Method for treating electrolyte after wet crushing of waste lithium ion battery

Abstract

The invention discloses a treatment method of an electrolyte after wet crushing of a waste lithium ion battery. During crushing, an alkaline solution is sprayed out of a spraying opening located above a shearing opening to completely cover the waste lithium ion battery crushed material, a hydrolysis reaction is carried out under the cooperation of ultrasonic waves, and waste water, a pole piece mixture, a shell pile head, a diaphragm and the like are separated out through hydrodynamic force. The method comprises the following steps: adding dilute acid into wastewater to adjust the pH value, adding bivalent iron salt and hydrogen peroxide, performing Fenton oxidation and mineralization on an organic solvent in the wastewater under the synergism of ultrasonic waves, then adding an alkali metal salt solution to adjust the pH value, and filtering and separating to obtain filtrate and ferric hydroxide precipitate; adding alkali into the filtrate twice to adjust the pH value for precipitation, and filtering to separate valuable precipitate and filtrate; and adding dilute acid into the ferric hydroxide precipitate for dissolving, and then adding a reducing agent to obtain a ferrous salt solution which is circularly used for Fenton reaction. According to the method, hydrolysis, Fenton oxygenolysis, mineralization of the organic electrolyte and regeneration and recycling of the ferrous salt are adopted, and the method is suitable for large-scale and low-cost treatment of the electrolyte in the waste lithium ion battery.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion battery recycling, and in particular to a method for treating electrolyte after wet crushing of waste lithium ion batteries. Background Art

[0002] With the rapid development of the new energy vehicle industry, the amount of waste electrolyte generated when power batteries are retired is huge, which poses major challenges in terms of environmental protection, safety and economy of recycling technology.

[0003] The organic liquid electrolyte used in lithium-ion batteries is an electrolyte solution formed by dissolving lithium salts in an organic aprotic mixed solvent. Its main components and hazards are as follows:

[0004] (1) Lithium salt (LiPF6 is highly dangerous): Currently, LiPF6 is the main lithium salt used as the electrolyte for commercial lithium-ion batteries. LiPF6 is very sensitive and will immediately react to produce HF gas even when it encounters trace amounts of water. The reaction formula is as follows:

[0005] LiPF6 + H2O = LiF(s) +2HF + POF3

[0006] The three fluoride ions (F - ) Continue to react with H2O, gradually replaced by water hydroxide (OH - ) is replaced, and HF and H3PO4 are finally generated through a series of reactions.

[0007] (2) Toxicity of organic solvent system:

[0008] i) Cyclic carbonates: such as ethylene carbonate (EC, boiling point 238°C). Long-term exposure requires caution because its metabolites may affect the liver and kidneys.

[0009] ii) Linear carbonates: These include dimethyl carbonate (DMC, flash point 18°C, boiling point 90°C), which is suspected of being reproductively toxic; diethyl carbonate (DEC, flash point 33°C, boiling point 126.8°C), which is poorly soluble in water and has some toxicity; and ethyl methyl carbonate (EMC, flash point 23°C, boiling point 108°C), which has poor thermal stability. These linear carbonates can enter the human body through the skin, mucous membranes, or by inhalation, causing local irritation or systemic toxicity. Low concentrations can cause discomfort such as difficulty breathing, dizziness, fatigue, and nausea. Long-term exposure or inhalation of high concentrations can damage the liver, affecting liver function. Excessive exposure can be life-threatening.

[0010] iii) Additives: Linear carboxylates such as methyl formate and methyl acetate, which can significantly improve the low-temperature performance of the electrolyte, are highly toxic. Long-term exposure to low concentrations can lead to lung damage and central nervous system depression. The latter can cause coma or organ failure in severe cases. Another example is vinylene carbonate (VC) and fluoroethylene carbonate (FEC), which improve the stability of the negative electrode SEI film. Long-term exposure to or inhalation of high concentrations of vinylene carbonate may cause damage to multiple systems such as the nervous system and digestive system.

[0011] (3) Overall characteristics and hazards of waste electrolytes: Carbonates in waste lithium-ion battery electrolytes have stable molecular structures, high salt content, and high COD, and are classified as biodegradable organic wastewater. These carbonate organic substances are harmful to the human body. If discharged directly into the environment without treatment, they will cause the COD of water bodies to rise. They have poor biodegradability and seriously endanger the environment and human health. They must be decomposed and treated before they can be discharged.

[0012] After long-term recycling, the electrolyte in used lithium-ion batteries is basically in a state of no electrolyte, and most of the electrolyte is adsorbed in the micropores inside the positive and negative electrode materials and inside the separator. This special state leads to obvious defects in traditional recycling methods:

[0013] (1) Limitations of the crushing and sorting method: If only crushing and sorting methods are used to recycle used lithium-ion batteries, only low-boiling-point organic matter will evaporate during the recycling process, while most of the organic solvents in the electrolyte will still penetrate deeply into the positive and negative electrode materials and the separator. This will cause the organic solvents to continue to evaporate and overflow into the environment during subsequent storage and transportation, posing a high risk of flammability and explosion.

