Process for synthesizing high-crystallinity lithium carbonate by carbonization of waste battery leaching solution assisted by photocatalysis

Abstract

The application relates to a process for synthesizing high-crystallinity lithium carbonate through photocatalytic carbonization of waste battery leaching liquor, and belongs to the technical field of waste battery recycling and utilization. A waste ternary lithium ion battery positive electrode material leaching liquor is taken, oxalic acid and a sodium hydroxide solution are added, stirring reaction is carried out, and purified leaching liquor is obtained after filtration; the purified leaching liquor is transferred into a photocatalytic reaction kettle, a photocatalyst is added, carbon dioxide gas is introduced, a light source is started to perform irradiation, and photocatalytic carbonization reaction is carried out; after the reaction is completed, solid-liquid separation, washing and drying are carried out, and high-crystallinity lithium carbonate is obtained; a composite leaching agent is prepared by using deionized water, hydroxyethyl diaminetetraacetic acid trisodium salt, acrylic acid, 2,3-dimercaptosuccinic acid and a photoinitiator; the lithium carbonate prepared by the application has high purity and high lithium recovery rate, and the resource utilization rate is effectively improved.

Description

Technical Field

[0001] This invention relates to the field of waste battery recycling and utilization technology, and in particular to a process for photocatalytically assisted carbonization of waste battery leachate to synthesize highly crystalline lithium carbonate. Background Technology

[0002] Lithium-ion batteries are widely used in electric vehicles, portable electronic devices, and energy storage systems due to their high energy density, long cycle life, and lack of memory effect. However, the rapid development of the lithium-ion battery market has led to a significant waste of resources and environmental problems from the generation of large quantities of discarded lithium-ion batteries.

[0003] Chinese Patent CN120757132A relates to the field of lithium battery material technology, and specifically to a method for preparing battery-grade lithium carbonate from waste lithium batteries. The method includes the following steps: disassembling, crushing, and sieving recycled lithium iron phosphate batteries to obtain lithium battery fragments; leaching the fragments with a choline chloride-citric acid mixed solution, and adding sulfuric acid to inhibit the leaching of iron and phosphorus ions; filtering to obtain a first filtrate and a first filter residue; adding calcium hydroxide to the first filtrate and filtering to obtain a second filtrate and a second filter residue; removing impurities from the second filtrate through activated carbon adsorption and filtering to obtain a third filtrate and a third filter residue; adding hydrochloric acid to the third filtrate to obtain a lithium chloride solution; converting the lithium chloride solution into a lithium carbonate solution through carbonation; subjecting the lithium carbonate solution to gradient crystallization treatment, followed by pulping with pure water and drying to obtain a high-purity lithium carbonate product.

[0004] Chinese Patent CN120943266A discloses lithium orthosilicate, its preparation method and application, and a method for preparing lithium carbonate. The method for preparing lithium orthosilicate includes: discharging and pre-treating waste lithium batteries to obtain waste cathode material powder; pressing the waste cathode material powder into cathode material sheets; stacking the cathode material sheets and silicon dioxide sheets in an electrothermal graphite boat, wherein the silicon dioxide sheets are located on the side of the cathode material sheets away from the electrothermal graphite boat; and performing pulse heating treatment on the electrothermal graphite boat at a temperature of 800℃~1000℃ to obtain the lithium orthosilicate.

[0005] The leachate from existing waste batteries has a complex composition, containing a large number of impurity ions such as iron ions, copper ions, nickel ions, and cobalt ions in addition to lithium ions. These impurities compete with lithium ions to combine with carbonate ions, resulting in a decrease in the purity of lithium carbonate products. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a process for photocatalytically assisted carbonization synthesis of highly crystalline lithium carbonate from waste battery leachate. The operation steps are as follows (in parts by weight): S1 raw material pretreatment: Take 5-10 parts of leachate from waste ternary lithium-ion battery cathode material, add 3-8 parts of composite leachate agent, stir evenly, slowly add sodium hydroxide solution, adjust the pH value of leachate to 4-5, continue stirring and reacting for 30-60 minutes, and filter to obtain purified leachate. S2 photocatalytic carbonization reaction: Transfer 40-60 parts of purified leachate into a photocatalytic reactor, add 0.6-1.2 parts of photocatalyst, add 5-10 wt% sodium hydroxide solution to adjust the pH value to 10-12, introduce carbon dioxide gas, and turn on the light source for irradiation to carry out the photocatalytic carbonization reaction. S3 Post-processing: After the reaction is completed, let the reaction system stand for 30-60 minutes, separate the solid and liquid to obtain crude lithium carbonate, wash the crude product with deionized water 2-4 times, and dry it to obtain highly crystalline lithium carbonate.

