hydroxide, and the liquid is lithium-rich desorption liquid;

(4) solution purification: adding alkali liquor into the lithium-rich desorption solution obtained in the step (3) to adjust the pH value, and adding a lithium purification inhibitor to remove aluminum ions; performing solid-liquid separation, adding alkali liquor into the filtrate after the solid-liquid separation to adjust the pH value of the solution, removing calcium ions, magnesium ions and iron ions in the filtrate, performing solid-liquid separation after the reaction is finished, wherein the filtrate is a lithium-rich refined solution, and returning the solid to the step (1) to be used as an aluminum hydroxide active seed crystal;

(5) and (3) lithium deposition: and (4) concentrating the lithium-rich refined solution obtained in the step (4), adding a saturated sodium carbonate solution to precipitate lithium to obtain a crude lithium carbonate product, and repeatedly washing the crude lithium carbonate product with high-purity water to obtain battery-grade lithium carbonate with the purity of more than 99.5%.

The method for extracting lithium and preparing battery-grade lithium carbonate from the alumina production process, which is characterized in that the concentration range of the sodium aluminate solution in the step (2) is as follows: na (Na)₂O_k：100g/L～180g/L，Na₂O_c：5g/L～40g/L，α_k：1.10～2.2。

The method for extracting lithium and preparing battery-grade lithium carbonate from the alumina production process is characterized in that in the step (1), the refined solution is subjected to neutralization reaction with one of 0.5-1.5 mol/L aluminum nitrate, 0.5-1.5 mol/L aluminum sulfate or 0.5-1.5 mol/L aluminum chloride to obtain active aluminum hydroxide seed crystals, and the conditions of the neutralization reaction are as follows: the reaction temperature is 30-70 ℃, the reaction time is 10-50 min, and the pH of the slurry after reaction is 8-10.

The method for extracting lithium from the alumina production process and preparing battery grade lithium carbonate is characterized in that the average particle size of the active aluminum hydroxide seed crystals obtained in the step (1) is 0.5-2.0 μm.

The method for extracting lithium from the alumina production process and preparing battery-grade lithium carbonate is characterized in that the conditions for enriching lithium in the sodium aluminate solution in the step (2) are as follows: the reaction time is 180 min-300 min, the reaction temperature is 70-80 ℃, and the adding amount of the aluminum hydroxide active seed crystal is 0.1 g/L-1.0 g/L.

The method for extracting lithium and preparing battery-grade lithium carbonate from the production process of aluminum oxide is characterized in that the active aluminum hydroxide crystal seeds in the step (2) are subjected to cyclic enrichment for 3-5 times; the lithium content in the lithium-rich aluminum hydroxide obtained in the step (2) is 0.5-2.0%.

The method for extracting lithium and preparing battery-grade lithium carbonate from the alumina production process is characterized in that the frequency of the microwave reactor in the step (3) is 100 MHz-100 GHz; adding organic acid into the microwave reactor in the step (3) to perform desorption reaction of lithium on the slurry, wherein the desorption reaction conditions are as follows: the concentration of the organic acid is 0.1-1.0 mol/L, the reaction time is 5-60 min, the reaction temperature is 50-105 ℃, and the liquid-solid ratio of the organic acid to the lithium-rich aluminum hydroxide is 1-10; the organic acid is one of formic acid, acetic acid, propionic acid, butyric acid and valeric acid; the delithiated aluminum hydroxide obtained in the step (3) is easily soluble aluminum hydroxide and is a production raw material of polyaluminium chloride and aluminum sulfate.

The method for extracting lithium and preparing battery-grade lithium carbonate from the production process of aluminum oxide is characterized in that alkali liquor is added into the lithium-rich desorption solution in the step (4) to adjust the pH value to 2.5-5.0, then a lithium purification inhibitor is added, and the conditions for removing aluminum ions are as follows: the reaction temperature is 30-100 ℃, and the reaction time is 30-300 min; the lithium purification inhibitor is one of ammonium sulfate, ammonium chloride and ammonium phosphate, and the molar ratio of the lithium purification inhibitor to lithium ions in the lithium-rich desorption solution is 0.01-0.1.