[0014] (2) Interference with hydrometallurgical processes: Residual organic solvents react violently with inorganic strong acids (such as sulfuric acid and hydrochloric acid) during subsequent hydrometallurgical leaching. On the one hand, this may aggravate the production of toxic gases such as HF. On the other hand, it may seriously interfere with the stable progress of the leaching process and cause undue impact on the workers and the surrounding environment.

[0015] Currently, the treatment methods for waste lithium-ion battery electrolytes are divided into pyrolysis and physical treatment.

[0016] The pyrolysis method involves crushing used lithium-ion batteries under a nitrogen atmosphere, then pyrolyzing the crushed material at high temperatures (usually >500°C). This volatilizes and carbonizes the electrolyte in the lithium-ion batteries at high temperatures. The resulting VOCs are then treated through secondary combustion and then meet emission standards. The pyrolysis process is relatively simple, with processing capacity reaching 10,000 tons, making it suitable for all types of used lithium-ion batteries. However, it suffers from high energy consumption and costs, complex tail gas treatment and the risk of secondary pollution, as well as high equipment investment and operating costs. The high-temperature pyrolysis process consumes significant energy, and the tail gas from the pyrolysis contains a variety of hazardous substances, such as volatile organic compounds (VOCs). A secondary combustion treatment unit is required to decompose the VOCs, increasing equipment investment and operational complexity. There is also the risk of incomplete tail gas treatment. Furthermore, the pyrolysis method requires large equipment investment and relatively high operating costs.

[0017] Physical methods involve separating organic solvents from spent lithium-ion batteries through freezing, distillation, centrifugation, extraction, and other methods for recycling. The main advantage of this method is that it theoretically avoids high temperatures and chemical reagents, aiming to recover the solvent. However, it suffers from drawbacks such as complex solvent composition and difficulty in separation, low product value and lack of market demand, and poor economic viability. It has been reported that 18 decomposition products can be analyzed from lithium-ion battery electrolytes after cycling experiments. Various carbonates generate complex derivative compounds, resulting in a large number of impurities in the used electrolyte. Carbonate derivatives generally have similar boiling points, making precise separation difficult by distillation, resulting in low purity of the recovered product. The complex composition and diverse products of the recovered electrolyte make it difficult to generate market demand for the various derivatives, limiting their practical application value. Furthermore, the economic benefits are insufficient relative to the investment, and the production of multiple products requires a large-scale recycling project to generate economic benefits, making it difficult to guarantee economic viability in practice. Currently, there are no established cases for recycling spent lithium-ion battery electrolytes. Even if there are recycling projects that collect some electrolytes through physical methods, they are still burned by fire and then discharged, failing to truly achieve the goal of recycling. Summary of the Invention

[0018] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method for treating the electrolyte after wet crushing of waste lithium-ion batteries, which reduces costs and improves treatment efficiency and safety.

[0019] The specific technical solutions adopted in the present invention are as follows:

[0020] A method for treating electrolytes after wet crushing of waste lithium-ion batteries consists of four steps: spraying an alkaline solution during the live crushing of waste lithium-ion batteries, alkali neutralization, Fenton oxidation of electrolyte-containing wastewater, and regeneration and recycling of divalent iron salts. The alkaline solution is sprayed simultaneously during the crushing of the waste lithium-ion batteries, and the distribution of the spray ports ensures that the alkaline solution can fully cover the crushed materials, preventing the lithium-containing negative electrode crushed materials from being exposed to the air and causing fire. Secondly, the electrolyte volatilization is prevented from polluting the surrounding environment. Because the main components of the electrolyte are insoluble in water, the electrolyte will float on the water surface and continue to evaporate. The synergistic effect of the alkaline solution and ultrasound rapidly and efficiently decomposes carbonates, and the alcoholic organic matter produced by the decomposition is soluble in water. Thirdly, through the cavitation effect of ultrasound, the organic solvent that has deeply penetrated into the positive and negative electrode materials and the diaphragm is oscillated, migrated, and diffused into the alkaline solution, significantly reducing the organic solvent content in the positive and negative electrode materials and the diaphragm. Finally, under the synergistic effect of ultrasound, the Fenton reaction between hydrogen peroxide and Fe(II) generates highly oxidizing hydroxyl radicals (OH • ), its oxidation potential E°(OH • / H2O) up to 2.70V, which can oxidize and decompose alcohol compounds, achieving the goal of mineralizing and decomposing almost all electrolytes. The hydrolysis method and Fenton oxidation method work synergistically, and the COD removal rate of organic electrolytes can reach more than 90%. The wet treatment method involved does not use high-temperature pyrolysis to volatilize the electrolyte and secondary combustion to decompose the tail gas. After the electrolyte wastewater is oxidized and mineralized by the Fenton agent, the agent is simply regenerated and can be recycled for the Fenton reaction, reducing the cost of wastewater treatment. The treatment method specifically includes the following steps:

[0021] S1. Charged crushing and alkali solution spray coverage: Several rows of spray ports are set above the crusher shear port. When shearing the charged waste lithium-ion batteries, an alkali metal hydroxide solution is sprayed simultaneously to completely cover the crushed material with the alkali metal hydroxide solution. The size of the crushed material is 5-45mm.