[0007] Optionally, the light source for the S2 photocatalytic carbonization reaction is an ultraviolet-visible composite light source, wherein the ultraviolet wavelength is 250-380nm, the visible wavelength is 400-600nm, the light source power is 50-200W, and the irradiation distance is 5-15cm.

[0008] Optionally, the S2 carbon dioxide gas is introduced at a rate of 0.5-2 L / min.

[0009] Optionally, the pressure of the S2 catalytic carbonization reaction is 0.3-0.8 MPa, and the reaction temperature is 40-70℃.

[0010] Optionally, the stirring rate of the S2 photocatalytic carbonization reaction process is 200-500 r / min.

[0011] Optionally, the irradiation time of the light source for the S2 photocatalytic carbonization reaction is 1-3 hours.

[0012] Optionally, in the S3 washing process, the amount of deionized water used each time is 3-5 times the mass of crude lithium carbonate, and the washing is continued until the pH value of the washing solution is 7-8.

[0013] Optionally, the drying temperature of S3 is 100-120℃, and the drying time is 2-4 hours.

[0014] Optionally, the photocatalyst is a nitrogen-doped titanium dioxide / graphene composite material, and its preparation method is as follows: Disperse 5-10 parts of graphene in 500-800 parts of deionized water, add 40-60 parts of tetrabutyl titanate and 5-11 parts of urea, and stir to form a uniform sol; after hydrothermal reaction at 120-180℃ for 4-8 hours, wash, centrifuge and dry to obtain nitrogen-doped titanium dioxide / graphene composite material.

[0015] Optionally, the preparation method of the composite leachate is as follows: A1: Add 100-130 parts of deionized water to the reactor, stir and heat to 50-60℃, add 0.4-0.8 parts of trisodium hydroxyethyldiaminetetraacetate, stir for 15-25 minutes until dissolved; slowly add 11-22 parts of acrylic acid, and after the addition is complete, stir at 50-60℃ for 40-80 minutes. A2: Continue to add 0.6-1.2 parts of 2,3-dimercaptosuccinic acid and 0.6-1.2 parts of photoinitiator 1173, stir for 10-15 minutes, then heat to 70-80℃, and irradiate the reaction under ultraviolet light at 365-405nm and 80-120mW / cm² for 90-120 minutes. Cool to room temperature to obtain the composite leachate.

[0016] Reaction mechanism The composite leaching agent undergoes an amidation condensation reaction to generate an intermediate containing nitrogen and oxygen coordination sites. Subsequently, 2,3-dimercaptosuccinic acid is added to the intermediate, forming a multi-component coordination polymer via a mercapto-olefin click chemistry reaction. This polymer possesses abundant multi-component coordination sites. During the raw material pretreatment stage, this polymer selectively complexes with Li⁺, while effectively adsorbing and separating impurity ions in the leachate. In the photocatalytic carbonization reaction stage, the photocatalyst is activated under specific light source irradiation. This enhances the reactivity of ions in the system and regulates the complexation balance between the multi-component coordination polymer and Li⁺, promoting the efficient combination of Li⁺ and CO₂ under suitable conditions. During this process, the additive formed from the click chemistry reaction products guides the growth of lithium carbonate crystals in a specific orientation through its unique coordination structure, thereby achieving precise control over the crystal growth process.

[0017] Technical effect This invention provides a photocatalytically assisted carbonization process for synthesizing highly crystalline lithium carbonate from leachate from spent batteries. Compared with existing technologies, this invention has the following significant advantages: 1. This invention effectively regulates the growth process of lithium carbonate crystals through the synergistic effect of photocatalytic assisted technology and composite leaching agent, resulting in a product with high purity that can meet the preparation requirements of lithium-ion battery cathode materials.

[0018] 2. In the raw material pretreatment process of this invention, the composite leaching agent can completely remove impurities, and the photocatalytic effect further improves the reactivity of lithium ions, significantly improving the lithium recovery rate and enhancing resource utilization.

