Method for recovering and preparing lithium carbonate from calcined ash of waste lithium battery

Abstract

The invention provides a method for recycling and preparing lithium carbonate from waste lithium battery calcination ash, the process is simple, the recycling efficiency is high, lithium is recycled from the waste lithium battery calcination ash, and lithium carbonate and crude lithium carbonate with the purity larger than 99.5% are prepared, and the method comprises the following steps that the calcined ash is dissolved with pure water under the ultrasonic condition; the method comprises the following steps: dissolving a lithium carbonate solution, introducing carbon dioxide while dissolving to obtain a lithium bicarbonate solution, carrying out ultrafiltration impurity removal and reverse osmosis concentration on a leaching solution to improve the lithium concentration, and carrying out reduced-pressure pyrolysis to obtain lithium carbonate with the purity of more than 99.5%, so that high-purity lithium carbonate can be simply and conveniently obtained, and meanwhile, residual lithium resources are used for preparing crude lithium carbonate to reduce the loss of lithium; in the ash dissolving process, acid is not adopted, only pure water and carbon dioxide are adopted, main cations in the solution are lithium ions, other metal ions are hardly dissolved, other noble metals can be continuously extracted from residual solid residues, and other noble metals in the battery ash are not lost in the lithium extraction process.

Description

Technical Field

[0001] The invention belongs to the technical field of lithium battery recycling, and specifically relates to a method for recovering and preparing lithium carbonate from calcined ash of waste lithium batteries. Background Art

[0002] According to statistics from the Ministry of Industry and Information Technology, my country's new energy vehicle sales will reach 6 million in 2022. According to the 5-8 years of service life of passenger vehicle batteries, more and more lithium batteries will be retired in the future. Recycling lithium metal from waste batteries will be an important way to solve my country's lithium energy shortage.

[0003] Among them, calcining the battery at high temperature and then dissolving and extracting lithium is an important method for recovering lithium. The existing recovery method is to discharge the waste lithium battery, calcine it in a high-temperature furnace, and extract the ash after calcination with inorganic acid or organic acid to recover lithium. Due to the introduction of acid, other metal ions in the ash will be dissolved, resulting in the loss of other metal ions in the battery during the lithium extraction process. At the same time, the dissolution of other metals increases the difficulty of subsequent lithium extraction. There is also a method of using pure water to dissolve the ash after battery calcination, but there is a problem of poor lithium solubility, resulting in a low lithium recovery rate.

[0004] Based on this, a method for recovering and preparing lithium carbonate from the calcined ash of waste lithium batteries is proposed. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for recovering and preparing lithium carbonate from the calcined ash of waste lithium batteries in view of the shortcomings of the above-mentioned prior art, so as to solve the problems raised in the above-mentioned background technology.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for recovering and preparing lithium carbonate from calcined ash of waste lithium batteries, comprising the following steps:

[0007] S1. Ultrasonic leaching with pure water: The ash after calcination of waste lithium batteries is leached with pure water under ultrasonic conditions, and carbon dioxide is introduced during leaching to convert lithium carbonate into lithium bicarbonate, thereby increasing the concentration of lithium in the solution;

[0008] S2. Solid-liquid separation of the leaching liquid: The leaching liquid is separated into solid and liquid by a centrifuge to obtain a liquid phase and a solid phase residue, and the solid phase residue can be used to recover other metals later;

[0009] S3, ultrafiltration purification: The obtained liquid phase is subjected to ultrafiltration pretreatment using a tubular membrane to remove particulate impurities in the solution, and the divalent and above cations in the tubular membrane produced water are removed using a cationic resin to obtain a purified liquid after impurities are removed;

[0010] S4, reverse osmosis concentration: the purified liquid after impurity removal by resin is subjected to reverse osmosis concentration to increase the concentration of lithium in the solution until lithium bicarbonate is close to saturation, and the reverse osmosis concentrated liquid is subjected to low-temperature pyrolysis to prepare lithium carbonate, while the by-product reverse osmosis fresh water is returned to the pure water leaching step to reduce the amount of pure water used;

[0011] S5, decomposition liquid solid-liquid separation: the mother liquor after pyrolysis and the lithium carbonate solid phase are centrifuged and separated by a centrifuge;

[0012] S6. Preparation of high-purity lithium carbonate by freeze crystallization: freeze-dry the separated solid lithium carbonate in a freeze dryer to remove moisture and obtain high-purity lithium carbonate; the lithium-containing mother liquor after solid-liquid separation is divided into two parts, one part of which is decarbonized in order to improve the recovery rate of lithium, and then circulated back to the front-end ultrafiltration purification step; because impurity ions will be enriched during the circulation process, resulting in a decrease in the purity of lithium, the other part of the mother liquor leaves the battery-grade lithium carbonate preparation process and is used to prepare crude lithium carbonate after decarbonization;

