A method for extracting and recycling lithium from waste electrolyte

Abstract

The present invention belongs to the field of lithium ion battery recovery, and is particularly related to a method for extracting lithium and recycling in a kind of waste electrolyte, mainly comprising the following steps: S1: lithium battery is discharged, disassembled to obtain positive electrode waste; sodium hydroxide is added to soak, and positive electrode powder is obtained after filtration; S2: positive electrode powder is leached using sulfuric acid and 30% hydrogen peroxide with a concentration of 0.3-0.5mol / L, and leachate and leached residue are obtained after filtration; S3: leachate is passed through a resin column using an adsorption resin grafted with a crown ether as an adsorption medium at a flow rate of 2BV / h; S4: resin is desorbed using dilute hydrochloric acid to obtain a lithium-containing solution. The present invention improves the adsorption capacity and adsorption selectivity of the resin to lithium ions by utilizing the coordination between the specific pore structure among crown ether, amino group and resin matrix, and is applied to the recovery of lithium element in lithium ion battery positive electrode materials, and can obtain higher purity lithium, and the recovery rate of lithium is higher.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium-ion battery recycling, and in particular relates to a method for extracting and recycling lithium from waste electrolytes. Background Art

[0002] The rapid development of new energy technologies is leading the transformation of the global energy mix. Lithium-ion batteries, a key technology, have been successfully commercialized and widely used in a variety of fields. In particular, in new energy sectors such as electric vehicles and energy storage systems, lithium-ion batteries have become an indispensable energy storage solution due to their high energy density, long cycle life, and fast charging capabilities. However, as installed lithium-ion battery capacity continues to expand, the amount of used lithium-ion batteries generated is also increasing year by year, posing new environmental challenges.

[0003] If discarded lithium-ion batteries are improperly handled, the heavy metals they contain, such as lithium, cobalt, and nickel, as well as solvents and other organic auxiliary materials, can cause serious environmental pollution, including soil and water sources. At the same time, the recycling and reuse of spent lithium-ion batteries has significant economic and environmental value. Because the metal resources contained in these batteries are limited in nature and expensive, recycling these metals not only reduces the need for new mineral resources and lowers mining costs, but also mitigates environmental damage. Furthermore, controlling secondary pollution and recycling materials during the recycling process are also crucial components of achieving sustainable development and a circular economy.

[0004] Recycling technologies for used lithium-ion batteries primarily include physical separation, biochemical treatment, and chemical treatment. Physical separation involves flotation and grinding. Biochemical treatment utilizes microorganisms to decompose and metabolize battery materials, selectively leaching specific elements. However, this method is still immature and has not yet been put into practical use. Chemical treatment is currently the most widely used recycling method, with extensive research underway. It is primarily categorized into three main types: pyrometallurgical processes, hydrometallurgical processes, and electrode regeneration.

[0005] At present, the main methods for lithium recovery and extraction from lithium-ion batteries include precipitation, membrane separation, adsorption, etc. During precipitation, other metal ions are often co-precipitated, which increases the difficulty of separation and the cost. The membrane separation method also faces the problems of membrane pollution and long separation time. The adsorption method for lithium extraction has the advantages of lower cost, less environmental pollution, high extraction rate and easy continuous operation, but the selectivity, adsorption capacity and mass transfer rate of common adsorbents still need to be further improved. Therefore, according to Li + The structural characteristics of Li + Based on the interaction with the adsorption sites of the adsorbent, new adsorbents are studied and used to obtain high-purity Li + Extremely important.

[0006] Crown ethers containing 12-14 membered rings are good Li + Selective ligands. Currently, relevant studies have selected 12-14 membered crown ethers as Li + selective ligands, using high internal phase surfaces to copolymerize or surface modify Li + Ligand fixation, such as Chinese patent document CN110227424A discloses a preparation method and application of a covalently modified high-density crown ether functionalized porous adsorbent; the steps are: first, prepare a porous polymer PVBC and a porous polymer with surface-branched poly(glycidyl methacrylate), recorded as PVBC-g-PGMA; mix PVBC-g-PGMA and DMF, and add 2AB12C4 after PVBC-g-PGMA is dispersed in DMF; after reacting in a water bath, the obtained product is washed with DMF, ethanol, and double-distilled water in sequence, and vacuum-dried to obtain an aminoethylbenzo-12-crown-4 modified porous adsorbent; the porous adsorbent prepared by this invention effectively improves the adsorption capacity and mass transfer efficiency, solves the problems of low density of active sites and deep embedding of active sites in existing lithium extraction adsorbents, and provides new ideas for the development of efficient lithium extraction adsorbents.