[0019] 3. Photocatalysis reduces the pressure and temperature requirements of the carbonization reaction and shortens the reaction cycle, showing significant advantages in energy consumption control and production cost reduction. Attached Figure Description

[0020] Figure 1 This is the SEM image of Example 1. Detailed Implementation

[0021] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with the accompanying drawings and preferred embodiments, is provided below.

[0022] The main components of the leachate from waste ternary lithium-ion battery cathode materials are: Li⁺ concentration 35g / L, Fe³⁺ concentration 2.1g / L, Cu²⁺ concentration 0.8g / L, Ni²⁺ concentration 5.2g / L, and Co²⁺ concentration 4.5g / L.

[0023] 1. Lithium carbonate purity: Detected using inductively coupled plasma atomic emission spectrometry.

[0024] 2. Lithium recovery rate: Detected by inductively coupled plasma atomic emission spectrometry (ICP-AES), using the formula: Lithium recovery rate = (Total mass of Li⁺ in leachate - Total mass of Li⁺ in filtrate) / Total mass of Li⁺ in leachate × 100%. Example 1

[0025] A process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate using photocatalysis, comprising the following steps: S1 raw material pretreatment: Take 5g of leachate from waste ternary lithium-ion battery cathode material, add 3g of composite leachate agent, stir evenly, slowly add sodium hydroxide solution, adjust the pH value of leachate to 4, continue stirring and reacting for 30min, and filter to obtain purified leachate. S2 photocatalytic carbonization reaction: 40g of purified leachate is transferred into a photocatalytic reactor, 0.6g of photocatalyst is added, 5wt% sodium hydroxide solution is added to adjust the pH value to 10, carbon dioxide gas is introduced, and the light source is turned on for irradiation to carry out the photocatalytic carbonization reaction. S3 Post-processing: After the reaction is completed, the reaction system is allowed to stand for 30 minutes, and the solid and liquid are separated to obtain crude lithium carbonate. The crude product is washed twice with deionized water and dried to obtain highly crystalline lithium carbonate.

[0026] The light source for the S2 photocatalytic carbonization reaction is an ultraviolet-visible composite light source, wherein the ultraviolet wavelength is 250nm, the visible wavelength is 400nm, the light source power is 50W, and the irradiation distance is 5cm.

[0027] The rate at which the S2 carbon dioxide gas is introduced is 0.5 L / min.

[0028] The pressure of the S2 catalytic carbonization reaction is 0.3 MPa, and the reaction temperature is 40°C.

[0029] The stirring rate of the S2 photocatalytic carbonization reaction process is 200 r / min.

[0030] The light source irradiation time for the S2 photocatalytic carbonization reaction is 1 hour.

[0031] In the S3 washing process, the amount of deionized water used each time is 3 times the mass of crude lithium carbonate, and the washing is continued until the pH value of the washing solution is 7.

[0032] The drying temperature of S3 is 100℃ and the drying time is 2 hours.

[0033] The photocatalyst is a nitrogen-doped titanium dioxide / graphene composite material, and its preparation method is as follows: 5g of graphene was dispersed in 500g of deionized water, and 40g of tetrabutyl titanate and 5g of urea were added. The mixture was stirred to form a uniform sol. After hydrothermal reaction at 120℃ for 4h, the mixture was washed, centrifuged and dried to obtain nitrogen-doped titanium dioxide / graphene composite material.

[0034] The preparation method of the composite leachate is as follows: A1: Add 100g of deionized water to the reactor, stir and heat to 50℃, add 0.4g of trisodium hydroxyethyldiaminetetraacetate, stir for 15min until dissolved; slowly add 11g of acrylic acid, and after the addition is complete, stir at 50℃ for 40min. A2: Continue to add 0.6g of 2,3-dimercaptosuccinic acid and 0.6g of photoinitiator 1173, stir for 10 min, then heat to 70℃, irradiate with ultraviolet light at 365nm and 80mW / cm² for 90 min, and cool to room temperature to obtain the composite leaching agent. Example 2