[0013] S7, carbon removal: sulfuric acid is added to the lithium precipitation mother liquor after solid-liquid separation, and sulfuric acid reacts with lithium carbonate and lithium bicarbonate to form lithium sulfate, and the solution after carbon removal is evaporated and concentrated;

[0014] S8. Lithium precipitation: Sodium carbonate is added to the concentrated solution to precipitate solid lithium carbonate. The mother liquor and the lithium carbonate solid phase after lithium precipitation are centrifuged and separated. The solid lithium carbonate is dehydrated and dried to obtain crude lithium carbonate. The solution after solid-liquid separation is discharged from the system.

[0015] As a further illustration of the present invention, the water-cement mass ratio in S1 is 20:1-40:1, and the pH value of the solution is 6-9 after the introduction of carbon dioxide.

[0016] As a further illustration of the present invention, the operating pressure of the tubular membrane in S3 is 0.05-0.2 MPa.

[0017] As a further illustration of the present invention, the lithium ion concentration of the reverse osmosis concentrate in S4 is 6-7.5 g / L.

[0018] As a further illustration of the present invention, the pyrolysis temperature in S4 is 70-90°C.

[0019] As a further illustration of the present invention, the purity of lithium carbonate in S6 is greater than 99.5%.

[0020] As a further illustration of the present invention, the lithium ion concentration of the concentrated solution in S7 is 25-32 g / L.

[0021] Compared with the prior art, the present invention has the following advantages:

[0022] 1. The method of the present invention has simple process and high recovery efficiency. Lithium is recovered from the calcined ash of waste lithium batteries and lithium carbonate and crude lithium carbonate with a purity greater than 99.5% are prepared. The calcined ash is dissolved with pure water under ultrasonic conditions, and carbon dioxide is introduced while dissolving to obtain a lithium bicarbonate solution. The leached solution is subjected to ultrafiltration to remove impurities and reverse osmosis to increase the lithium concentration, and then decompressed pyrolysis is performed to obtain lithium carbonate with a purity greater than 99.5%. High-purity lithium carbonate can be obtained simply, and crude lithium carbonate is prepared from the remaining lithium resources to reduce lithium loss. Due to the ash dissolution process, no acid is used, only pure water and carbon dioxide are used, the main cations in the solution are lithium ions, and other metal ions are almost insoluble. The remaining solid slag can continue to be used to extract other precious metals, and other precious metals in the battery ash are not lost during the lithium extraction process.

[0023] 2. The present invention has the advantages of high lithium recovery rate, small loss of other metal elements, environmental friendliness, high product purity, etc., and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the overall method of the present invention. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0026] like Figure 1 As shown, the present invention provides a technical solution: a method for recovering and preparing lithium carbonate from calcined ash of waste lithium batteries, comprising the following steps:

[0027] S1. Ultrasonic leaching with pure water: The ash after calcination of waste lithium batteries is leached with pure water under ultrasonic conditions, and carbon dioxide is introduced during leaching to convert lithium carbonate into lithium bicarbonate to increase the concentration of lithium in the solution; the water-ash mass ratio is 20:1-40:1, and the pH of the solution is 6-9 after the introduction of carbon dioxide;

[0028] S2. Solid-liquid separation of the leached liquid: The leached solution and the solid phase are separated by a centrifuge to obtain a liquid phase;

[0029] S3, ultrafiltration purification: The obtained liquid phase is subjected to ultrafiltration pretreatment using a tubular membrane to remove particulate impurities in the solution, and the divalent and above cations in the tubular membrane produced water are removed using a cationic resin to obtain a purified liquid after impurities are removed. The operating pressure of the tubular membrane is 0.05-0.2MPa;

[0030] S4, reverse osmosis concentration: the purified liquid after impurity removal by resin is subjected to reverse osmosis concentration, the lithium ion concentration of the reverse osmosis concentrated liquid is 6-7.5g / L, the lithium concentration in the solution is increased to lithium bicarbonate close to saturation, and the reverse osmosis concentrated liquid is subjected to low-temperature pyrolysis to prepare lithium carbonate, the pyrolysis temperature is 70-90°C;

[0031] S5, decomposition liquid solid-liquid separation: the mother liquor after pyrolysis and the lithium carbonate solid phase are centrifuged and separated by a centrifuge;