[0007] However, although these materials have good Li + However, on the one hand, its process is relatively complicated and difficult to apply industrially; on the other hand, its adsorption selectivity and adsorption capacity for lithium ions still need to be further improved. Summary of the Invention

[0008] In order to solve the problems existing in the background technology, the present invention provides a method for extracting and recycling lithium from waste electrolytes. The present invention adopts an adsorption resin grafted with crown ether as a specific lithium adsorbent, which can obtain a higher lithium element recovery rate and purity, and then recycle the lithium element through subsequent process processing.

[0009] An object of the present invention is to provide a method for extracting lithium from waste electrolyte, which specifically comprises the following steps:

[0010] S1: Discharging and disassembling the lithium battery to obtain cathode waste; adding sodium hydroxide to soak the cathode waste, with the liquid-solid ratio of sodium hydroxide to cathode waste being 3-10:1, and filtering to obtain cathode powder;

[0011] S2: Leaching the cathode powder with 0.3-0.5 mol / L sulfuric acid and 30% hydrogen peroxide, and filtering to obtain a leachate and leach residue;

[0012] Preferably, in order to help improve the recovery rate and purity of lithium ions, the present invention further includes the steps of adjusting the pH value of the system to 8.5 after the acid leaching process, and filtering after precipitation, the purpose of which is to remove impurity ions and increase the lithium content of the leachate.

[0013] S3: The leachate is passed through a resin column using an adsorption resin grafted with a crown ether as an adsorption medium at a flow rate of 2 BV / h, and the lithium content in the effluent is detected. When the lithium content in the effluent is greater than 0.1 μg / L, the elution is stopped;

[0014] At this point, the resin column is in an adsorption saturation state.

[0015] The adsorption resin grafted with crown ether is prepared by the following method:

[0016] A resin precursor is prepared by conventional suspension polymerization using glycidyl methacrylate (GMA), triallyl isocyanurate (TAIC), azobisisobutyronitrile, and n-heptane as an oil phase and water and polyvinyl alcohol as an aqueous phase at a mass ratio of 3:1 between the aqueous phase and the oil phase; the resin precursor is added to a mixed solution of 2-hydroxymethyl-12-crown-4 and sodium hydride, refluxed under a nitrogen atmosphere, and dried to obtain a crown-etherified adsorption resin; the crown-etherified adsorption resin is subjected to epoxy ring-opening using ethylenediamine, and the adsorption resin grafted with the crown ether is filtered, washed, and dried;

[0017] S4: desorbing the resin with dilute hydrochloric acid to obtain a lithium-containing solution.

[0018] Furthermore, in step S1, the liquid-to-solid ratio of sodium hydroxide to the cathode waste is 10:1.

[0019] Furthermore, the specific conditions of step S2 are as follows: the positive electrode powder obtained in step S1 is added to a dilute sulfuric acid solution with a concentration of 0.3-0.5 mol / L at a liquid-solid ratio of 20 mL-30 mL: 1 g to leach lithium, wherein 1 mL of 30% hydrogen peroxide is added to the dilute sulfuric acid solution; leaching at 55-65 ° C for 120-200 min, adjusting the pH value of the system to 8.5, filtering, and obtaining a leachate and a leach residue.

[0020] Furthermore, in step S3, the rotation speed of the suspension polymerization is 260 r / min, the mass ratio of GMA to TAIC in the oil phase is 5:1, and the mass ratio of n-heptane to GMA is 1:3.

[0021] Furthermore, in step S3, the temperature rise rate of the suspension polymerization is to stir until the particle size is uniform, then heat to 85° C. at a rate of 2° C. / min, and keep warm for 4 hours.