The method for extracting lithium and preparing battery-grade lithium carbonate from the production process of aluminum oxide is characterized in that after aluminum ions are removed from the lithium-rich desorption solution in the step (4) and solid-liquid separation is carried out, 1.0-8.0 mol/L sodium hydroxide solution is added into the obtained filtrate to adjust the pH value of the solution to 9-13, calcium ions, magnesium ions and iron ions in the filtrate are removed, the reaction time for removing the calcium ions, the magnesium ions and the iron ions in the filtrate is 20-200 min, and the reaction temperature is 20-90 ℃.

The method for extracting lithium and preparing battery-grade lithium carbonate from the alumina production process is characterized in that the concentration of lithium in the lithium-rich refined solution concentrated in the step (5) is 15 g/L-30 g/L; when the lithium-rich refined solution is concentrated and then added with a saturated sodium carbonate solution for precipitating lithium in the step (5), the adding amount of the sodium carbonate is 105-130% of the molar equivalent of lithium in the lithium-rich refined solution, and the lithium precipitation temperature is 70-95 ℃; the mass ratio of the lithium carbonate crude product to the high-purity water in the step (5) is 1 (3-5).

The invention has the beneficial technical effects that:

1. the high-activity aluminum hydroxide crystal seeds are added into the sodium aluminate solution to enrich lithium, the high-activity crystal seeds with certain granularity requirement are subjected to agglomeration reaction in the sodium aluminate solution, the agglomeration reaction can ensure that the extraction rate of lithium is greatly improved, the decomposition rate of the sodium aluminate solution is controlled to be less than 2.0 percent, the lithium content in lithium-rich aluminum hydroxide can be greatly improved, and the adding amount of the active crystal seeds is 10 to 20 percent of the using amount of the conventional crystal seeds.

2. The method carries out the desorption reaction of lithium in a microwave reactor, and realizes the purpose of efficiently desorbing the lithium in the lithium-rich aluminum hydroxide in shorter time by determining the liquid-solid ratio of reaction slurry, the reaction temperature and the reaction time.

3. The delithiated aluminum hydroxide obtained in the implementation process of the method is a new product with high added value, namely easily soluble aluminum hydroxide, and is mainly used for aluminum salt production.

4. When the lithium purification preparation is used for efficiently removing impurities in a high-lithium solution, the loss rate of lithium is very low, the removal rate of Fe, Ca, Mg and Al in a lithium-rich desorption solution is more than 99.0%, and the loss rate of lithium is less than 1.0%.

5. Compared with the prior art, the method has the advantages of simple process flow, low cost, seamless connection between the extraction process and the alumina production flow, low investment and suitability for popularization and application in alumina production enterprises by using high-lithium bauxite. The purity of the battery-grade lithium carbonate obtained by the method is more than 95.5 percent, and the recovery rate of lithium is more than 85 percent.

Drawings

FIG. 1 is a process flow diagram of the present invention.

