Method for recycling underwater crushing wastewater of retired lithium battery

Abstract

The invention belongs to the technical field of waste battery recycling treatment, and particularly relates to a method for recycling waste water generated by underwater crushing of a decommissioned lithium battery, which comprises the following steps: (1) adding a demulsifier into waste water generated by underwater crushing of the decommissioned lithium battery, mixing, and performing ultrasonic liquid separation to obtain an electrolyte phase and a water phase; (2) adding a flocculant into the water phase prepared in the step (1), mixing, standing for flocculation, and filtering to obtain a filter cake and first filtrate; (3) adding a lithium hydroxide solution into the first filtrate prepared in the step (2) to adjust the pH value to 2-5, precipitating excessive iron ions, and filtering to obtain a second filtrate; and (4) heating the second filtrate prepared in the step (3), adding a carbonate solution to adjust the pH value to be alkaline, standing, filtering to obtain a lithium carbonate precipitate and a third filtrate, washing the lithium carbonate precipitate to obtain crude lithium carbonate, and recycling the third filtrate as the water for the underwater crushing process of the retired lithium battery.

Description

Technical Field

[0001] The invention belongs to the technical field of waste battery recycling and treatment, and in particular relates to a method for recycling waste water from underwater crushing of retired lithium batteries. Background Art

[0002] At present, in the recycling technology of retired lithium batteries, nitrogen or underwater environment is often used to isolate oxygen because fire and explosion may occur during the crushing process. Among them, nitrogen protection has more and more mature application cases in the industry. However, the underwater environment can not only isolate the air, but also take away the heat generated by the instantaneous crushing process, and avoid the safety risk of fire caused by self-produced oxygen during the crushing of retired batteries in a nitrogen environment. Therefore, more and more related technologies for underwater crushing are being researched and developed. The biggest problem in this technology is the treatment and recycling of wastewater.

[0003] During the underwater crushing process, the active lithium, inorganic electrolytes, and organic solvents in the retired lithium batteries will enter the water. Active lithium is generally present in the negative electrode, and after entering the water, it reacts with water to convert into lithium ions; the inorganic electrolyte is mainly lithium hexafluorophosphate, which reacts with water to convert into fluoride ions, phosphates, and polyfluorolithium phosphate after entering the water; and the organic solvents in the waste electrolyte are mainly carbonates, which can be divided into water-insoluble chain carbonates and water-soluble cyclic carbonates. Soluble carbonates act as emulsifiers, and the water body can exist stably. In addition, some black powder particles will enter the water during the crushing process, and some fluoride ions will also produce precipitation with lithium ions. The relevant reactions are as follows:

[0004] Reaction of active lithium and water: 2Li+2H2O→2LiOH+H2↑

[0005] Lithium hexafluorophosphate reacts with water: LiPF6+2H2O→LiPF2O2+4HF

[0006] Lithium hexafluorophosphate reacts with water: LiPF6+6H2O→Li2PO3F+H2PO3F+4HF

[0007] Fluoride ions react with lithium ions: F - +Li + →LiF↓

[0008] Therefore, the wastewater generated by the underwater crushing of retired lithium batteries has complex water quality, containing black powder particles, high COD, and high-value elements lithium and fluorine, which makes it difficult to treat and recycle. The main problems are concentrated on: ① Because soluble carbonates act as emulsifiers, water bodies can exist stably with high COD properties, making it difficult to remove organic carbonates by stratification and liquid separation; ② The water contains phosphate ions and lithium ions, which will form tiny lithium phosphate crystals, causing the filter pores to be blocked, making it very difficult to filter, greatly increasing the difficulty of solid-liquid separation.

[0009] Therefore, there is an urgent need to design a fast, efficient and low-cost process for recycling wastewater from underwater crushing of retired lithium batteries. Summary of the invention

[0010] The present invention aims to solve at least one of the technical problems existing in the related art. To this end, the present invention proposes a method for recycling wastewater from underwater crushing of retired lithium batteries, which can quickly, efficiently and at a low cost recycle wastewater from underwater crushing of retired lithium batteries.

