A method for removing impurities from a waste battery leachate

Abstract

The application provides a method for removing impurities from waste battery leaching solution, which comprises the following steps: (1) acid leaching waste electrode active material to obtain leaching solution; (2) adding a first reducing agent to the leaching solution to remove copper ions; (3) adding a sodium salt and a second reducing agent to the leaching solution to remove aluminum ions and fluorine ions; the step (2) and the step (3) are carried out in no particular order or simultaneously. The method for removing impurities can achieve the purpose of deep impurity removal through simple chemical precipitation, does not need to use an extractant, does not have the residue of the extractant, has low or no loss of iron and lithium, and the impurity removal residue is easy to filter. Meanwhile, the method can obtain battery-grade iron phosphate with high added value, realizes short-process high-value recovery and regeneration of valuable elements, and has the advantages of low cost, high efficiency, and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery recycling and relates to a method for removing impurities from waste battery leaching solution. BACKGROUND

[0002] Lithium iron phosphate (LiFePO4) batteries have gradually become one of the mainstream choices for vehicle power lithium ion batteries due to their cost advantage and high safety, but due to the limited service life of lithium ion batteries, a large number of LiFePO4 batteries will inevitably be discarded over time. After pretreatment processes such as crushing and sorting, waste LiFePO4 batteries obtain lithium iron phosphate waste (LiFePO4 / C / Al / Cu / Fe, etc.), which contains rare and precious metal element lithium and abundant iron and phosphorus. If it is reasonably recycled and utilized, it can alleviate the consumption of mineral resources and produce good economic and social benefits.

[0003] CN 102208707A discloses a method for repairing and regenerating waste lithium iron phosphate battery positive electrode material. Lithium source solution or suspension is used for hydrothermal reaction or solvent thermal reaction with recovered waste lithium iron phosphate battery material to generate lithium iron phosphate, or the recovered waste lithium iron phosphate battery material is solid-phase ball milled and calcined with lithium source to directly supplement lithium in liquid phase or solid phase for the lithium-deficient waste lithium iron phosphate, and then coated with conductive agent or coated with conductive agent and doped with metal ions for targeted repair and regeneration. That is, the recovered lithium iron phosphate waste is mixed with lithium carbonate and ball milled or the lithium iron phosphate waste is placed in a lithium-containing solution for hydrothermal lithium supplementation, and the regenerated lithium iron phosphate is obtained by solid-phase repair. The solid-phase repair provides a good way for the recovery of lithium iron phosphate waste, but the purity of the lithium iron phosphate waste is high, which limits the application of the technology in industrialization.

[0004] CN 110459828A discloses a comprehensive recovery method for waste lithium iron phosphate battery positive electrode material. Waste lithium iron phosphate battery powder is leached with dilute acid and oxidizing agent to obtain a lithium-rich liquid, which is then purified and impurities are removed by precipitation to obtain lithium carbonate. FePO4 is obtained by acid leaching and purifying the leaching residue. This method realizes the recovery of waste lithium iron phosphate batteries. The above-mentioned selective lithium extraction technology has high universality and no special requirements for the purity of lithium iron phosphate waste, but the phosphorus-iron slag generated after lithium extraction is difficult to recycle and utilize, which makes the process not economically advantageous.

[0005] Therefore, the existing recycling methods for waste lithium iron phosphate batteries mainly involve stripping the positive electrode sheet to obtain the positive electrode material, followed by acid leaching to obtain a leachate. In order to precipitate battery-grade iron phosphate (with impurity content of Na≤0.01Wt.%, Cu≤0.005Wt.%, Al≤0.01Wt.%) and lithium carbonate, the leachate needs to be deeply cleaned of impurity ions. Current technologies mainly use extraction or hydroxide precipitation to remove aluminum and fluorine, but this results in the residue of the extractant and the loss of a large amount of iron and lithium.