[0022] Furthermore, the crown etherified adsorption resin described in step S3 is prepared by the following method:

[0023] 2-Hydroxymethyl-12-crown-4 and sodium hydride were mixed in a molar ratio of 1:1 to obtain a mixed solution, which was stirred at 55°C for 6 hours under a nitrogen atmosphere. A resin precursor was added to the above mixed solution, and the mass ratio of the resin precursor to 2-hydroxymethyl-12-crown-4 was 6:1. The mixture was refluxed under nitrogen protection for 70 hours, filtered, washed, and dried to obtain a crown-etherified adsorption resin.

[0024] Furthermore, the specific process conditions for epoxy ring opening using ethylenediamine in step S3 are:

[0025] A crown-etherified adsorption resin was soaked in DMF and allowed to swell for 24 hours. Ethylenediamine was then added at a mass ratio of 1:5 crown-etherified resin to ethylenediamine, and the mixture was reacted at 70°C for 5 hours. After completion of the reaction, the mixture was cooled, filtered, washed, and dried to obtain the crown-ether-grafted adsorption resin.

[0026] Furthermore, the specific process of step S4 is as follows: after disassembling the resin column after adsorption in step S3, immersing it in 1 mol / L dilute hydrochloric acid with a liquid-solid ratio of resin to dilute hydrochloric acid of 1:36-40, and shaking and stirring at 25° C. for 4-6 hours to obtain a lithium-containing solution.

[0027] Another object of the present invention is to provide a method for extracting and recycling lithium from waste electrolytes, characterized in that battery-grade lithium carbonate can be obtained by adding sodium carbonate to a lithium-containing solution.

[0028] It should be noted that it is well known in the art that it is difficult to form lithium carbonate products under acidic conditions. In the process of preparing lithium carbonate in the present invention, it is necessary to add an alkaline agent commonly used in the art to adjust the pH of the system to between 7 and 11 and then add carbonate to carry out the preparation process of lithium carbonate. Its role is twofold: one is to neutralize excess acid in the lithium-containing solution; the other is that alkaline conditions are more conducive to the formation of lithium carbonate, thereby improving the final purity of the lithium carbonate product. The alkaline agent described in the present invention can be any alkaline agent commonly used in the art, such as sodium hydroxide.

[0029] The present invention has the following beneficial effects:

[0030] 1. The present invention relies on Li + Based on the structural differences between the lithium ions and the impurity ions, glycidyl methacrylate is used as a monomer, triallyl isocyanurate is used as a polymerization cross-linking agent, and n-heptane is used as a porogen. By adopting an optimized component ratio, a precursor resin with a suitable pore size distribution can be obtained. The rich pore structure in the precursor resin can help improve the adsorption capacity and adsorption selectivity of lithium to a certain extent during the elution process.

[0031] 2. The present invention grafts 2-hydroxymethyl-12-crown-4 onto the precursor resin, thereby retaining the crown ether group in the resin precursor. The crown ether has an electron-rich cavity, and its cavity size is similar to that of Li+ The diameters are relatively close, and they can form very stable complexes with lithium ions. They have high resistance to ion interference and have specific selective adsorption for lithium ions. In addition, the synthesis conditions of the present invention are more stable and can adapt to environmental changes. The surface contains more groups and has a relatively high adsorption capacity.

[0032] 3. After 2-hydroxymethyl-12-crown-4 is grafted onto the precursor resin, the epoxy groups wrapped inside the resin matrix are fully exposed through sufficient swelling. Then, ethylenediamine is used as a functionalizing reagent to open the epoxy ring, and a certain number of amino groups are introduced into the resin matrix. The hydrogen ions generated when the crown ether groups on the resin matrix specifically adsorb lithium can combine with the amino groups in the resin matrix, further improving the resin's adsorption capacity for lithium ions. That is, the present invention further improves the resin's adsorption capacity and adsorption selectivity for lithium ions by utilizing the coordination among the crown ether, amino groups and the specific pore structure in the resin matrix. When applied to the recovery of lithium elements from lithium-ion battery positive electrode materials, high-purity lithium can be obtained with a high lithium recovery rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is the SEM spectrum of the adsorption resin grafted with crown ether prepared in the present invention;