[0011] The above technical objectives of the present invention are achieved through the following technical solutions:

[0012] A method for recycling wastewater from underwater crushing of retired lithium batteries, comprising the following steps: (1) adding a demulsifier to the wastewater generated by underwater crushing of retired lithium batteries, mixing and then ultrasonically separating the liquids to obtain an electrolyte phase and an aqueous phase, wherein the demulsifier is a mixture of a demulsifier A and a demulsifier B, wherein the demulsifier A is at least one of didecyldimethylammonium chloride and tetradecyltrimethylammonium chloride, and the demulsifier B is at least one of triethylamine, ethanolamine and isopropanolamine; (2) adding flocculants to the aqueous phase obtained in step (1); After the coagulant is mixed, it is allowed to stand for flocculation, and filtered to obtain a filter cake and a first filtrate; (3) lithium hydroxide solution is added to the first filtrate obtained in step (2) to adjust the pH to 2-5, and after the excess iron ions are precipitated, the second filtrate is obtained by filtering; (4) the second filtrate obtained in step (3) is heated and a carbonate solution is added to adjust the pH to alkaline, and the mixture is allowed to stand for filtering to obtain a lithium carbonate precipitate and a third filtrate, and the lithium carbonate precipitate is washed to obtain crude lithium carbonate, and the third filtrate is reused as water for the underwater crushing process of retired lithium batteries.

[0013] In one embodiment, in step (1), the mass proportion of the demulsifier A in the demulsifier is 20%-40%, and the mass proportion of the demulsifier B in the demulsifier is 60%-80%.

[0014] In one embodiment, in step (1), the demulsifier is added at 0.05%-0.3% of the mass of the wastewater.

[0015] In one embodiment, in step (1), the demulsifier is added at 0.01%-0.25% of the mass of the wastewater.

[0016] In one embodiment, in step (1), the demulsifier is added dropwise.

[0017] In one embodiment, in step (1), the demulsifier is added and stirred for 5-20 minutes.

[0018] In one embodiment, in step (1), the demulsifier is added and stirred for 10-15 minutes.

[0019] In one embodiment, in step (2), the flocculant is a polyferric sulfate solution with a mass concentration of 20%-40%.

[0020] In one embodiment, in step (2), the flocculant is a polyferric sulfate solution with a mass concentration of 25%-35%.

[0021] In one embodiment, in step (2), the flocculant is added at 2%-5% of the mass of the aqueous phase.

[0022] In one embodiment, in step (2), the flocculant is added at 3%-4% of the mass of the aqueous phase.

[0023] In one embodiment, in step (2), after adding the flocculant, the mixture is allowed to stand for 5-20 minutes before filtering.

[0024] In one embodiment, in step (2), after adding the flocculant, the mixture is allowed to stand for 8-15 minutes before filtering.

[0025] In one embodiment, in step (2), the filter cake obtained is a mixture of battery powder, lithium fluoride and a small amount of iron phosphate and polyferric sulfate, which can be used as a raw material for leaching recovery treatment.

[0026] In one embodiment, in step (3), the mass concentration of the lithium hydroxide solution is 5%-15%.

[0027] In one embodiment, in step (3), the mass concentration of the lithium hydroxide solution is 8%-12%.

[0028] In one embodiment, in step (4), the heating is to raise the temperature of the second filtrate to 30-50°C.

[0029] In one embodiment, in step (4), the heating is to raise the temperature of the second filtrate to 35-45°C.

[0030] In one embodiment, in step (4), the carbonate solution is a sodium carbonate or potassium carbonate solution with a mass concentration of 10%-30%.

[0031] In one embodiment, in step (4), the carbonate solution is a sodium carbonate or potassium carbonate solution with a mass concentration of 15%-25%.

[0032] In one embodiment, in step (4), adjusting the pH to be alkaline means adjusting the pH to 7-10.

[0033] In one embodiment, in step (4), adjusting the pH to be alkaline means adjusting the pH to 7.5-9.

[0034] In one embodiment, the wastewater generated by the underwater crushing of retired lithium batteries in step (1) comes from the crushing process of retired lithium battery monomers, and the crushing process of retired lithium battery monomers includes the following steps: immersing the retired lithium battery monomers with voltage in water for crushing or shredding, and after crushing, soaking under the water surface to fish out the battery crushed materials with a screen, drying the wet battery crushed materials and crushing and sorting them to obtain battery powder, copper material, aluminum material, and diaphragm, and the rest is the wastewater generated by the underwater crushing of retired lithium batteries. The mass ratio of retired lithium battery monomers to water is: 1: (1-2), the soaking time is 10-60min, and the mesh number of the screen is 3-10 meshes.