[0022] S2 ultrasonic synergistic hydrolysis: The crushed material obtained in step S1 is mixed with an alkali metal hydroxide solution into a hydrolysis tank, and the hydrolysis reaction is carried out under ultrasonic and stirring conditions with a power intensity of 5-40W / cm² to decompose the carbonate organic matter in the electrolyte;

[0023] S3. Hydrodynamic separation: The hydrolyzed material from step S2 is separated by a hydrodynamic separation device to separate a heavy component including the shell and pile head, a medium component including the electrode mixture, and a light component including the diaphragm. The electrolyte-containing wastewater generated during the separation process is collected, including centrifugal filtrates and washing wastewater from the low, medium, and high outlets of the separator.

[0024] S4. Fenton oxidation degradation: Add dilute acid to the wastewater obtained in step S3 to adjust the pH value to 2.5-5.0, add 0.2mmol / L-1mol / L divalent iron salt solution, and then press hydrogen peroxide and Fe 2+ Hydrogen peroxide is added in a molar ratio of 1-3:1, and a Fenton oxidation reaction is carried out in an oxidation reactor under the synergy of ultrasonic waves with a power intensity of 50-100W / cm² at a reaction temperature of 20-35°C;

[0025] S5 precipitation separation: after the Fenton reaction in step S4, an alkali metal salt solution was added to the wastewater to adjust the pH value to 4.5-6.0, the wastewater was heated, air was introduced to oxidize the precipitate, and the precipitate was filtered to obtain iron hydroxide and the filtrate;

[0026] S6. Regeneration of ferrous salt: adding dilute acid to dissolve the ferric hydroxide precipitate obtained in step S5, and then adding a reducing agent to react to obtain a ferrous salt solution, which is recycled for step S4;

[0027] S7. Fluoride and phosphorus precipitation in steps: Under stirring, add a Group IIA metal hydroxide emulsion to the filtrate obtained in step S5, and adjust the pH value twice. The first time, adjust the pH to 6.0-8.0 (preferably 7.5-8.0) to precipitate fluoride, and filter and separate the precipitate and filtrate; the second time, adjust the pH to 8.0-10.0 (preferably 9.5-10.0) to precipitate hydrogen phosphate; and filter and separate the precipitate and filtrate.

[0028] Furthermore, in step S1, shearing refers to shearing the charged lithium-ion batteries at one time under the premise of spraying the alkali metal hydroxide solution to fully cover the waste lithium-ion battery materials, and the lithium batteries do not need to be discharged in advance; the shearing is a single shearing, and the size range of the material after crushing is controlled within 5~45mm, thereby minimizing the generation of fine particles.

[0029] Furthermore, in step S1, the spray ports are arranged in 1-8 rows, preferably 4-6 rows, the length of each row of spray ports is greater than the length of the shearing opening, and the total width of the spraying row is greater than the width of the shearing opening. The total length and total width of the spraying row ensure that the sprayed alkaline solution can fully cover the crushed material.

[0030] Furthermore, the crusher shear opening is located above the hydrolysis tank, so that the crusher shear opening is not immersed in the alkali metal hydroxide solution.

[0031] Furthermore, in steps S1 and S2, the mass fraction of the alkali metal hydroxide solution is 0.05%-30%, and the alkali metal hydroxide is preferably sodium hydroxide, potassium hydroxide, or lithium hydroxide.

[0032] The electrolyte in the electrolyte is sensitive to moisture and decomposes in water, eventually generating lithium fluoride, hydrofluoric acid and phosphoric acid. In the presence of alkali, the following reaction occurs (using NaOH as an example):

[0033] LiPF6+ 8NaOH= LiF + 5NaF + Na3PO4 + 4H2O,

[0034] One-fifth of the fluoride ions in the electrolyte react with lithium to form water-insoluble lithium fluoride, which enters the electrode mixture; the remaining fluoride ions react with alkali to form water-soluble sodium fluoride, which enters the wastewater together with sodium phosphate.

[0035] Carbonate organic matter in the electrolyte, including cyclic carbonates and linear carbonates, can undergo decomposition reactions with alkali, mainly the hydrolysis reaction of cyclic ethylene carbonate (EC) and ethyl methyl carbonate (EMC) with alkali.

[0036] Cyclic ethylene carbonate (EC) decomposes with alkali (such as sodium hydroxide) to produce ethylene glycol and sodium carbonate:

[0037] C3H4O3 + 2NaOH = HOCH2CH2OH + Na2CO3,

[0038] The hydroxyl ion in sodium hydroxide acts as a nucleophile to attack the carbonyl carbon in the cyclic carbonate, causing the ring to break and form an alkoxide intermediate, which is then protonated in aqueous solution to form ethylene glycol, while releasing carbonate ions, which combine with sodium ions to form sodium carbonate.

[0039] Diethanol is miscible with water because the resulting ethylene glycol molecule contains two polar hydroxyl groups (-OH), which are similar in structure to water molecules (H2O), following the "like dissolves like" principle. Hydrogen bonds can be formed between the hydroxyl groups and water, significantly enhancing solubility. Compared with monohydroxy alcohols (such as ethanol), the hydrogen bonding effect of ethylene glycol is stronger.

[0040] The decomposition reaction of linear carbonate (taking ethyl methyl carbonate as an example) and alkali (taking sodium hydroxide as an example) produces methanol, ethanol and sodium carbonate:

[0041] CH3OCOOCH2CH3 + 2NaOH = CH3OH + CH3CH2OH + Na2CO3,

[0042] The hydroxyl ion in NaOH acts as a nucleophile to attack the carbonyl carbon in the carbonate, causing the ester bond to break and generate the corresponding alcohol and carbonate. Methanol and ethanol are both miscible with water.

[0043] Hydrolysis and ultrasonic high-frequency vibration work together to produce local high-temperature and high-pressure "cavitation bubbles". The energy released when they burst can destroy the mass transfer resistance at the liquid-solid interface and the liquid-liquid interface, especially diffusing the electrolyte organic solvent that has penetrated into the compacted electrode surface active material into the liquid phase, accelerating the contact between the alkaline reactant OH- and the carbonate molecules, and improving the efficiency of the hydrolysis reaction.

[0044] Furthermore, in step S4, the dilute acid is an inorganic acid or an organic acid, such as phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, etc.; an organic acid such as formic acid, acetic acid, oxalic acid, malonic acid, lactic acid, tartaric acid, etc.; the dilute acid is preferably used to adjust the pH value to 3.0-4.0.

[0045] The direct electron transfer between H2O2 and Fe(Ⅱ) generates hydroxyl radicals (OH • ) is produced, and the reaction formula is as follows:

[0046] Fe 2+ + H2O2 → Fe 3+ + OH • + OH - ,

[0047] The strong oxidizing hydroxyl radical (OH • ), which can attack organic matter indiscriminately. Dimethyl carbonate (DMC) and diethyl carbonate (DEC) that are not fully hydrolyzed in step S2 are oxidized and decomposed into methanol and ethanol. These small molecules of methanol and ethanol, together with the methanol, ethanol and ethylene glycol produced by the hydrolysis and decomposition in step S2, are oxidized and decomposed into methanol and ethanol. • ) is further oxidized into formaldehyde (acetaldehyde), and then further oxidized into formic acid (acetic acid), and finally CO2 and H2O are generated.

[0048] Fenton oxidation is carried out in conjunction with ultrasound. When ultrasound propagates in the liquid, it produces high-frequency vibrations, triggering a "cavitation effect" and generating tiny bubbles in the liquid. When the microbubbles collapse instantly, they generate local high temperature and high pressure, accelerating the decomposition of H2O2 and increasing the activity of hydroxyl radicals (OH • ) yield.

[0049] Cavitation shock waves can directly break the ester bond (CO bond) of carbonates and the CC bond of alcohols, reducing the molecular stability and making them more susceptible to hydroxyl radicals (OH • ) attack, reducing the amount of Fenton reagents used and correspondingly reducing operating costs.

[0050] Fe in the Fenton reaction 2+ Oxidized to Fe 3+ Afterwards, the local reducing environment (such as H • Free radicals) may convert some Fe 3+ Reduction to Fe 2+ , extending the life of the catalyst.

[0051] Under the synergistic effect of Fenton oxidation and ultrasound, the oxidation pathway of alcohols is as follows:

[0052] Methanol → Formaldehyde → Formic acid → CO2,

[0053] Ethanol → acetaldehyde → acetic acid → CO2.

[0054] Furthermore, in step S2, ultrasonic vibration plates are arranged on both sides of the hydrolysis tank; in step S4, ultrasonic vibration plates are distributed around the reactor.

[0055] Furthermore, in step S5, the alkali metal salt is preferably an alkali metal carbonate, more preferably lithium carbonate, sodium carbonate, or potassium carbonate; and the mass fraction of the alkali metal salt solution is 0.5% to 20%.

[0056] Furthermore, in step S6, the dilute acid is phosphoric acid, sulfuric acid, nitric acid and hydrochloric acid, preferably phosphoric acid and sulfuric acid.

[0057] Furthermore, in step S6, the reducing agent is one of sulfur dioxide, carbon monoxide, iron powder, sodium sulfite (Na2SO3), sodium dithionite (Na2S2O4) belonging to the inorganic type, or methanol, ethanol, formaldehyde, acetaldehyde, formic acid, and oxalic acid belonging to the organic type, preferably sulfur dioxide and iron powder.

[0058] Furthermore, in step S7, the Group IIA metal hydroxide emulsion is preferably calcium hydroxide emulsion, and the concentration of the Group IIA metal hydroxide emulsion is 1-20%, preferably 5-15%.

[0059] Calcium hydroxide emulsion (Ca(OH)2 is used as an example of alkali) is slowly added to the filtrate in two portions while stirring. The first portion is used to adjust the pH value to 7.5-8.0 for precipitation reaction. The precipitate is mainly CaF2. It is preferred to filter and separate the precipitate first. CaF2 can be sold as an industrial raw material, such as a metallurgical flux or a raw material for extracting fluorine. The second portion is used to slowly add calcium hydroxide emulsion, adjust the pH value to 9.5-10.0, and then carry out deep precipitation reaction. The main component of the precipitate is calcium hydrogen phosphate.

[0060] The reaction equations of the two precipitation reactions are as follows:

[0061] 2NaF + Ca(OH)2= CaF2 + 2NaOH,

[0062] Na2HPO4 + Ca(OH)2 = CaHPO4 + 2NaOH.

[0063] The solubility product of calcium fluoride CaF2 is Ksp = 3.9×10 -11 , PK=10.41. At pH 7.5~8.0, fluoride ions are in a dissociated state and only a small amount of calcium ions are needed to form calcium fluoride precipitation.

[0064] The dissociation of phosphate is divided into three steps, and the reaction equation is as follows:

[0065] ,

[0066] ,

[0067] .

[0068] When the pH value is 7.5-8.0, the solution is mainly composed of hydrogen phosphate, and the solubility product of calcium hydrogen phosphate CaHPO4 Ksp ≈ 1×10 -7 , which is much greater than the solubility product of calcium fluoride, so calcium fluoride precipitates first. When the pH value is in the range of 9.5-10.0, the calcium ion concentration is very low, and hydrogen phosphate begins to precipitate, with calcium hydrogen phosphate as the main precipitate.

[0069] Furthermore, in step S7, in the later stage of fluoride precipitation, PAM flocculant (1-2 mg / L) is preferably added to enhance the precipitation separation efficiency and further reduce the fluoride ion content in the filtrate.

[0070] Furthermore, after two filtration separations, the filtrate can be transported to a sewage treatment plant for deep treatment, or returned to step S1 to be used as spray liquid when the lithium battery is crushed, or to a circulating water pipeline for use in subsequent hydrometallurgical processes.

[0071] The total concentrations of fluoride ions and phosphates in the treated filtrate wastewater are controlled below 10 mg / L, respectively, meeting the third-level standard of the Integrated Wastewater Discharge Standard (GB8978-1996).

[0072] Compared with the prior art, the present invention has the following beneficial effects:

[0073] (1) When processing waste lithium-ion batteries, the catalytic effects of metal ions and alkalis after recycling and wet crushing will cause the solvent in the organic electrolyte to undergo various decomposition reactions or lipid exchange reactions. From a cost-effectiveness and cost perspective, it is not suitable to purify the waste lithium-ion batteries for the preparation of electrolytes. Instead, the best way to balance recovery efficiency and cost-effectiveness is to completely decompose and mineralize the waste lithium-ion batteries to produce carbon dioxide and inorganic salts.

[0074] (2) The shear-type one-time crushing method is used to minimize the generation of fine particles from the source and reduce the amount of fine particles entering the liquid phase, which is equivalent to simplifying the difficulty of subsequent liquid wastewater treatment.

[0075] (3) During the crushing process, the electrolyte and aqueous solution meet, which may trigger the reaction between the elemental lithium in the negative electrode and water, as well as the neutralization and decomposition reaction of the solvent in the electrolyte, causing the solution temperature to rise. By using alkaline solution spraying and full coverage to allow the flowing alkaline solution and electrolyte to be fully mixed, the water temperature rise during the hydrolysis process can be effectively prevented, avoiding the generation of excessive organic vapor to pollute the environment.

[0076] (4) The method of hydrolyzing the electrolyte with alkaline solution under the synergy of ultrasound can pre-hydrolyze and decompose cyclic ethylene carbonate, a substance with poor biodegradability, and solve the problem of low oxidation and decomposition efficiency when Fenton reagent oxidizes cyclic carbonate in the subsequent process.

[0077] (5) Ultrasonic wave assisted activation of H2O2 to produce hydroxyl radicals OH • The Fenton oxidation method can treat wastewater containing organic solvents, deeply oxidize linear carbonates, methanol, ethanol and other alcohol organics, realize the decomposition and mineralization of organic waste liquid, improve the biodegradability of wastewater, and make it meet the feed requirements of sewage treatment plants.

[0078] (6) The present invention adopts a relatively low energy consumption method to carry out low-cost and environmentally friendly treatment of waste lithium-ion battery electrolytes, which has significant advantages in cost input and environmental benefits. Compared with the pyrometallurgical recovery method, it greatly reduces the equipment investment and operating costs of the recovery production line. BRIEF DESCRIPTION OF THE DRAWINGS

[0079] Figure 1 It is a process flow chart of the present invention. DETAILED DESCRIPTION

[0080] The above contents of the present invention are further described in detail below through specific implementation modes in the form of embodiments, but the present invention is not limited thereto.

[0081] Example 1

[0082] The process flow chart of the present invention is as follows Figure 1 As shown. The raw materials used in this implementation are waste ternary lithium-ion aluminum shell batteries (the positive electrode material is 811 series). First, the alkaline solution spray switch is turned on, and the spray liquid is a 2% sodium hydroxide solution by mass. At a feed rate of 1.4 tons per hour, the waste lithium-ion batteries are fed into the upper feed port of the crusher via a feeding belt. The lithium battery material after crushing by the crusher is mixed with the alkaline solution and enters the hydrolysis tank below the crusher for hydrolysis under the synergy of ultrasound. The ultrasonic power intensity is 20W / cm 2 . The material is then fed into the hydrodynamic sorting equipment by a spiral conveyor pipe. Heavy materials such as pile heads and shells are sorted out along the spiral conveyor pipe at the bottom of the sorting machine; light materials such as diaphragms are sorted out along the spiral conveyor pipe above the sorting machine. The middle outlet is an aqueous phase containing a mixture of positive and negative electrode plates. The liquid-solid mass ratio during hydrolysis is 5:1. After sedimentation and separation, wastewater containing electrolyte is obtained. The wastewater enters the Fenton oxidation tank, and dilute phosphoric acid is added to adjust the pH value of the wastewater to 3.2. Ferrous sulfate heptahydrate powder is added first, and after thorough stirring and mixing, hydrogen peroxide is slowly added. The concentration of ferrous ions in the aqueous phase is 0.5mmol / L, and the molar ratio of hydrogen peroxide to ferrous ions is 2:1. The reaction is carried out for 2 hours under the synergy of ultrasound, and the ultrasonic power intensity is 50W / cm 2. Then, slowly add a 10% mass fraction of sodium carbonate solution to adjust the pH value to 5.5, heat the wastewater, introduce air to oxidize it to produce a precipitate, and filter and separate to obtain an iron hydroxide precipitate and a filtrate. Add 5% mass fraction of dilute phosphoric acid to the iron hydroxide solid phase to dissolve it, and then introduce sulfur dioxide gas to reduce all the iron ions in the solution to divalent iron ions. The divalent iron salt solution returns to step 4 as a Fenton agent. Add a 10% mass fraction of calcium hydroxide emulsion to the filtrate, slowly add and stir, first adjust the pH value of the filtrate to 7.5~8.0, and then add PAM flocculant at 1 mg / L to enhance precipitation to produce flocculent calcium fluoride precipitate, and then use a high-precision filter cloth (pore size ≤10μm) filter press to separate to obtain calcium fluoride precipitate, ensuring that the CaF2 retention rate is >95%. Calcium hydroxide emulsion with a mass fraction of 10% is added to the filtrate, and the pH value is adjusted to 9.5~10.0. The calcium hydrogen phosphate precipitate and filtrate are separated by filtration. Part of the filtrate is returned for alkali spraying and hydrolysis, and the rest is transported to the sewage treatment plant for further treatment.

[0083] After testing, the filtrate after two purification treatments had a fluoride ion content of 8.5 mmg / L, a total phosphate concentration of 5.0 mg / L, and a COD removal rate of 92.5%. 2+ Regeneration rate 95%.