[0034] Figure 2 This is the pore size distribution diagram of the adsorption resin grafted with crown ether prepared in the present invention. DETAILED DESCRIPTION

[0035] The present invention is described in detail below with reference to specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments. Based on the given embodiments, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0036] It should be noted that the adsorption resins grafted with crown ethers described in Examples 1-3 below were all prepared in the following manner:

[0037] Add 1000g of aqueous phase (including 10g of 5% polyvinyl alcohol and the rest is deionized water) to a three-necked flask, stir evenly, heat to 40°C, add the oil phase at a mass ratio of 3:1 between the aqueous phase and the oil phase (the polymerization monomer GMA:TAIC in the oil phase is 5:1, the initiator is azobisisobutyronitrile, the porogen is n-heptane, and the mass ratio of n-heptane to GMA is 1:3), stir at a speed of 260 rpm, and after the particle size is uniform, heat to 85°C at a rate of 2°C / min, keep warm for 4h, filter, and Soxhlet extraction with petroleum ether for 12h to remove the solvent and then dry to obtain a resin precursor.

[0038] 2-Hydroxymethyl-12-crown-4 and sodium hydride were mixed in a molar ratio of 1:1 and stirred at 55°C for 6 hours. The stirring should be carried out under a nitrogen atmosphere. The resin precursor was added to the above solution. The mass ratio of the resin precursor to 2-hydroxymethyl-12-crown-4 was 6:1. The mixture was refluxed under nitrogen protection for 70 hours, filtered, washed, and dried to obtain a crown-etherified adsorption resin.

[0039] The crown ether-grafted adsorption resin was soaked in DMF and fully swelled for 24 hours. Ethylenediamine was then added at a mass ratio of 1:5 and reacted at 70°C for 5 hours. After the reaction was complete, the mixture was cooled, filtered, washed, and dried to obtain the crown ether-grafted adsorption resin.

[0040] The morphology of the prepared adsorption resin grafted with crown ether was characterized by scanning electron microscopy. Figure 1 shown.

[0041] Specific surface area and pore size analysis were performed using low-temperature (77K) nitrogen adsorption-desorption methods. Prior to measurement, the sample was pretreated with high-purity nitrogen at 120°C for 13 hours. The BELSORP-mini II adsorption instrument measured nitrogen adsorption and degassing isotherms at 77K and automatically calculated the average pore size of the resin to be 6.9nm and the specific surface area to be 1025m². 2 / g.

[0042] The present invention measures the content of amino groups in the resin by hydrochloric acid titration. After detection, the amino group content of the adsorption resin grafted with crown ether according to the present invention is 1.6 mmol / g.

[0043] The content of crown ether in the resin was determined by gas chromatography-mass spectrometry (GC-MS). The result showed that the content of crown ether in the adsorption resin grafted with crown ether was 3.1 mmol / g.

[0044] Lithium-ion batteries are mainly composed of a negative electrode sheet, a separator, and a positive electrode sheet. The positive electrode sheet uses aluminum foil as the current collector and is coated with positive electrode materials (active material + conductive agent + binder PVDF) on both sides. It should be noted that the Li content of the waste lithium-ion battery positive electrode material used in the following examples is 7.4%, the Ni content is 20.1%, the Co content is 19.8%, and the Mn content is 21.3%.

[0045] Example 1

[0046] S1: Discharge and disassemble the lithium battery to obtain positive electrode waste; add sodium hydroxide for soaking, and obtain positive electrode powder after filtration with a liquid-solid ratio of sodium hydroxide to positive electrode waste of 3:1.

[0047] S2: The positive electrode powder obtained in step S1 was added to a 0.3 mol / L dilute sulfuric acid solution with a liquid-solid ratio of 20 mL:1 g to extract lithium, and 1 mL of 30% hydrogen peroxide was added to the dilute sulfuric acid solution; the mixture was leached at 60°C for 180 min, the pH value of the system was adjusted to 8.5, and then filtered to obtain a leachate and a leach residue.