[0035] A process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate using photocatalysis, comprising the following steps: S1 raw material pretreatment: Take 6g of leachate from waste ternary lithium-ion battery cathode material, add 4g of composite leachate agent, stir evenly, slowly add sodium hydroxide solution, adjust the pH value of leachate to 4, continue stirring and reacting for 40min, and filter to obtain purified leachate. S2 photocatalytic carbonization reaction: 45g of purified leachate is transferred into a photocatalytic reactor, 0.8g of photocatalyst is added, 6wt% sodium hydroxide solution is added to adjust the pH value to 11, carbon dioxide gas is introduced, and the light source is turned on for irradiation to carry out the photocatalytic carbonization reaction. S3 Post-processing: After the reaction is completed, the reaction system is allowed to stand for 40 minutes, and the solid and liquid are separated to obtain crude lithium carbonate. The crude product is washed three times with deionized water and dried to obtain highly crystalline lithium carbonate.

[0036] The light source for the S2 photocatalytic carbonization reaction is an ultraviolet-visible composite light source, wherein the ultraviolet wavelength is 300nm, the visible wavelength is 450nm, the light source power is 100W, and the irradiation distance is 8cm.

[0037] The rate at which the S2 carbon dioxide gas is introduced is 1 L / min.

[0038] The pressure of the S2 catalytic carbonization reaction is 0.4 MPa, and the reaction temperature is 50 °C.

[0039] The stirring rate of the S2 photocatalytic carbonization reaction process is 300 r / min.

[0040] The light source irradiation time for the S2 photocatalytic carbonization reaction is 2 hours.

[0041] In the S3 washing process, the amount of deionized water used each time is 4 times the mass of crude lithium carbonate, and the washing is continued until the pH value of the washing solution is 7.

[0042] The drying temperature of S3 is 105℃ and the drying time is 3h.

[0043] The photocatalyst is a nitrogen-doped titanium dioxide / graphene composite material, and its preparation method is as follows: 6g of graphene was dispersed in 600g of deionized water, and 45g of tetrabutyl titanate and 7g of urea were added and stirred to form a uniform sol. After hydrothermal reaction at 140℃ for 5h, the sol was washed, centrifuged and dried to obtain nitrogen-doped titanium dioxide / graphene composite material.

[0044] The preparation method of the composite leachate is as follows: A1: Add 110g of deionized water to the reactor, stir and heat to 55℃, add 0.5g of trisodium hydroxyethyldiaminetetraacetate, stir for 20min until dissolved; slowly add 15g of acrylic acid, and after the addition is complete, stir at 55℃ for 50min. A2: Continue to add 0.8g of 2,3-dimercaptosuccinic acid and 0.8g of photoinitiator 1173, stir for 10 min, then heat to 75℃, irradiate with ultraviolet light at 385nm and 90mW / cm² for 100 min, and cool to room temperature to obtain the composite leaching agent. Example 3

[0045] A process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate using photocatalysis, comprising the following steps: S1 raw material pretreatment: Take 8g of leachate from waste ternary lithium-ion battery cathode material, add 7g of composite leachate agent, stir evenly, slowly add sodium hydroxide solution, adjust the pH of leachate to 5, continue stirring and reacting for 50min, and filter to obtain purified leachate. S2 photocatalytic carbonization reaction: 55g of purified leachate is transferred into a photocatalytic reactor, 1g of photocatalyst is added, 8wt% sodium hydroxide solution is added to adjust the pH value to 11, carbon dioxide gas is introduced, and the light source is turned on to irradiate the reaction and carry out the photocatalytic carbonization reaction. S3 Post-processing: After the reaction is completed, the reaction system is allowed to stand for 50 minutes, and the solid and liquid are separated to obtain crude lithium carbonate. The crude product is washed three times with deionized water and dried to obtain highly crystalline lithium carbonate.

[0046] The light source for the S2 photocatalytic carbonization reaction is an ultraviolet-visible composite light source, wherein the ultraviolet wavelength is 350nm, the visible wavelength is 550nm, the light source power is 150W, and the irradiation distance is 13cm.

[0047] The rate at which the S2 carbon dioxide gas is introduced is 1.5 L / min.

[0048] The pressure of the S2 catalytic carbonization reaction is 0.7 MPa, and the reaction temperature is 60°C.

[0049] The stirring rate of the S2 photocatalytic carbonization reaction process is 400 r / min.

[0050] The light source irradiation time for the S2 photocatalytic carbonization reaction is 2 hours.

[0051] In the S3 washing process, the amount of deionized water used each time is 4 times the mass of crude lithium carbonate, and the washing is continued until the pH value of the washing solution is 8.

[0052] The drying temperature of S3 is 115℃ and the drying time is 3 hours.

[0053] The photocatalyst is a nitrogen-doped titanium dioxide / graphene composite material, and its preparation method is as follows: 8g of graphene was dispersed in 700g of deionized water, and 55g of tetrabutyl titanate and 9g of urea were added and stirred to form a uniform sol. After hydrothermal reaction at 160℃ for 6h, the sol was washed, centrifuged and dried to obtain nitrogen-doped titanium dioxide / graphene composite material.

[0054] The preparation method of the composite leachate is as follows: A1: Add 120g of deionized water to the reactor, stir and heat to 55℃, add 0.6g of trisodium hydroxyethyldiaminetetraacetate, stir for 20min until dissolved; slowly add 20g of acrylic acid, and after the addition is complete, stir at 55℃ for 70min. A2: Continue to add 1g of 2,3-dimercaptosuccinic acid and 1g of photoinitiator 1173, stir for 15min, then heat to 75℃, irradiate with ultraviolet light at 395nm and 110mW / cm² for 110min, and cool to room temperature to obtain the composite leachate. Example 4

[0055] A process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate using photocatalysis, comprising the following steps: S1 raw material pretreatment: Take 10g of leachate from waste ternary lithium-ion battery cathode material, add 8g of composite leachate agent, stir evenly, slowly add sodium hydroxide solution, adjust the pH of leachate to 5, continue stirring and reacting for 60min, and filter to obtain purified leachate. S2 photocatalytic carbonization reaction: 60g of purified leachate is transferred into a photocatalytic reactor, 1.2g of photocatalyst is added, 10wt% sodium hydroxide solution is added to adjust the pH value to 12, carbon dioxide gas is introduced, and the light source is turned on for irradiation to carry out the photocatalytic carbonization reaction. S3 Post-processing: After the reaction is completed, the reaction system is allowed to stand for 60 minutes, and the solid and liquid are separated to obtain crude lithium carbonate. The crude product is washed 4 times with deionized water and dried to obtain highly crystalline lithium carbonate.

[0056] The light source for the S2 photocatalytic carbonization reaction is an ultraviolet-visible composite light source, wherein the ultraviolet wavelength is 380nm, the visible wavelength is 600nm, the light source power is 200W, and the irradiation distance is 15cm.

[0057] The rate at which the S2 carbon dioxide gas is introduced is 2 L / min.

[0058] The pressure of the S2 catalytic carbonization reaction is 0.8 MPa, and the reaction temperature is 70 °C.

[0059] The stirring rate of the S2 photocatalytic carbonization reaction process is 500 r / min.

[0060] The light source irradiation time for the S2 photocatalytic carbonization reaction is 3 hours.

[0061] In the S3 washing process, the amount of deionized water used each time is 5 times the mass of crude lithium carbonate, and the washing is continued until the pH value of the washing solution is 8.

[0062] The drying temperature of S3 is 120℃ and the drying time is 4 hours.

[0063] The photocatalyst is a nitrogen-doped titanium dioxide / graphene composite material, and its preparation method is as follows: 10g of graphene was dispersed in 800g of deionized water, and 60g of tetrabutyl titanate and 11g of urea were added. The mixture was stirred to form a uniform sol. After hydrothermal reaction at 180℃ for 8 hours, the mixture was washed, centrifuged and dried to obtain nitrogen-doped titanium dioxide / graphene composite material.

[0064] The preparation method of the composite leachate is as follows: A1: Add 130g of deionized water to the reactor, stir and heat to 60℃, add 0.8g of trisodium hydroxyethyldiaminetetraacetate, stir for 25min until dissolved; slowly add 22g of acrylic acid, and after the addition is complete, stir at 60℃ for 80min. A2: Continue to add 1.2g of 2,3-dimercaptosuccinic acid and 1.2g of photoinitiator 1173, stir for 15min, then heat to 80℃, irradiate with ultraviolet light at 405nm and 120mW / cm² for 120min, and cool to room temperature to obtain the composite leachate.

[0065] Comparative Example 1 A process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate using photocatalysis, comprising the following steps: S1 raw material pretreatment: Take 5g of leachate from waste ternary lithium-ion battery cathode material, slowly add sodium hydroxide solution, adjust the pH of the leachate to 4, continue stirring and reacting for 30 minutes, and filter to obtain purified leachate. S2 photocatalytic carbonization reaction: 40g of purified leachate is transferred into a photocatalytic reactor, 0.6g of photocatalyst is added, 5wt% sodium hydroxide solution is added to adjust the pH value to 10, carbon dioxide gas is introduced, and the light source is turned on for irradiation to carry out the photocatalytic carbonization reaction. S3 Post-processing: After the reaction is completed, the reaction system is allowed to stand for 30 minutes, and the solid and liquid are separated to obtain crude lithium carbonate. The crude product is washed twice with deionized water and dried to obtain highly crystalline lithium carbonate.

[0066] The light source for the S2 photocatalytic carbonization reaction is an ultraviolet-visible composite light source, wherein the ultraviolet wavelength is 250nm, the visible wavelength is 400nm, the light source power is 50W, and the irradiation distance is 5cm.

[0067] The rate at which the S2 carbon dioxide gas is introduced is 0.5 L / min.

[0068] The pressure of the S2 catalytic carbonization reaction is 0.3 MPa, and the reaction temperature is 40°C.

[0069] The stirring rate of the S2 photocatalytic carbonization reaction process is 200 r / min.

[0070] The light source irradiation time for the S2 photocatalytic carbonization reaction is 1 hour.

[0071] In the S3 washing process, the amount of deionized water used each time is 3 times the mass of crude lithium carbonate, and the washing is continued until the pH value of the washing solution is 7.

[0072] The drying temperature of S3 is 100℃ and the drying time is 2 hours.

[0073] The photocatalyst is a nitrogen-doped titanium dioxide / graphene composite material, and its preparation method is as follows: 5g of graphene was dispersed in 500g of deionized water, and 40g of tetrabutyl titanate and 5g of urea were added. The mixture was stirred to form a uniform sol. After hydrothermal reaction at 120℃ for 4h, the mixture was washed, centrifuged and dried to obtain nitrogen-doped titanium dioxide / graphene composite material.

[0074] Comparative Example 2 A process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate using photocatalysis, comprising the following steps: S1 raw material pretreatment: Take 5g of leachate from waste ternary lithium-ion battery cathode material, add 3g of composite leachate agent, stir evenly, slowly add sodium hydroxide solution, adjust the pH value of leachate to 4, continue stirring and reacting for 30min, and filter to obtain purified leachate. S2 photocatalytic carbonization reaction: 40g of purified leachate is transferred into a photocatalytic reactor, 0.6g of photocatalyst is added, 5wt% sodium hydroxide solution is added to adjust the pH value to 10, carbon dioxide gas is introduced, and the light source is turned on for irradiation to carry out the photocatalytic carbonization reaction. S3 Post-processing: After the reaction is completed, the reaction system is allowed to stand for 30 minutes, and the solid and liquid are separated to obtain crude lithium carbonate. The crude product is washed twice with deionized water and dried to obtain highly crystalline lithium carbonate.

[0075] The light source for the S2 photocatalytic carbonization reaction is an ultraviolet-visible composite light source, wherein the ultraviolet wavelength is 250nm, the visible wavelength is 400nm, the light source power is 50W, and the irradiation distance is 5cm.

[0076] The rate at which the S2 carbon dioxide gas is introduced is 0.5 L / min.

[0077] The pressure of the S2 catalytic carbonization reaction is 0.3 MPa, and the reaction temperature is 40°C.

[0078] The stirring rate of the S2 photocatalytic carbonization reaction process is 200 r / min.

[0079] The light source irradiation time for the S2 photocatalytic carbonization reaction is 1 hour.

[0080] In the S3 washing process, the amount of deionized water used each time is 3 times the mass of crude lithium carbonate, and the washing is continued until the pH value of the washing solution is 7.

[0081] The drying temperature of S3 is 100℃ and the drying time is 2 hours.

[0082] The photocatalyst is a nitrogen-doped titanium dioxide / graphene composite material, and its preparation method is as follows: 5g of graphene was dispersed in 500g of deionized water, and 40g of tetrabutyl titanate and 5g of urea were added. The mixture was stirred to form a uniform sol. After hydrothermal reaction at 120℃ for 4h, the mixture was washed, centrifuged and dried to obtain nitrogen-doped titanium dioxide / graphene composite material.