[0084] Example 2

[0085] The raw materials used in this embodiment are lithium iron phosphate aluminum shell power batteries. First, the alkaline solution spray switch is turned on, and the spray liquid is a sodium hydroxide solution with a mass fraction of 2%. At a feeding rate of 0.7 tons per hour, the waste lithium-ion batteries are fed into the upper feed port of the crusher through the feeding belt. The lithium battery materials after crushing by the crusher are mixed with the alkaline solution and enter the hydrolysis tank below the crusher for hydrolysis under the synergy of ultrasound. The ultrasonic power intensity is 20W / cm 2 . The material is then fed into the hydrodynamic sorting equipment by a spiral conveyor pipe. Heavy materials such as pile heads and shells are sorted out along the spiral conveyor pipe at the bottom of the sorting machine; light materials such as diaphragms are sorted out along the spiral conveyor pipe at the top of the sorting machine. The middle outlet is an aqueous phase containing a mixture of positive and negative electrode plates, with a liquid-solid mass ratio of 6:1. After sedimentation and separation, wastewater containing electrolyte is obtained. The wastewater enters the Fenton oxidation tank, and dilute phosphoric acid is added to adjust the pH value of the wastewater to 3.0. Ferrous sulfate heptahydrate powder is added first, and after thorough stirring and mixing, hydrogen peroxide is slowly added. The concentration of ferrous ions in the aqueous phase is 0.5mmol / L, and the molar ratio of hydrogen peroxide to ferrous ions is 2:1. The reaction is carried out for 2 hours under the synergy of ultrasound, and the ultrasonic power intensity is 50W / cm 2. Then slowly add a 10% mass fraction of sodium carbonate solution to adjust the pH value to 5.5, heat the wastewater, introduce air to oxidize it to produce a precipitate, and filter and separate to obtain an iron hydroxide precipitate and a filtrate. Add 4% mass fraction of dilute phosphoric acid to the iron hydroxide solid phase to dissolve it, and then introduce sulfur dioxide gas to reduce all the iron ions in the solution to divalent iron ions. The divalent iron salt solution returns to step 4 as a Fenton agent. Add a 10% mass fraction of calcium hydroxide emulsion to the filtrate, slowly add and stir, adjust the pH value of the filtrate to 7.5~8.0, and then add PAM flocculant at 1 mg / L to enhance precipitation, produce flocculent calcium fluoride precipitate, and then use a high-precision filter cloth (pore size ≤10μm) centrifuge to separate the calcium fluoride precipitate, ensuring that the CaF2 retention rate is >95%. Calcium hydroxide emulsion with a mass fraction of 10% is added to the filtrate, and the pH value is adjusted to 9.5-10.0. The calcium hydrogen phosphate precipitate and the filtrate are separated by filtration. Part of the filtrate is returned for alkali spraying and hydrolysis, and the rest is transported to the sewage treatment plant for further treatment or to the subsequent hydrometallurgical process.

[0086] After testing, the filtrate after two purification treatments had a fluoride ion content of 8.2 mmg / L, a total phosphate concentration of 5.2 mg / L, and a COD removal rate of 92.6%. 2+ Regeneration rate 95%.

[0087] Example 3

[0088] In this example, the raw material used is waste ternary lithium-ion soft-pack batteries (the positive electrode material is 523 series). First, activate the alkaline solution spray switch, and the spray liquid is a 2% sodium hydroxide solution. At a feed rate of 1.4 tons per hour, the waste lithium-ion batteries are fed into the upper feed port of the crusher via a feeding belt. The crushed lithium battery material is mixed with the alkaline solution and enters the hydrolysis tank below the crusher. Hydrolysis is carried out for 30 minutes under ultrasonic assisted conditions, with an ultrasonic power intensity of 20W / cm 2 . The material is then fed into the hydrodynamic sorting equipment by a spiral conveyor pipe. Heavy materials such as pile heads and shells are sorted out along the spiral conveyor pipe at the bottom of the sorting machine; light materials such as diaphragms are sorted out along the spiral conveyor pipe at the top of the sorting machine. The middle outlet is an aqueous phase containing a mixture of positive and negative electrode plates, with a liquid-solid mass ratio of 5:1. After sedimentation and separation, wastewater containing electrolyte is obtained. The wastewater enters the Fenton oxidation tank, and dilute phosphoric acid is added to adjust the pH value of the wastewater to 3.2. Ferrous sulfate heptahydrate powder is added first, and after thorough stirring and mixing, hydrogen peroxide is slowly added. The concentration of ferrous ions in the aqueous phase is 0.5mmol / L, and the molar ratio of hydrogen peroxide to ferrous ions is 2:1. The reaction is carried out for 2 hours under the synergy of ultrasound, and the ultrasonic power intensity is 50W / cm 2. Then slowly add a 10% mass fraction of sodium carbonate solution to adjust the pH value to 5.5, heat the wastewater, introduce air to oxidize it to produce a precipitate, and filter and separate to obtain an iron hydroxide precipitate and a filtrate. Add 5% mass fraction of dilute phosphoric acid to the iron hydroxide solid phase to dissolve it, and then introduce sulfur dioxide gas to oxidize all the iron ions in the solution into divalent iron ions. The divalent iron salt solution returns to step 4 as a Fenton agent. Add a 10% mass fraction of calcium hydroxide emulsion to the filtrate, slowly add and stir, adjust the pH value of the filtrate to 7.5~8.0, and then add PAM flocculant at 1 mg / L to enhance precipitation, produce flocculent calcium fluoride precipitate, and then use a high-precision filter cloth (pore size ≤10μm) centrifuge to separate the calcium fluoride precipitate, ensuring that the CaF2 retention rate is >95%. Calcium hydroxide emulsion with a mass fraction of 10% is added to the separated filtrate, and the pH value is adjusted to 9.5~10.0. The calcium hydrogen phosphate precipitate and filtrate are obtained by filtration and separation. Part of the filtrate is returned for alkali spraying and hydrolysis, and the rest is transported to the sewage treatment plant for further treatment.

[0089] After testing, the filtrate after two purification treatments had a fluoride ion content of 8.2 mmg / L, a total phosphate concentration of 5.0 mg / / L, a COD removal rate of 93.0%, and Fe 2+ Regeneration rate 95%.