[0048] S3: The leachate is passed through an adsorption column using an adsorption resin grafted with crown ether as the adsorption medium at a flow rate of 2BV / h, and the lithium content in the effluent is detected. When the lithium content in the effluent is greater than 0.1ug / L, elution is stopped. At this time, the resin is in an adsorption saturation state.

[0049] S4: dismantle the resin column after adsorption saturation in step S3, soak it in 1 mol / L dilute hydrochloric acid with a solid-liquid ratio of resin to dilute hydrochloric acid of 1:36, and shake and stir at 25° C. for 4 hours to obtain a lithium-containing solution.

[0050] Example 2

[0051] S1: Discharge and disassemble the lithium battery to obtain positive electrode waste; add sodium hydroxide for soaking, and obtain positive electrode powder after filtration with a liquid-solid ratio of sodium hydroxide to positive electrode waste of 5:1.

[0052] S2: The positive electrode powder obtained in step S1 was added to a 0.5 mol / L dilute sulfuric acid solution at a liquid-solid ratio of 25 mL:1 g to extract lithium, and 1 mL of 30% hydrogen peroxide was added to the dilute sulfuric acid solution; the mixture was leached at 55°C for 200 min, the pH value of the system was adjusted to 8.5, and then filtered to obtain a leachate and a leach residue.

[0053] S3: The leachate is passed through an adsorption column using an adsorption resin grafted with crown ether as the adsorption medium at a flow rate of 2BV / h, and the lithium content in the effluent is detected. When the lithium content in the effluent is greater than 0.1ug / L, elution is stopped. At this time, the resin is in an adsorption saturation state.

[0054] S4: dismantle the resin column after adsorption saturation in step S3, soak it in 1 mol / L dilute hydrochloric acid with a solid-liquid ratio of resin to dilute hydrochloric acid of 1:40, and shake and stir at 25° C. for 5 hours to obtain a lithium-containing solution.

[0055] Example 3

[0056] S1: Discharge and disassemble the lithium battery to obtain positive electrode waste; add sodium hydroxide for soaking, and filter to obtain positive electrode powder after the liquid-solid ratio of sodium hydroxide to positive electrode waste is 10:1.

[0057] S2: The positive electrode powder obtained in step S1 was added to a 0.3 mol / L dilute sulfuric acid solution at a liquid-solid ratio of 30 mL:1 g to extract lithium, and 1 mL of 30% hydrogen peroxide was added to the dilute sulfuric acid solution; the mixture was leached at 65°C for 120 min, the pH value of the system was adjusted to 8.5, and then filtered to obtain a leachate and a leach residue.

[0058] S3: The leachate is passed through an adsorption column using an adsorption resin grafted with crown ether as the adsorption medium at a flow rate of 2BV / h, and the lithium content in the effluent is detected. When the lithium content in the effluent is greater than 0.1ug / L, elution is stopped. At this time, the resin is in an adsorption saturation state.

[0059] S4: After the resin column is saturated with adsorption in step S3, it is disassembled and immersed in 1 mol / L dilute hydrochloric acid with a solid-liquid ratio of resin to dilute hydrochloric acid of 1:40. The mixture is shaken and stirred at 25° C. for 6 h to obtain a lithium-containing solution.

[0060] Comparative Example 1

[0061] The adsorption resin grafted with crown ether described in this comparative example was prepared by the following method

[0062] Add 1000g of aqueous phase (including 10g of 5% polyvinyl alcohol and the rest is deionized water) to a three-necked flask, stir evenly, heat to 40°C, add the oil phase at a mass ratio of 3:1 between the aqueous phase and the oil phase (the polymer monomer GMA:TAIC in the oil phase is 5:1, the initiator is azobisisobutyronitrile, the porogen is n-heptane, and the mass ratio of n-heptane to the polymer monomer is 1:3), stir at a speed of 260 rpm, heat to 85°C at a rate of 2°C / min, and keep warm for 4h, filter, remove the solvent with petroleum ether through Soxhlet extraction, and dry to obtain a resin precursor.

[0063] 2-Hydroxymethyl-12-crown-4 and sodium hydride were mixed in a molar ratio of 1:1 and stirred at 55°C for 6 hours. The stirring should be carried out under a nitrogen atmosphere. The resin precursor was added to the above solution. The mass ratio of the resin precursor to 2-hydroxymethyl-12-crown-4 was 6:1. The mixture was refluxed under nitrogen protection for 70 hours, filtered, washed, and dried to obtain a crown-etherified adsorption resin.

[0064] The specific process conditions for recycling lithium element in this comparative example are as follows:

[0065] S1: Discharge and disassemble the lithium battery to obtain positive electrode waste; add sodium hydroxide for soaking, and filter to obtain positive electrode powder after the liquid-solid ratio of sodium hydroxide to positive electrode waste is 5:1;

[0066] S2: The positive electrode powder obtained in step S1 was added to a 0.5 mol / L dilute sulfuric acid solution at a liquid-solid ratio of 25 mL:1 g to extract lithium, and 1 mL of 30% hydrogen peroxide was added to the dilute sulfuric acid solution; the mixture was leached at 55°C for 200 min, the pH value of the system was adjusted to 8.5, and then filtered to obtain a leachate and a leach residue.

[0067] S3: The leachate is passed through an adsorption column using a crown etherified adsorption resin as the adsorption medium at a flow rate of 2BV / h, and the lithium content in the effluent is detected. When the lithium content in the effluent is greater than 0.1ug / L, elution is stopped. At this time, the resin is in an adsorption saturation state.

[0068] S4: After the resin column is saturated with adsorption in step S3, it is disassembled and immersed in 1 mol / L dilute hydrochloric acid with a solid-liquid ratio of resin to dilute hydrochloric acid of 1:40. The mixture is shaken and stirred at 25° C. for 5 h to obtain a lithium-containing solution.

[0069] The lithium content and recovery rate related indicators before and after treatment with the adsorption resin grafted with crown ether in the examples and comparative examples are shown in the following table:

[0070] Examples and Comparative Examples Example 1 Example 2 Example 3 Comparative Example 1 Lithium content in leachate (%) 38.3 36.9 38.6 36.9 Lithium content of analytical solution (%) 95.3 96.8 96.7 87.6 Lithium recovery rate (%) 95.6 98.7 97.3 88.9

[0071] By comparing the data of the embodiments and the comparative examples, it can be seen that in Examples 1-3, after grafting 2-hydroxymethyl-12-crown-4 on the precursor resin, the epoxy groups wrapped in the resin matrix are fully exposed by sufficient swelling, and then the epoxy is ring-opened using ethylenediamine as a functionalizing reagent, and a certain number of amino groups can be introduced into the resin matrix. The hydrogen ions generated when the crown ether groups on the resin matrix specifically adsorb lithium can be combined with the amino groups in the resin matrix, further improving the adsorption capacity of the resin for lithium ions; that is, the present invention further improves the adsorption capacity and adsorption selectivity of the resin for lithium ions by utilizing the coordination between the crown ether, the amino group and the specific pore structure in the resin matrix, and is applied to the recovery of lithium elements from lithium-ion battery positive electrode materials, thereby obtaining high-purity lithium and having a high lithium recovery rate.