[0006] Based on the above research, there is a need to provide a method for removing impurities from leachate of spent batteries, which can deeply remove Cu from the leachate. 2+ Al 3+ and F - Plasma extraction eliminates the residue of extractants and the loss of large amounts of iron and lithium, while also producing battery-grade iron phosphate. Summary of the Invention

[0007] The purpose of this invention is to provide a method for removing impurities from leachate of waste batteries, particularly a method for removing impurities from leachate of waste lithium iron phosphate batteries. This method achieves deep impurity removal through simple chemical precipitation, without the need for extractants, thus eliminating extractant residues. Furthermore, it results in low or no loss of iron and lithium, easy filtration of the impurity residue, and the production of high-value battery-grade iron phosphate, achieving short-process, high-value recovery and regeneration of valuable elements.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] This invention provides a method for removing impurities from leachate of waste batteries, the method comprising the following steps:

[0010] (1) The waste electrode active material is acid-leached to obtain leachate;

[0011] (2) Add a first reducing agent to the leachate obtained in step (1) to remove copper ions;

[0012] (3) Add sodium salt and a second reducing agent to the leachate obtained in step (1) to remove aluminum ions and fluoride ions;

[0013] Steps (2) and (3) can be performed in any order, or simultaneously.

[0014] This invention employs a coupled method of copper removal and internal fluorine removal to deeply remove Cu from the leachate of spent batteries. 2+ Al 3+ and F -Plasma is used to obtain a qualified precipitated iron phosphate pretreatment solution, which can then be used to produce high-value-added battery-grade iron phosphate, achieving short-process, high-value recovery and regeneration of valuable elements. Furthermore, the method described in this invention does not use extraction or hydroxide precipitation to remove aluminum and fluorine, thus eliminating extractant residues and significant losses of iron and lithium. The impurity residue is easily filtered, greatly reducing the requirements for production equipment and the overall production cost of the recycling process. Simultaneously, the impurity removal method described in this invention can simultaneously precipitate and remove copper, fluoride, and chloride ions, not only without affecting the impurity removal effect or causing loss of valuable elements, but also shortening the process flow and reducing costs.

[0015] When step (2) of the present invention is performed first, the copper-removed liquid is then subjected to the fluoride and aluminum ion removal steps of step (3); when step (3) is performed first, the fluoride and aluminum-removed liquid is then subjected to the copper removal steps of step (2).

[0016] Preferably, when steps (2) and (3) are performed simultaneously, a first reducing agent, a sodium salt, and a second reducing agent are added to the leachate in step (1) to simultaneously remove aluminum ions, fluoride ions, and copper ions, thereby obtaining a ferric phosphate precipitation pretreatment solution.

[0017] This invention removes fluoride and aluminum ions under a reducing atmosphere. Under reducing conditions, iron in the solution is ensured to exist as ferrous ions, and the loss of iron during the removal of aluminum and fluoride is significantly reduced. Copper ions are removed by reducing and precipitating them. Therefore, this invention can remove aluminum, fluoride, and copper ions simultaneously in one step, achieving not only a high removal rate but also the removal efficiency of stepwise processes. Compared to stepwise impurity removal, it shortens the impurity removal process, reduces the requirements for production equipment and production costs, and enables the impurity removal method of this invention to be applied on a large scale in industrial applications.

[0018] Preferably, when steps (2) and (3) are performed simultaneously, the molar ratio of sodium ions, aluminum ions and fluoride ions in the leachate is (1-5):1:6, for example, it can be 1:1:6, 3:1:6 or 5:1:6, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] In order to achieve deep removal of fluorine and aluminum, this invention controls the molar ratio of sodium ions, aluminum ions and fluoride ions. This not only enables deep removal of aluminum ions, but also enables the simultaneous precipitation and deep removal of fluoride and aluminum ions, thus achieving endogenous removal of fluorine and aluminum. If the molar ratio of sodium ions, aluminum ions and fluoride ions is not within the above range, it will affect the removal rate of impurity ions.

[0020] Preferably, when steps (2) and (3) are performed simultaneously, the pH of the leachate is 1-3, for example, it can be 1, 2 or 3, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] Preferably, when steps (2) and (3) are performed simultaneously, the reaction temperature is 50-80℃, for example, 50℃, 60℃, 70℃ or 80℃, and the reaction time is 30-180min, for example, 30min, 100min, 150min or 180min, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] Preferably, when steps (2) and (3) are performed simultaneously, the amount of the first reducing agent added is 1-10 g / L, for example, it can be 1 g / L, 5 g / L or 10 g / L, and the amount of the second reducing agent added is 0.1-1 g / L, for example, it can be 0.1 g / L, 0.5 g / L or 1 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0023] When removing copper ions, fluoride ions and chloride ions simultaneously, this invention requires both precipitation to remove copper ions and a specific reducing atmosphere to promote the precipitation of aluminum fluoride. Therefore, specific amounts of a first reducing agent and a second reducing agent need to be added to ensure the deep removal of impurity ions; otherwise, the removal rate of impurity ions will be reduced to some extent.