[0035] The beneficial effects of the present invention are:

[0036] (1) The present invention develops a targeted demulsifier formula, uses a demulsification process to treat organic wastewater containing electrolyte solvents, efficiently separates the electrolyte organic solvent components in the wastewater, and reduces the COD index in the water;

[0037] (2) The present invention uses a flocculation process of adding a flocculant to recover the battery powder and lithium fluoride in the wastewater, which not only recovers the battery powder and lithium fluoride in the wastewater, but also precipitates the phosphate in the water, greatly improving the filtering performance;

[0038] (3) The present invention uses a demulsification-flocculation-lithium precipitation process to treat the underwater crushing wastewater of retired lithium batteries, recover the high-value element lithium in the water, and produce crude lithium carbonate. The treated wastewater is reused in the underwater crushing process, and the water circulation forms a closed loop, and no additional wastewater is generated. Theoretically, 100% of the lithium element is recovered;

[0039] (4) The demulsification-flocculation-lithium precipitation process adopted in the present invention can be applied not only to the treatment of underwater crushing wastewater of retired lithium batteries, but also to the pretreatment of all wastewater containing carbonate electrolytes, providing a solution to the problem of organic pollution of electrolytes. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a schematic diagram of the process of Example 1 of the present invention. DETAILED DESCRIPTION

[0041] The present invention will be further described below in conjunction with specific embodiments.

[0042] Embodiment 1:

[0043] A method for recycling wastewater from underwater crushing of retired lithium batteries, such as Figure 1 As shown, the following steps are included:

[0044] (1) 50 kg of retired lithium iron phosphate power battery cells with voltage are immersed in 50 L of water below the surface for crushing or shredding in batches. The crushed materials are soaked under the water surface for more than 10 minutes and then the battery crushed materials are fished out with a 5-mesh sieve. The wet battery crushed materials are dried and crushed to obtain battery powder, copper material, aluminum material, and diaphragm. The rest is the wastewater generated by underwater crushing of retired lithium batteries;

[0045] (2) Tetradecyltrimethylammonium chloride and isopropanolamine are mixed evenly to prepare a demulsifier, wherein the mass proportion of tetradecyltrimethylammonium chloride in the demulsifier is 20%, and the mass proportion of isopropanolamine in the demulsifier is 80%. The demulsifier is added dropwise to the wastewater generated by underwater crushing of retired lithium batteries, and the amount of the demulsifier added is 0.1% of the mass of the wastewater. After the addition is completed, the mixture is stirred for 10 minutes until it is uniform;

[0046] (3) After the demulsifier is added, the mixed liquid is allowed to stand for a while, and then ultrasound forms a clear stratification boundary. The electrolyte phase and the water phase are separated by a liquid separation device and a liquid separation box to obtain electrolyte organic matter as a raw material for recycling the electrolyte organic phase;

[0047] (4) adding 4% of the mass of the aqueous phase to the aqueous phase after separation of the electrolyte for flocculation, wherein the flocculant is a polyferric sulfate solution with a mass concentration of 30%, stirring evenly, standing for 10 minutes, and then filtering to obtain a filter cake and a filtrate. The filter cake is mainly a mixture of battery powder, lithium fluoride, and a small amount of iron phosphate and polyferric sulfate. The filter cake is used as a raw material for rear-end leaching to further recover valuable metal elements;

[0048] (5) adding 10% lithium hydroxide solution to the filtrate to adjust the pH to 3, precipitating excess iron ions, and filtering to obtain a lithium-containing filtrate;

[0049] (6) The lithium-containing filtrate is heated to 35° C. and 20% sodium carbonate solution is added until the solution pH reaches 8. The solution is allowed to stand to obtain lithium carbonate precipitate, which is filtered and washed with pure water to obtain crude lithium carbonate. The filtered filtrate is used as recycled water for underwater crushing of retired lithium batteries, thus achieving complete recycling of water. Due to the recycling of wastewater, the entire system has no external discharge, and the recovery rate of lithium ions can reach 100%.

[0050] The water quality of the wastewater generated by underwater crushing of retired lithium batteries in Example 1 and the recycled water generated in step (6) is shown in Table 1, and the elemental composition of the filter cake generated in step (4) is shown in Table 2.

[0051] Table 1. Water quality of wastewater and recycled water

[0052] Li(mg / L) F(mg / L) P (mg / L) COD(mg / L) Wastewater quality 1050 140 2800 78000 Circulating water quality 23 56 5 10000

[0053] Table 2. Element composition of filter cake

[0054] Li(%) F(％) P(％) C(％) Moisture content (%) Filter cake components 0.9 2 4 20 25％

[0055] Embodiment 2:

[0056] A method for recycling wastewater from underwater crushing of retired lithium batteries, which is different from Example 1 only in that the demulsifier in this embodiment is prepared by uniformly mixing didecyldimethylammonium chloride and isopropanolamine, the mass proportion of didecyldimethylammonium chloride in the demulsifier is 20%, the mass proportion of isopropanolamine in the demulsifier is 80%, and the other conditions are the same as those in Example 1.