Detailed Description

Referring to fig. 1, a method of the present invention for extracting lithium and producing battery grade lithium carbonate from an alumina production process includes the steps of: (1) preparing active seed crystal: cooling the refined liquid, and reacting the cooled refined liquid with an acidic compound by utilizing an acid-base neutralization principle to obtain an aluminum hydroxide active seed crystal; preferably, the refined solution and one of 0.5 mol/L-1.5 mol/L of aluminum nitrate, 0.5 mol/L-1.5 mol/L of aluminum sulfate or 0.5 mol/L-1.5 mol/L of aluminum chloride are subjected to neutralization reaction to prepare the active aluminum hydroxide seed crystal, and the conditions of the neutralization reaction are as follows: the reaction temperature is 30-70 ℃, the reaction time is 10-50 min, and the pH of the slurry after reaction is 8-10. The average grain diameter of the aluminum hydroxide active seed crystal is 0.5-2.0 μm. (2) And (3) enriching lithium: carrying out agglomeration reaction on the aluminum hydroxide active seed crystal prepared in the step (1) and a sodium aluminate solution to enrich lithium in the sodium aluminate solution to obtain material slurry, and circularly enriching the aluminum hydroxide active seed crystal for 3-5 times; and (3) performing solid-liquid separation on the material slurry, wherein the solid is lithium-rich aluminum hydroxide, and the lithium content in the obtained lithium-rich aluminum hydroxide is 0.5-2.0%. The liquid phase returns to the decomposition process to continue decomposition; the concentration range of the sodium aluminate solution is as follows: na (Na)₂O_k：100g/L～180g/L，Na₂O_c：5g/L～40g/L，α_k: 1.10 to 2.2. The conditions for enriching lithium in the sodium aluminate solution are as follows: the reaction time is 180 min-300 min, the reaction temperature is 70-80 ℃, and the adding amount of the aluminum hydroxide active seed crystal is 0.1 g/L-1.0 g/L. (3) Microwave desorption: washing the lithium-rich aluminum hydroxide obtained in the step (2) with water, mixing the washed lithium-rich aluminum hydroxide with organic acid to prepare slurry, placing the slurry in a microwave reactor for lithium desorption reaction, and performing solid-liquid separation after the reaction is finished, wherein the solid is lithium-removed aluminum hydroxide, and the liquid is lithium-rich desorption liquid; the frequency of the microwave reactor is 100 MHz-100 GHz; adding organic acid into the microwave reactor in the step (3) to carry out desorption reaction of lithium on the slurry, wherein the desorption reaction conditions are as follows: the concentration of the organic acid is 0.1-1.0 mol/L, the reaction time is 5-60 min, the reaction temperature is 50-105 ℃, and the liquid-solid ratio of the organic acid to the lithium-rich aluminum hydroxide is 1-E10; the organic acid is one of formic acid, acetic acid, propionic acid, butyric acid and valeric acid; the delithiated aluminum hydroxide obtained in the step (3) is easily soluble aluminum hydroxide and can be used as a production raw material of polyaluminium chloride and aluminum sulfate. (4) Solution purification: adding alkali liquor into the lithium-rich desorption solution obtained in the step (3) to adjust the pH value, and adding a lithium purification inhibitor to remove aluminum ions; performing solid-liquid separation, adding alkali liquor into the filtrate after the solid-liquid separation to adjust the pH value of the solution, removing Fe, Ca, Mg and other ions in the filtrate, performing solid-liquid separation after the reaction is finished, wherein the filtrate is a lithium-rich refined solution, and returning the solid to the step (1) to be used as an aluminum hydroxide active seed crystal; adding alkali liquor into the lithium-rich desorption solution in the step (4) to adjust the pH value to 2.5-5.0, adding a lithium purification inhibitor, and removing aluminum ions under the conditions that: the reaction temperature is 30-100 ℃, and the reaction time is 30-300 min; the lithium purification inhibitor is one of ammonium sulfate, ammonium chloride and ammonium phosphate, and the molar ratio of the lithium purification inhibitor to lithium ions in the lithium-rich desorption solution is 0.01-0.1. Removing aluminum ions from the lithium-rich desorption solution in the step (4), performing solid-liquid separation, adding 1.0-8.0 mol/L sodium hydroxide solution into the obtained filtrate, adjusting the pH value of the solution to 9-13, removing calcium ions, magnesium ions and iron ions from the filtrate, wherein the reaction time for removing the calcium ions, the magnesium ions and the iron ions from the filtrate is 20-200 min, and the reaction temperature is 20-90 ℃. (5) And (3) lithium deposition: and (4) concentrating the lithium-rich refined solution obtained in the step (4), adding a saturated sodium carbonate solution to precipitate lithium to obtain a crude lithium carbonate product, and repeatedly washing the crude lithium carbonate product with high-purity water to obtain battery-grade lithium carbonate with the purity of more than 99.5%. The concentration of lithium in the lithium-rich refined solution concentrated in the step (5) is 15 g/L-30 g/L; when the lithium-rich refined solution is concentrated and then added with a saturated sodium carbonate solution for precipitating lithium in the step (5), the adding amount of the sodium carbonate is 105-130% of the molar equivalent of lithium in the lithium-rich refined solution, and the lithium precipitation temperature is 70-95 ℃; the mass ratio of the lithium carbonate crude product to the high-purity water in the step (5) is 1 (3-5).

To further illustrate the essence of the present invention, the following examples are given by way of illustration only, and should not be construed to limit the scope of the present invention: