Method for recycling wastewater of underwater crushing of retired lithium battery

Abstract

The application belongs to the technical field of waste battery recycling and processing, and particularly relates to a method for recycling wastewater generated in underwater crushing of retired lithium batteries, comprising the following steps: (1) adding a demulsifier to the wastewater generated in underwater crushing of the retired lithium batteries, and then performing ultrasonic separation to obtain an electrolyte phase and an aqueous phase; (2) adding a flocculating agent to the aqueous phase obtained in step (1), and then performing static flocculation to obtain a filter cake and a first filtrate; (3) adding a lithium hydroxide solution to the first filtrate obtained in step (2) to adjust the pH to 2-5, and then performing filtration to obtain a second filtrate after precipitating excess iron ions; (4) adding a carbonate solution to the second filtrate obtained in step (3) to adjust the pH to alkaline after heating, and then performing filtration to obtain lithium carbonate precipitate and a third filtrate, and then washing the lithium carbonate precipitate to obtain crude lithium carbonate, and the third filtrate is recycled to water used in the underwater crushing process of the retired lithium batteries.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of waste battery recycling and processing, and particularly relates to a method for recycling wastewater generated in underwater crushing of retired lithium batteries. BACKGROUND

[0002] Currently, in the recycling technology of retired lithium batteries, fire and explosion may occur during the crushing process, and nitrogen or underwater environment is often used to isolate oxygen. Nitrogen protection is more mature in the industry, but underwater environment not only isolates air, but also carries away the heat generated in the instant crushing process, and can avoid the safety risk of fire caused by self-produced oxygen during the crushing process of retired batteries in a nitrogen environment. Therefore, the related technology of underwater crushing is being researched and developed more and more, and the biggest problem in this technology is the treatment and recycling of wastewater.

[0003] In the underwater crushing process, active lithium, inorganic electrolyte and waste electrolyte organic solvent in the retired lithium battery will enter the water. Active lithium generally exists in the negative electrode and is converted into lithium ions after reacting with water; the inorganic electrolyte is mainly lithium hexafluorophosphate, which is converted into fluoride ions, phosphate ions and polyfluorophosphate lithium after reacting with water; and the main component of the waste electrolyte organic solvent is carbonate, which can be divided into water-insoluble chain carbonates and water-soluble cyclic carbonates. The soluble carbonates act as emulsifiers, and the water body can exist stably. In addition, part of the black powder particles will also enter the water during the crushing process, and part of the fluoride ions will also produce precipitates with lithium ions. The related reactions are as follows:

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

[0005] Reaction of lithium hexafluorophosphate and water: LiPF6 + 2H2O → LiPF2O2 + 4HF

[0006] Reaction of lithium hexafluorophosphate and water: LiPF6 + 6H2O → Li2PO3F + H2PO3F + 4HF

[0007] Reaction of fluoride ions and lithium ions: F - + Li + → LiF↓

[0008] Therefore, the wastewater generated in the underwater crushing of retired lithium batteries has a complex water quality, contains black powder particles, has high COD and has the characteristics of high-value elements lithium and fluorine, and the treatment and recycling are difficult. The main problems are: ① Because the soluble carbonates act as emulsifiers, the water body can exist stably with high COD, making it difficult to remove the organic carbonates by layering and liquid separation; ② The water contains phosphate ions and lithium ions, which will form micro lithium phosphate crystals, making it very difficult to filter and greatly increasing the difficulty of solid-liquid separation.

[0009] Therefore, it is urgent to design a fast, efficient and low-cost process method for recycling waste water from underwater crushing of retired lithium batteries. SUMMARY

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

[0011] The above technical purpose of the present application is achieved by the following technical scheme:

[0012] A method for recycling waste water from underwater crushing of retired lithium batteries, comprising the following steps: (1) adding a demulsifier to the waste water generated by underwater crushing of retired lithium batteries, mixing and then performing ultrasonic separation to obtain an electrolyte phase and an aqueous phase, wherein the demulsifier is a mixture of demulsifier A and demulsifier B, 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 flocculating agent to the aqueous phase obtained in step (1) and mixing, then standing and flocculating, and filtering 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 then filtering to obtain a second filtrate; (4) heating the second filtrate obtained in step (3), adding a carbonate solution to adjust the pH to alkaline, standing and then 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 water for the underwater crushing process of retired lithium batteries.

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

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

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

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

[0017] In an embodiment, in step (1), after adding the demulsifier, stirring is performed for 5-20 min.

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

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

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

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

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

[0023] In an embodiment, in step (2), the flocculant is added and allowed to stand for 5-20 minutes before filtering.

[0024] In an embodiment, in step (2), the flocculant is added and allowed to stand for 8-15 minutes before filtering.

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

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

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

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

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

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

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

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

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

[0034] In an embodiment, the wastewater generated by underwater crushing of the retired lithium battery in step (1) is derived from a retired lithium battery monomer crushing process, which comprises the following steps: immersing the retired lithium battery monomer with voltage into water for crushing or shredding, after crushing, soaking under the water surface, and then using a screen to fish out the battery crushing material, drying the wet battery crushing material, and then crushing and sorting to obtain battery powder, copper material, aluminum material, and separator, and the remaining is the wastewater generated by underwater crushing of the retired lithium battery. The mass ratio of the retired lithium battery monomer to water is 1:(1-2), the soaking time is 10-60 min, and the mesh number of the screen is 3-10 meshes.

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

[0036] (1) The present application 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 application uses a flocculation process by adding a flocculant to recover and treat the battery powder and lithium fluoride in the wastewater, not only recovers the battery powder and lithium fluoride in the wastewater, but also precipitates the phosphate in the water, greatly improving the filtration performance;

[0038] (3) The present application uses a demulsification-flocculation-lithium precipitation process to treat the wastewater generated by underwater crushing of the retired lithium battery, recovers the high-value element lithium in the water, and produces crude lithium carbonate, and the treated wastewater is reused in the underwater crushing process to form a closed loop, without additional external wastewater, and the lithium element is theoretically 100% recovered;

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

[0040] Figure 1 The flowchart of Example 1 of the present application is shown. DETAILED DESCRIPTION

[0041] The present application will be further described below in conjunction with specific examples.

[0042] Example 1:

[0043] A method for recycling wastewater generated by underwater crushing of retired lithium batteries, as shown in Figure 1 , comprising the following steps:

[0044] (1) Batch 50 kg of retired lithium iron phosphate power battery monomer with voltage into the water below the water surface containing 50 L water for crushing or shredding, the broken material after soaking in water for more than 10 min, the battery crushing material is fished out with 5 mesh screen, the wet battery crushing material is dried and then crushed and sorted to get battery powder, copper material, aluminum material, separator, and the rest is the wastewater produced by underwater crushing of retired lithium batteries;

[0045] (2) Take tetradecyl trimethyl ammonium chloride and isopropanol amine and mix evenly to prepare a demulsifier, the mass fraction of tetradecyl trimethyl ammonium chloride in the demulsifier is 20%, and the mass fraction of isopropanol amine in the demulsifier is 80%, drop the demulsifier into the wastewater produced by underwater crushing of retired lithium batteries, the drop amount of the demulsifier is 0.1% of the mass of the wastewater, and after the drop is completed, stir for 10 min to make it uniform;

[0046] (3) After the mixed solution after adding the demulsifier is placed, ultrasonic is formed to form an obvious layered boundary, and then the electrolyte phase and the water phase are separated by a liquid separation device tank to obtain electrolyte organic matter as a raw material for electrolyte organic phase recovery;

[0047] (4) The water phase after separation of the electrolyte is added with a flocculant at 4% of the mass of the water phase, the flocculant is a polymeric ferric sulfate solution with a mass concentration of 30%, after stirring uniformly, standing for 10 min and filtering, a filter cake and a filtrate are obtained, the filter cake is mainly a mixture of battery powder, lithium fluoride, a small amount of ferric phosphate and polymeric ferric sulfate, which is used as a raw material for later leaching, and valuable metal elements are further recovered;

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

[0049] (6) The lithium-containing filtrate is heated to 35℃, 20% sodium carbonate solution is added to the solution until the pH is 8, and lithium carbonate precipitate is obtained by standing, and then the crude lithium carbonate is obtained by filtering and washing with pure water, and the filtrate after filtering is reused as water for underwater crushing of retired lithium batteries, so that the water is completely recycled, and there is no external discharge in the whole system, and the recovery rate of lithium ions can reach 100%.

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

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

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

[0053] Table 2. Filter cake element composition table

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

[0055] Example 2:

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

[0057] Example 3:

[0058] A method for recycling waste water of underwater crushing of retired lithium batteries, which is different from example 1 only in that the demulsifier in this example is prepared by uniformly mixing didecyldimethylammonium chloride and isopropanolamine, the mass ratio of didecyldimethylammonium chloride in the demulsifier is 20%, the mass ratio of isopropanolamine in the demulsifier is 80%, and the other conditions are the same as those in example 1.

[0059] Example 4:

[0060] A method for recycling waste water of underwater crushing of retired lithium batteries, which is different from example 1 only in that the demulsifier in this example is prepared by uniformly mixing didecyldimethylammonium chloride and isopropanolamine, the mass ratio of didecyldimethylammonium chloride in the demulsifier is 20%, the mass ratio of isopropanolamine in the demulsifier is 80%, and the other conditions are the same as those in example 1.

[0061] Example 5:

[0062] A method for recycling waste water of underwater crushing of retired lithium batteries, which is different from example 1 only in that the demulsifier in this example is prepared by uniformly mixing didecyldimethylammonium chloride and isopropanolamine, the mass ratio of didecyldimethylammonium chloride in the demulsifier is 20%, the mass ratio of isopropanolamine in the demulsifier is 80%, and the other conditions are the same as those in example 1.