[0083] The preparation method of the composite leachate is as follows: Add 100g of deionized water to the reactor, stir and heat to 50℃, add 0.4g of trisodium hydroxyethyldiaminetetraacetate, stir for 15min until dissolved; slowly add 11g of acrylic acid, and after the addition is complete, stir at 50℃ for 40min to obtain the composite leaching agent.

[0084] Comparative Example 3 A process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate using photocatalysis, comprising the following steps: S1 raw material pretreatment: Take 5g of leachate from waste ternary lithium-ion battery cathode material, add 3g of composite leachate agent, stir evenly, slowly add sodium hydroxide solution, adjust the pH value of leachate to 4, continue stirring and reacting for 30min, and filter to obtain purified leachate. S2 photocatalytic carbonization reaction: 40g of purified leachate is transferred into a photocatalytic reactor, 0.6g of photocatalyst is added, 5wt% sodium hydroxide solution is added to adjust the pH value to 10, carbon dioxide gas is introduced, and the light source is turned on for irradiation to carry out the photocatalytic carbonization reaction. S3 Post-processing: After the reaction is completed, the reaction system is allowed to stand for 30 minutes, and the solid and liquid are separated to obtain crude lithium carbonate. The crude product is washed twice with deionized water and dried to obtain highly crystalline lithium carbonate.

[0085] The light source for the S2 photocatalytic carbonization reaction is an ultraviolet-visible composite light source, wherein the ultraviolet wavelength is 250nm, the visible wavelength is 400nm, the light source power is 50W, and the irradiation distance is 5cm.

[0086] The rate at which the S2 carbon dioxide gas is introduced is 0.5 L / min.

[0087] The pressure of the S2 catalytic carbonization reaction is 0.3 MPa, and the reaction temperature is 40°C.

[0088] The stirring rate of the S2 photocatalytic carbonization reaction process is 200 r / min.

[0089] The light source irradiation time for the S2 photocatalytic carbonization reaction is 1 hour.

[0090] In the S3 washing process, the amount of deionized water used each time is 3 times the mass of crude lithium carbonate, and the washing is continued until the pH value of the washing solution is 7.

[0091] The drying temperature of S3 is 100℃ and the drying time is 2 hours.

[0092] The photocatalyst is a nitrogen-doped titanium dioxide / graphene composite material, and its preparation method is as follows: 5g of graphene was dispersed in 500g of deionized water, and 40g of tetrabutyl titanate and 5g of urea were added. The mixture was stirred to form a uniform sol. After hydrothermal reaction at 120℃ for 4h, the mixture was washed, centrifuged and dried to obtain nitrogen-doped titanium dioxide / graphene composite material.

[0093] The preparation method of the composite leachate is as follows: A1: Add 100g of deionized water to the reactor, stir and heat to 50℃, add 0.4g of trisodium hydroxyethyldiaminetetraacetate, and stir for 15min until dissolved; A2: Continue to add 0.6g of 2,3-dimercaptosuccinic acid and 0.6g of photoinitiator 1173, stir for 10 min, then heat to 70℃, irradiate with ultraviolet light at 365nm and 80mW / cm² for 90 min, and cool to room temperature to obtain the composite leaching agent.

[0094] Table 1. Detection results of lithium carbonate purity and lithium recovery rate in the examples and comparative examples. Lithium carbonate purity (%) Lithium recovery rate (%) Example 1 99.72 99.13 Example 2 99.74 99.16 Example 3 99.79 99.21 Example 4 99.82 99.25 Comparative Example 1 88.91 83.47 Comparative Example 2 95.87 94.39 Comparative Example 3 96.38 95.54 As shown in Table 1, the examples using the process of this invention are significantly superior to the comparative examples in terms of lithium carbonate purity and lithium recovery rate. The lithium carbonate purity in the examples remains at a high level, and the lithium recovery rate is also within the excellent range, while both indicators in the comparative examples are significantly lower. This difference fully demonstrates the key role of the mercapto-olefin click chemistry product auxiliary in the leaching agent: the multi-component coordination polymer formed by this auxiliary can enhance the complexation selectivity for Li⁺, more efficiently separate impurities in the pretreatment stage, and reduce the impact of impurities on subsequent carbonization reactions and product purity; at the same time, its unique coordination structure can enhance the reactivity of Li⁺ under photocatalysis, promoting the full conversion of Li⁺ to lithium carbonate, thereby significantly improving the lithium recovery rate. In contrast, the comparative examples, which did not use this click chemistry product auxiliary, lack an efficient Li⁺ selective complexation and activation mechanism, resulting in product purity and lithium recovery rate that are difficult to achieve ideal results.