Claims

1. A method for treating electrolyte after wet crushing of waste lithium-ion batteries, characterized in that: The following steps are involved: S1. Charged crushing and alkali solution spray coverage: Several rows of spray ports are set above the crusher shear port. When shearing the charged waste lithium-ion batteries, an alkali metal hydroxide solution is sprayed simultaneously to completely cover the crushed material with the alkali metal hydroxide solution. The size of the crushed material is 5-45mm. S2 ultrasonic synergistic hydrolysis: The crushed material obtained in step S1 is mixed with an alkali metal hydroxide solution into a hydrolysis tank, and the hydrolysis reaction is carried out under ultrasonic and stirring conditions with a power intensity of 5-40W / cm² to decompose the carbonate organic matter in the electrolyte; S3. Hydrodynamic separation: The hydrolyzed material from step S2 is separated by a hydrodynamic separation device to separate a heavy component including the shell and pile head, a medium component including the electrode mixture, and a light component including the diaphragm. The electrolyte-containing wastewater generated during the separation process is collected, including centrifugal filtrates and washing wastewater from the low, medium, and high outlets of the separator. S4. Fenton oxidation degradation: Add dilute acid to the wastewater obtained in step S3 to adjust the pH value to 2.5-5.0, add 0.2mmol / L-1mol / L divalent iron salt solution, and then press hydrogen peroxide and Fe 2+ Hydrogen peroxide is added in a molar ratio of 1-3:1, and a Fenton oxidation reaction is carried out in an oxidation reactor under the synergy of ultrasonic waves with a power intensity of 50-100W / cm² at a reaction temperature of 20-35°C; S5 precipitation separation: after the Fenton reaction in step S4, an alkali metal salt solution was added to the wastewater to adjust the pH value to 4.5-6.0, the wastewater was heated, air was introduced to oxidize the precipitate, and the precipitate was filtered to obtain iron hydroxide and the filtrate; S6. Regeneration of ferrous salt: adding dilute acid to dissolve the ferric hydroxide precipitate obtained in step S5, and then adding a reducing agent to react to obtain a ferrous salt solution, and returning the cycle to step S4; S7. Fluoride and phosphorus are precipitated in steps: Under stirring, a Group IIA metal hydroxide emulsion is added to the filtrate obtained in step S5, and the pH value is adjusted twice. The first step is to adjust the pH to 6.0-8.0 to precipitate fluoride, and the precipitate and the filtrate are separated by filtration; the second step is to adjust the pH to 8.0-10.0 to precipitate hydrogen phosphate; and the precipitate and the filtrate are separated by filtration.

2. The method for treating electrolyte after wet crushing of waste lithium-ion batteries according to claim 1, characterized in that: The spray ports are arranged in 1-8 rows, the length of each row of spray ports is greater than the length of the shear port, and the total width of the spray row is greater than the width of the shear port. The total length and width of the spray row ensure that the sprayed alkaline solution can fully cover the crushed material; the crusher shear port is located above the hydrolysis tank.

3. The method for treating electrolyte after wet crushing of waste lithium-ion batteries according to claim 1, wherein: In steps S1 and S2, the mass fraction of the alkali metal hydroxide solution is 0.05%-30%.

4. The method for treating electrolyte after wet crushing of waste lithium-ion batteries according to claim 1, characterized in that: In step S4, the dilute acid is at least one of phosphoric acid, sulfuric acid, nitric acid, hydrochloric acid, formic acid, acetic acid, oxalic acid, malonic acid, lactic acid, and tartaric acid.

5. The method for treating electrolyte after wet crushing of waste lithium-ion batteries according to claim 1, characterized in that: In step S2, ultrasonic vibration plates are arranged on both sides of the hydrolysis tank; in step S4, ultrasonic vibration plates are distributed around the oxidation reactor.

6. The method for treating electrolyte after wet crushing of waste lithium-ion batteries according to claim 1, characterized in that: In step S5, the alkali metal salt is an alkali metal carbonate, and the concentration of the alkali metal carbonate solution is 0.5% to 20%.

7. The method for treating electrolyte after wet crushing of waste lithium-ion batteries according to claim 1, characterized in that: In step S6, the dilute acid is at least one of phosphoric acid, sulfuric acid, nitric acid and hydrochloric acid.

8. The method for treating electrolyte after wet crushing of waste lithium-ion batteries according to claim 1, characterized in that: In step S6, the reducing agent is at least one of sulfur dioxide, carbon monoxide, iron powder, sodium sulfite, sodium dithionite, methanol, ethanol, formaldehyde, acetaldehyde, formic acid, and oxalic acid.

9. The method for treating electrolyte after wet crushing of waste lithium-ion batteries according to claim 1, characterized in that: In step S7, the mass fraction of the Group IIA metal hydroxide emulsion is 1-20%.

10. The method for treating electrolyte after wet crushing of waste lithium-ion batteries according to claim 1, characterized in that: In step S7, after the fluoride is precipitated, 1-2 mg / L of PAM flocculant is added to enhance precipitation separation.

Images