[0063] Example 6:

[0064] A method for recycling waste water of underwater crushing of retired lithium batteries, which is different from example 1 only in that the demulsifier in this example is prepared by uniformly mixing didecyldimethylammonium chloride and isopropanolamine, the mass ratio of didecyldimethylammonium chloride in the demulsifier is 20%, the mass ratio of isopropanolamine in the demulsifier is 80%, and the other conditions are the same as those in example 1.

[0065] Comparative example 1:

[0066] A method for recycling wastewater from underwater crushing of retired lithium batteries, and the difference from Example 1 is only that no demulsifier is added in step (2) of Example 1 in the present comparative example, and the rest of the conditions are the same as in Example 1.

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

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

[0069] Table 4. Filter cake element composition table of Comparative Example 1

[0070] Li (%) F(％) P(％) C(％) Moisture content (%) Filter cake composition 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, and the difference from Example 1 is only that the demulsifier in the present comparative example is a single didecyldimethylammonium chloride, and the rest of the conditions are the same as in Example 1.

[0073] Comparative Example 3:

[0074] A method for recycling wastewater from underwater crushing of retired lithium batteries, and the difference from Example 1 is only that no flocculant is added for flocculation in step (4) in the present comparative example, and the rest of the conditions are the same as in Example 1. As a result, the filtration effect is poor in step (4), and the filter cloth is blocked.

[0075] Comparative Example 4:

[0076] A method for recycling wastewater from underwater crushing of retired lithium batteries, and the difference from Example 1 is only that ethanol is used instead of tetradecyl trimethyl ammonium chloride in the present comparative example, and the rest of the conditions are the same as in Example 1.

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

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

[0079] Table 6. Filter cake element composition table of Comparative Example 4

[0080] Li (%) F(％) P(％) C(％) Moisture content (%) Filter cake composition Li (mg / L) F (mg / L) P (mg / L) COD (mg / L) Wastewater quality Recycle water quality Li (%) Moisture content (%) Filter cake composition 0.8 1.9 3.8 19.1 26％

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

[0082] Table 7. Demulsification performance test

[0083]

[0084]

[0085] Table 8. Flocculation filtration performance test

[0086]

[0087] From the examples 1-6 in table 7, it can be seen that the demulsifier prepared by using two kinds of surfactants has better demulsification effect, and the oil-liquid two-phase can be separated after a short time of standing, the oil-water interface is clear, and the removed electrolyte contains about 10% of water. It can be seen from the comparative example 1 and the comparative example 1 that without adding the demulsifier, the electrolyte is difficult to separate, and there is no separation phenomenon after standing for 1 h. It can be seen from the comparative example 1 and the comparative example 4 that without adding the specific demulsifier of the application, the electrolyte is difficult to separate, and there is no separation phenomenon after standing for 1 h. It can be seen from the comparative example 1 and the comparative example 2 that the effect of adding only one kind of surfactant is poor. It can be seen from table 8 that the filtration effect is poor when no flocculating agent in the application is added during filtration, 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: Includes the following steps: (1) Add a demulsifier to the wastewater generated by underwater crushing of retired lithium batteries, mix and then separate the liquids by ultrasonication to obtain an electrolyte phase and an aqueous phase. The demulsifier is a mixture of demulsifier A and demulsifier B. Demulsifier A is at least one of dialcyldimethylammonium chloride and tetradecyltrimethylammonium chloride, and demulsifier B is at least one of triethylamine, ethanolamine and isopropanolamine. (2) Add flocculant to the aqueous phase obtained in step (1), mix and let stand to flocculate, filter to obtain filter cake and first filtrate; (3) Add lithium hydroxide solution to the first filtrate obtained in step (2) to adjust the pH to 2-5, precipitate excess iron ions, and then filter to obtain the second filtrate; (4) After heating the second filtrate obtained in step (3), add carbonate solution to adjust the pH to alkaline, let it stand, filter to obtain lithium carbonate precipitate and third filtrate, wash the lithium carbonate precipitate to obtain crude lithium carbonate, and reuse the third filtrate for underwater crushing process water of retired lithium batteries; in step (1), the mass ratio of demulsifier A in the demulsifier is 20%-40%, and the mass ratio of demulsifier B in the demulsifier is 60%-80%; in step (4), the heating is to raise the temperature of the second filtrate to 30-50℃.

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

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

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

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

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

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

8. A method for recycling wastewater from underwater crushing of decommissioned lithium batteries according to claim 1, characterized in that: The wastewater generated from the underwater crushing of retired lithium batteries in step (1) originates from the process of crushing retired lithium battery cells. The process includes the following steps: immersing retired lithium battery cells with voltage in water for crushing or shredding; soaking the crushed cells underwater and then using a sieve to remove the crushed battery material; drying the wet crushed battery material and then crushing and sorting it to obtain battery powder, copper material, aluminum material, and separator; the remainder is the wastewater generated from underwater crushing of retired lithium batteries.

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