[0095] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate using photocatalysis, comprising the following steps, in parts by mass: S1 raw material pretreatment: Take 5-10 parts of leachate from waste ternary lithium-ion battery cathode material, add 3-8 parts of composite leachate agent, stir evenly, slowly add sodium hydroxide solution, adjust the pH value to 4-5, continue stirring and reacting for 30-60 minutes, and filter to obtain purified leachate. S2 photocatalytic carbonization reaction: Transfer 40-60 parts of purified leachate into a photocatalytic reactor, add 0.6-1.2 parts of photocatalyst, add 5-10 wt% sodium hydroxide solution to adjust the pH value to 10-12, introduce carbon dioxide gas, and turn on the light source for irradiation to carry out the photocatalytic carbonization reaction. S3 post-processing: After the reaction is completed, let the reaction system stand for 30-60 minutes, separate the solid and liquid to obtain crude lithium carbonate, wash the crude product with deionized water 2-4 times, and dry it to obtain highly crystalline lithium carbonate. The composite leaching agent is prepared by reacting trisodium hydroxyethyldiaminetetraacetic acid, acrylic acid, 2,3-dimercaptosuccinic acid, and photoinitiator 1173 under ultraviolet light.

2. The process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate according to claim 1, characterized in that: The light source for the S2 photocatalytic carbonization reaction is an ultraviolet-visible composite light source, wherein the ultraviolet light wavelength is 250-380nm, the visible light wavelength is 400-600nm, the light source power is 50-200W, and the irradiation distance is 5-15cm.

3. The process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate according to claim 1, characterized in that: The rate at which the S2 carbon dioxide gas is introduced is 0.5-2 L / min.

4. The process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate according to claim 1, characterized in that: The pressure of the S2 catalytic carbonization reaction is 0.3-0.8 MPa, and the reaction temperature is 40-70℃.

5. The process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate according to claim 1, characterized in that: The stirring rate of the S2 photocatalytic carbonization reaction process is 200-500 r / min.

6. The process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate according to claim 1, characterized in that: The light source irradiation time for the S2 photocatalytic carbonization reaction is 1-3 hours.

7. The process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate according to claim 1, characterized in that: In the S3 washing process, the amount of deionized water used each time is 3-5 times the mass of crude lithium carbonate, and the washing is continued until the pH value of the washing solution is 7-8.

8. The process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate according to claim 1, characterized in that: The drying temperature of S3 is 100-120℃, and the drying time is 2-4 hours.

9. The process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate according to claim 1, characterized in that: The photocatalyst is a nitrogen-doped titanium dioxide / graphene composite material, and its preparation method is as follows: Disperse 5-10 parts of graphene in 500-800 parts of deionized water, add 40-60 parts of tetrabutyl titanate and 5-11 parts of urea, and stir to form a uniform sol; after hydrothermal reaction at 120-180℃ for 4-8 hours, wash, centrifuge and dry to obtain nitrogen-doped titanium dioxide / graphene composite material.

10. The process for synthesizing highly crystalline lithium carbonate by carbonization of waste battery leachate according to claim 1, characterized in that: The preparation method of the composite leachate is as follows: A1: Add 100-130 parts of deionized water to the reactor, stir and heat to 50-60℃, add 0.4-0.8 parts of trisodium hydroxyethyldiaminetetraacetate, stir for 15-25 minutes until dissolved; slowly add 11-22 parts of acrylic acid, and after the addition is complete, stir at 50-60℃ for 40-80 minutes. A2: Continue to add 0.6-1.2 parts of 2,3-dimercaptosuccinic acid and 0.6-1.2 parts of photoinitiator 1173, stir for 10-15 minutes, then heat to 70-80℃, and irradiate the reaction under ultraviolet light at 365-405nm and 80-120mW / cm² for 90-120 minutes. Cool to room temperature to obtain the composite leachate.

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