Claims

1. A method for extracting lithium from waste electrolyte, characterized in that: The steps include: S1: Discharging and disassembling the lithium battery to obtain cathode waste; adding sodium hydroxide to soak the cathode waste, with the liquid-solid ratio of sodium hydroxide to cathode waste being 3-10:1, and filtering to obtain cathode powder; The active material in the positive electrode waste includes one or more of LiCoO2, LiNiO2, and LiMnO2; S2: Leaching the cathode powder with 0.3-0.5 mol / L sulfuric acid and 30% hydrogen peroxide, and filtering to obtain a leachate and leach residue; S3: The leachate is passed through a resin column using an adsorption resin grafted with a crown ether as an adsorption medium at a flow rate of 2 BV / h, and the lithium content in the effluent is detected. When the lithium content in the effluent is greater than 0.1 ug / L, the elution is stopped, and the resin column is in an adsorption saturation state; The adsorption resin grafted with crown ether is prepared by the following method: A resin precursor is prepared by suspension polymerization using glycidyl methacrylate, triallyl isocyanurate, azobisisobutyronitrile, and n-heptane as an oil phase and water and polyvinyl alcohol as an aqueous phase at a mass ratio of the aqueous phase to the oil phase of 3:1; the resin precursor is added to a mixed solution of 2-hydroxymethyl-12-crown-4 and sodium hydride, refluxed under a nitrogen atmosphere, and dried to obtain a crown-etherified adsorption resin; the crown-etherified adsorption resin is subjected to epoxy ring opening using ethylenediamine, and the adsorption resin grafted with the crown ether is filtered, washed, and dried; S4: desorbing the resin with dilute hydrochloric acid to obtain a lithium-containing solution; In step S3, the rotation speed of the suspension polymerization is 260 r / min, the mass ratio of glycidyl methacrylate to triallyl isocyanurate in the oil phase is 5:1, and the mass ratio of n-heptane to glycidyl methacrylate is 1:3; the specific process conditions for epoxy ring opening using ethylenediamine in step S3 are: Take the crown etherified adsorption resin, soak it in DMF, and fully swell it for 24 hours. Then, add ethylenediamine in a mass ratio of 1:5 of crown etherified resin: ethylenediamine, and react at 70°C for 5 hours. After the reaction is completed, cool, filter, wash, and dry to obtain the adsorption resin grafted with crown ether.

2. A method for extracting lithium from waste electrolyte according to claim 1, characterized in that: In step S1, the liquid-to-solid ratio of sodium hydroxide to the cathode waste is 10:

1.

3. The method for extracting lithium from waste electrolyte according to claim 1, wherein: The specific conditions of step S2 are as follows: the positive electrode powder obtained in step S1 is added to a dilute sulfuric acid solution with a concentration of 0.3-0.5 mol / L at a liquid-solid ratio of 20 mL-30 mL:1 g to leach lithium, wherein 1 mL of 30% hydrogen peroxide is added to the dilute sulfuric acid solution; leaching is carried out at 55-65° C. for 120-200 minutes, the pH value of the system is adjusted to 8.5, and the solution is filtered to obtain a leachate and a leach residue.

4. The method for extracting lithium from waste electrolyte according to claim 1, wherein: In step S3, the temperature rise rate of the suspension polymerization is: after stirring until the particle size is uniform, the temperature is raised to 85° C. at a rate of 2° C. / min and kept at this temperature for 4 hours.

5. The method for extracting lithium from waste electrolyte according to claim 1, wherein: The crown-etherified adsorption resin described in step S3 is prepared by the following method: 2-Hydroxymethyl-12-crown-4 and sodium hydride were mixed in a molar ratio of 1:1 to obtain a mixed solution, which was stirred at 55°C for 6 hours under a nitrogen atmosphere. A resin precursor was added to the mixed solution, and the mass ratio of the resin precursor to 2-hydroxymethyl-12-crown-4 was 6:

1. The mixture was refluxed under nitrogen protection for 70 hours, filtered, washed, and dried to obtain a crown-etherified adsorption resin.

6. The method for extracting lithium from waste electrolyte according to claim 1, wherein: The specific process of step S4 is as follows: after disassembling the resin column saturated with adsorption in step S3, immersing it in 1 mol / L dilute hydrochloric acid with a solid-liquid ratio of resin to dilute hydrochloric acid of 1:36-40, and shaking and stirring at 25° C. for 4-6 hours to obtain a lithium-containing solution.

7. A method for extracting lithium from waste electrolyte according to claim 6, characterized in that: The solid-liquid ratio of resin to dilute hydrochloric acid was 1:36, and the mixture was shaken and stirred at 25°C for 6 h.

8. A method for extracting and recycling lithium from waste electrolytes, characterized in that: Add carbonate to the lithium-containing solution obtained by the method according to any one of claims 1 to 7 to obtain battery-grade lithium carbonate.

Images