[0032] S6. Preparation of high-purity lithium carbonate by freeze crystallization: freeze-drying the separated solid lithium carbonate in a freeze dryer to remove water and obtain high-purity lithium carbonate with a purity of more than 99.5%;

[0033] S7, decarbonization: sulfuric acid is added to the lithium precipitation mother liquor after solid-liquid separation, and sulfuric acid reacts with lithium carbonate and lithium bicarbonate to form lithium sulfate. The solution after decarbonization is evaporated and concentrated, and the lithium ion concentration of the concentrated solution is 25-32g / L;

[0034] S8. Lithium precipitation: Sodium carbonate is added to the concentrated solution to precipitate solid lithium carbonate. The mother liquor and the lithium carbonate solid phase after lithium precipitation are centrifuged and separated. The solid lithium carbonate is dehydrated and dried to obtain crude lithium carbonate. The solution after solid-liquid separation is discharged from the system.

[0035] Example 1, a method for recovering and preparing lithium carbonate from calcined ash of waste lithium batteries, comprising the following steps:

[0036] Take 200g of calcined ash, the lithium concentration is 40.85mg / g, add 4000g of deionized water, and stir under ultrasonic conditions;

[0037] After 30 minutes, carbon dioxide was introduced, and the pH dropped to 6.34, and the introduction of carbon dioxide was stopped;

[0038] The leaching solution was filtered and centrifuged, and the single-line recovery rate of lithium in the leaching process was 95%, and the concentration of lithium in the filtrate was 2.03g / L; after ultrafiltration purification and resin impurity removal, the water recovery rate of the reverse osmosis (RO) concentration process was 72%, and the lithium concentration was increased to 7.25g / L;

[0039] The negative pressure pyrolysis temperature was controlled at 90°C, the pyrolysis process lasted 30 minutes, and the lithium bicarbonate pyrolysis rate was 93%;

[0040] Solid phase freeze drying was used to prepare high-purity lithium carbonate, and 29.57 g of high-purity lithium carbonate was obtained. The yield of high-purity lithium carbonate was 68% and the purity was 99.62%.

[0041] The concentration of lithium in the mother liquor after pyrolysis is 1.91g / L. The mother liquor is decarbonized to prepare crude lithium carbonate. The decarbonization process uses 20% sulfuric acid. The concentration of lithium after evaporation and concentration is 27g / L. Sodium carbonate is added at 85°C to prepare crude lithium carbonate.

[0042] The solid phase obtained after solid-liquid separation by a centrifuge was placed in an oven and dried at 100° C. to obtain 4.35 g of crude lithium carbonate.

[0043] The total lithium loss in the process is 22%.

[0044] Example 2, a method for recovering and preparing lithium carbonate from calcined ash of waste lithium batteries, comprising the following steps:

[0045] Take 200g of calcined ash with a lithium concentration of 40.85mg / g, add 8000g of deionized water, and stir under ultrasonic conditions;

[0046] After 30 minutes, carbon dioxide was introduced, and the pH dropped to 6.52, and the introduction of carbon dioxide was stopped;

[0047] The leaching solution was filtered and centrifuged, and the single-line recovery rate of lithium in the leaching process was 95.4%, and the concentration of lithium in the filtrate was 1.06g / L; after ultrafiltration purification and resin impurity removal, the water recovery rate of the reverse osmosis (RO) concentration process was 85%, and the lithium concentration was increased to 7.07g / L;

[0048] The negative pressure pyrolysis temperature was controlled at 90°C, the pyrolysis process took 30 minutes, and the pyrolysis rate of lithium bicarbonate was 93%. High-purity lithium carbonate was prepared by solid phase freeze drying to obtain 30.01 g of high-purity lithium carbonate, with a yield of 69% and a purity of 99.57%.

[0049] The concentration of lithium in the mother liquor after pyrolysis is 1.91 g / L, and the mother liquor is decarbonized to prepare crude lithium carbonate. The decarbonization process uses 20% sulfuric acid, and the concentration of lithium after evaporation and concentration is 27.5 g / L. Sodium carbonate is added at 85°C to prepare crude lithium carbonate;

[0050] The solid phase obtained after solid-liquid separation by a centrifuge was placed in an oven and dried at 100° C. to obtain 4.34 g of crude lithium carbonate.

[0051] The total lithium loss in the process is 21%.

[0052] Example 3, a method for recovering and preparing lithium carbonate from calcined ash of waste lithium batteries, comprising the following steps:

[0053] Take 200g of calcined ash with a lithium concentration of 40.85mg / g, add 6000g of deionized water, and stir under ultrasonic conditions;

[0054] After 30 minutes, carbon dioxide was introduced, and the pH dropped to 7.23, and the introduction of carbon dioxide was stopped;

[0055] The leaching solution was filtered and centrifuged, and the single-line recovery rate of lithium in the leaching process was 95.1%, and the concentration of lithium in the filtrate was 1.52g / L; after ultrafiltration purification and resin impurity removal, the water recovery rate of the reverse osmosis (RO) concentration process was 77%, and the lithium concentration was increased to 6.61g / L;

[0056] The negative pressure pyrolysis temperature was controlled at 90° C., the pyrolysis process took 30 minutes, and the pyrolysis rate of lithium bicarbonate was 93%. High-purity lithium carbonate was prepared by solid phase freeze drying to obtain 29.92 g of high-purity lithium carbonate, with a yield of 68.8% and a purity of 99.58%.

[0057] The concentration of lithium in the mother liquor after pyrolysis is 1.91 g / L, and the mother liquor is decarbonized to prepare crude lithium carbonate. The decarbonization process uses 20% sulfuric acid, and the concentration of lithium after evaporation and concentration is 27.5 g / L. Sodium carbonate is added at 85°C to prepare crude lithium carbonate;

[0058] The solid phase obtained after solid-liquid separation by a centrifuge was placed in an oven at 100° C. for drying to obtain 4.26 g of crude lithium carbonate.

[0059] The total lithium loss in the process is 21%.

[0060] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0061] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for recovering and preparing lithium carbonate from calcined ash of waste lithium batteries, characterized in that: The following steps are involved: S1. Ultrasonic leaching with pure water: The ash after calcination of waste lithium batteries is leached with pure water under ultrasonic conditions, and carbon dioxide is introduced during leaching to convert lithium carbonate into lithium bicarbonate, thereby increasing the concentration of lithium in the solution; S2. Solid-liquid separation of the leaching liquid: The leaching liquid is separated into solid and liquid by a centrifuge to obtain a liquid phase and a solid phase residue, and the solid phase residue can be used to recover other metals later; S3, ultrafiltration purification: The obtained liquid phase is subjected to ultrafiltration pretreatment using a tubular membrane to remove particulate impurities in the solution, and the divalent and above cations in the tubular membrane produced water are removed using a cationic resin to obtain a purified liquid after impurities are removed; S4, reverse osmosis concentration: the purified liquid after impurity removal by resin is subjected to reverse osmosis concentration to increase the concentration of lithium in the solution until lithium bicarbonate is close to saturation, and the reverse osmosis concentrated liquid is subjected to low-temperature pyrolysis to prepare lithium carbonate; S5, decomposition liquid solid-liquid separation: the mother liquor after pyrolysis and the lithium carbonate solid phase are centrifuged and separated by a centrifuge; S6. Preparation of high-purity lithium carbonate by freeze crystallization: freeze-drying the separated solid lithium carbonate in a freeze dryer to remove water and obtain high-purity lithium carbonate; S7, carbon removal: sulfuric acid is added to the lithium precipitation mother liquor after solid-liquid separation, and sulfuric acid reacts with lithium carbonate and lithium bicarbonate to form lithium sulfate, and the solution after carbon removal is evaporated and concentrated; S8. Lithium precipitation: Sodium carbonate is added to the concentrated solution to precipitate solid lithium carbonate. The mother liquor and the lithium carbonate solid phase after lithium precipitation are centrifuged and separated. The solid lithium carbonate is dehydrated and dried to obtain crude lithium carbonate. The solution after solid-liquid separation is discharged from the system.

2. A method for recovering lithium carbonate from calcined ash of waste lithium batteries according to claim 1, characterized in that: The water-cement mass ratio in S1 is 20:1-40:1, and the pH of the solution is 6-9 after the introduction of carbon dioxide.

3. A method for recovering lithium carbonate from calcined ash of waste lithium batteries according to claim 1, characterized in that: The operating pressure of the tubular membrane in S3 is 0.05-0.2MPa.

4. A method for recovering lithium carbonate from calcined ash of waste lithium batteries according to claim 1, characterized in that: The lithium ion concentration of the reverse osmosis concentrate in S4 is 6-7.5g / L.

5. A method for recovering lithium carbonate from calcined ash of waste lithium batteries according to claim 1, characterized in that: The pyrolysis temperature in S4 is 70-90°C.

6. A method for recovering lithium carbonate from calcined ash of waste lithium batteries according to claim 1, characterized in that: The purity of lithium carbonate in S6 is greater than 99.5%.

7. A method for recovering lithium carbonate from calcined ash of waste lithium batteries according to claim 1, characterized in that: The lithium ion concentration of the concentrated solution in S7 is 25-32 g / L.

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