[0057] Embodiment 3:

[0058] A method for recycling wastewater from underwater crushing of retired lithium batteries, which is different from Example 1 only in that the demulsifier in this embodiment is prepared by uniformly mixing tetradecyltrimethylammonium chloride and triethylamine, the mass proportion of tetradecyltrimethylammonium chloride in the demulsifier is 20%, the mass proportion of triethylamine in the demulsifier is 80%, and the other conditions are the same as Example 1.

[0059] Embodiment 4:

[0060] A method for recycling wastewater from underwater crushing of retired lithium batteries, which is different from Example 1 only in that the demulsifier in this embodiment is prepared by uniformly mixing didecyldimethylammonium chloride and triethylamine, the mass proportion of didecyldimethylammonium chloride in the demulsifier is 20%, the mass proportion of triethylamine in the demulsifier is 80%, and the other conditions are the same as Example 1.

[0061] Embodiment 5:

[0062] A method for recycling wastewater from underwater crushing of retired lithium batteries, which is different from Example 1 only in that the demulsifier in this embodiment is prepared by uniformly mixing tetradecyltrimethylammonium chloride and ethanolamine, the mass proportion of tetradecyltrimethylammonium chloride in the demulsifier is 20%, the mass proportion of ethanolamine in the demulsifier is 80%, and the other conditions are the same as Example 1.

[0063] Embodiment 6:

[0064] A method for recycling wastewater from underwater crushing of retired lithium batteries, which is different from Example 1 only in that the demulsifier in this embodiment is prepared by uniformly mixing didecyldimethylammonium chloride and ethanolamine, the mass proportion of didecyldimethylammonium chloride in the demulsifier is 20%, the mass proportion of ethanolamine in the demulsifier is 80%, and the other conditions are the same as Example 1.

[0065] Comparative Example 1:

[0066] A method for recycling wastewater from underwater crushing of retired lithium batteries, which differs from Example 1 only in that the demulsifier in step (2) of Example 1 is not added in this comparative example, and the other conditions are the same as those in Example 1.

[0067] Table 3. Water quality of wastewater and recycled water in Comparative Example 1

[0068] Li(mg / L) F(mg / L) P (mg / L) COD(mg / L) Wastewater quality 1050 140 2800 78000 Circulating water quality 20 42 5 77400

[0069] Table 4. Element composition of filter cake of comparative example 1

[0070] Li(%) F(％) P(％) C(％) Moisture content (%) Filter cake components 0.8 1.9 3.8 19.1 27％

[0071] Comparative Example 2:

[0072] A method for recycling wastewater from underwater crushing of retired lithium batteries is different from Example 1 only in that the demulsifier in this comparative example is a single didecyldimethylammonium chloride, and the other conditions are the same as those in Example 1.

[0073] Comparative Example 3:

[0074] A method for recycling wastewater from underwater crushing of retired lithium batteries is disclosed. The method is different from Example 1 only in that no flocculant is added for flocculation in step (4) of this comparative example, and the other conditions are the same as those in Example 1. As a result, in step (4), the filtering effect is poor and the filter cloth is clogged.

[0075] Comparative Example 4:

[0076] A method for recycling wastewater from underwater crushing of retired lithium batteries is disclosed, which differs from Example 1 only in that ethanol is used instead of tetradecyltrimethylammonium chloride in this comparative example, and the other conditions are the same as those in Example 1.

[0077] Table 5. Water quality of wastewater and recycled water in Comparative Example 4

[0078] Li(mg / L) F(mg / L) P (mg / L) COD(mg / L) Wastewater quality 1050 140 2800 78000 Circulating water quality 38 52 4 79000

[0079] Table 6. Element composition of filter cake of comparative example 4

[0080] Li(%) F(％) P(％) C(％) Moisture content (%) Filter cake components 0.8 1.9 3.8 19.1 26％

[0081] The demulsification performance of Examples 1-6 and Comparative Examples 1-2 and 4 was tested, and the data in Table 7 were obtained. The flocculation and filtration performance of Examples 1-2 and Comparative Example 3 was tested, and the data in Table 8 were obtained.

[0082] Table 7. Demulsification performance test

[0083]

[0084]

[0085] Table 8. Flocculation and filtration performance test

[0086]

[0087] From Examples 1-6 in Table 7, it can be seen that the demulsifier prepared with two surfactants has a better demulsification effect. The oil-liquid two-phase stratification can be achieved after a short period of standing, the oil-water interface is clear, and the removed electrolyte contains about 10% water. By comparing Example 1 with Comparative Example 1, it can be seen that without adding a demulsifier, the electrolyte is difficult to stratify, and there is no stratification after standing for 1 hour; By comparing Example 1 with Comparative Example 4, it can be seen that without adding the specific demulsifier of the present invention, the electrolyte is difficult to stratify, and there is no stratification after standing for 1 hour; By comparing Example 1 with Comparative Example 2, it can be seen that the effect of adding only one surfactant is poor. From Table 8, it can be seen that the filtration effect is poor when the flocculant of the present invention is not added, and the filter cake is difficult to form.

Claims

1. A method for recycling wastewater from underwater crushing of retired lithium batteries, characterized in that: The following steps are involved: (1) adding a demulsifier to wastewater generated by underwater crushing of retired lithium batteries, mixing and then ultrasonically separating the wastewater to obtain an electrolyte phase and an aqueous phase, wherein the demulsifier is a mixture of a demulsifier A and a demulsifier B, wherein the demulsifier A is at least one of didecyldimethylammonium chloride and tetradecyltrimethylammonium chloride, and the demulsifier B is at least one of triethylamine, ethanolamine and isopropanolamine; (2) adding a flocculant to the aqueous phase obtained in step (1), mixing the mixture, standing the mixture for flocculation, and filtering the mixture to obtain a filter cake and a first filtrate; (3) adding lithium hydroxide solution to the first filtrate obtained in step (2) to adjust the pH to 2-5, precipitating excess iron ions, and filtering to obtain a second filtrate; (4) The second filtrate obtained in step (3) is heated and then a carbonate solution is added to adjust the pH to alkaline. After standing, the second filtrate is filtered to obtain a lithium carbonate precipitate and a third filtrate. The lithium carbonate precipitate is washed to obtain crude lithium carbonate. The third filtrate is reused as water for the underwater crushing process of retired lithium batteries.

2. The method for recycling wastewater from underwater crushing of retired lithium batteries according to claim 1 is characterized in that: In step (1), the mass proportion of the demulsifier A in the demulsifier is 20%-40%, and the mass proportion of the demulsifier B in the demulsifier is 60%-80%.

3. The method for recycling wastewater from underwater crushing of retired lithium batteries according to claim 1 is characterized in that: In step (1), the demulsifier is added at 0.05%-0.3% of the mass of the wastewater.

4. The method for recycling wastewater from underwater crushing of retired lithium batteries according to claim 1 is characterized in that: In step (2), the flocculant is a polyferric sulfate solution with a mass concentration of 20%-40%.

5. The method for recycling wastewater from underwater crushing of retired lithium batteries according to claim 1 is characterized in that: In step (2), the flocculant is added at 2%-5% of the mass of the aqueous phase.

6. The method for recycling wastewater from underwater crushing of retired lithium batteries according to claim 1 is characterized in that: In step (3), the mass concentration of the lithium hydroxide solution is 5%-15%.

7. The method for recycling wastewater from underwater crushing of retired lithium batteries according to claim 1 is characterized by: In step (4), the heating is to raise the temperature of the second filtrate to 30-50°C.

8. The method for recycling wastewater from underwater crushing of retired lithium batteries according to claim 1 is characterized by: In step (4), the carbonate solution is a sodium carbonate or potassium carbonate solution with a mass concentration of 10%-30%.

9. The method for recycling wastewater from underwater crushing of retired lithium batteries according to claim 1 is characterized in that: In step (4), adjusting the pH to be alkaline means adjusting the pH to 7-10.

10. The method for recycling wastewater from underwater crushing of retired lithium batteries according to claim 1, characterized in that: The wastewater generated by the underwater crushing of retired lithium batteries in step (1) comes from the crushing process of retired lithium battery monomers. The method comprises the following steps: immersing the retired lithium battery cells with voltage into water for crushing or shredding, soaking the crushed battery cells under the water surface and then scooping out the battery crushed materials with a sieve, drying the wet battery crushed materials and crushing and sorting them to obtain battery powder, copper materials, aluminum materials and diaphragms, and the rest is the wastewater generated by the underwater crushing of retired lithium batteries.

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