[0024] Preferably, when steps (2) and (3) are performed in any order, the pH of the leachate in step (2) is 1-5, for example, it can be 1, 2, 3, 4 or 5, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, when steps (2) and (3) are performed in any order, the reaction temperature of step (2) is 50-80℃, for example, 50℃, 60℃, 70℃ or 80℃, and the reaction time is 10-180min, for example, 10min, 50min, 100min, 150min or 180min, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, when steps (2) and (3) are performed in any order, the amount of the first reducing agent added in step (2) is 1-10 g / L, for example, it can be 1 g / L, 5 g / L or 10 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, when steps (2) and (3) are performed in any order, the molar ratio of sodium ions, aluminum ions and fluoride ions in the leachate in step (3) is (1-5):1:6, for example, it can be 1:1:6, 2:1:6, 3:1:6, 4:1:6 or 5:1:6, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, when steps (2) and (3) are performed in any order, the reaction temperature of step (3) is 30-80℃, for example, it can be 30℃, 40℃, 50℃, 60℃, 70℃ or 80℃, and the reaction time is 30-240min, for example, it can be 30min, 100min, 150min, 200min or 240min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0029] Preferably, when steps (2) and (3) are performed in any order, the pH of the leachate in step (3) is 1-3, for example, it can be 1, 2 or 3, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, when steps (2) and (3) are performed in any order, the amount of the second reducing agent added in step (3) is 0.1-1 g / L, for example, it can be 0.1 g / L, 0.5 g / L or 1 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] Preferably, the first reducing agent comprises iron powder.

[0032] Preferably, the second reducing agent comprises a water-soluble reducing agent and / or iron powder, and more preferably a water-soluble reducing agent.

[0033] The second reducing agent of the present invention is preferably a water-soluble reducing substance. Compared with reducing agents such as iron powder that are insoluble in water, the water-soluble reducing agent can enable the second reducing agent to play a different role than the first reducing agent, promote the simultaneous precipitation of fluoride ions and aluminum ions, and further improve the impurity removal efficiency.

[0034] Preferably, the water-soluble reducing agent includes any one or a combination of at least two of Na2SO3, citric acid, ascorbic acid, or hydrazine sulfate.

[0035] Preferably, the sodium salt comprises sodium fluoride and / or sodium carbonate.

[0036] Preferably, the leaching solid-liquid ratio in step (1) is 100-500 g / L, for example, it can be 100 g / L, 250 g / L or 500 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the acid leaching temperature in step (1) is 50-90℃, for example, 50℃, 60℃, 70℃, 80℃ or 90℃, and the time is 60-240min, for example, 60min, 100min, 150min, 200min or 240min, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0038] Preferably, the inorganic acid used in step (1) for acid leaching includes any one or a combination of at least two of HCl, H2SO4, HNO3 or H3PO4.

[0039] Preferably, the concentration of the inorganic acid is 1-5 mol / L, for example, it can be 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L or 5 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] Preferably, the waste electrode active material in step (1) includes positive electrode active material, and the content of the positive electrode active material is not less than 10 wt%, for example, it can be 10 wt%, 30 wt%, 50 wt%, 70 wt% or 90 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable. Preferably, it is 45-95 wt%, and more preferably, it is 45-85 wt%.

[0041] Preferably, the waste electrode active material in step (1) further includes a conductive agent.

[0042] Preferably, the active material of the waste battery in step (1) further includes a negative electrode active material, a binder, a positive electrode current collector, and a negative electrode current collector.

[0043] The active materials of the waste batteries described in this invention can include not only positive electrode active materials, but also positive electrode active materials, negative electrode active materials, binders, conductive agents, positive electrode current collectors, and negative electrode current collectors. The presence of other substances will not affect the impurity removal effect. Therefore, this invention does not require fine sorting of non-positive electrode active materials. Even when including other substances such as negative electrodes, it still has excellent impurity removal effect, improving the convenience of the overall recycling process.

[0044] Preferably, the waste electrode active material in step (1) is obtained by discharging, dismantling, crushing, roasting and sieving waste batteries.

[0045] Preferably, the impurity removal method removes copper ions, aluminum ions and fluoride ions to obtain iron phosphate precipitation pretreatment solution, and the iron phosphate slag pretreatment solution is post-treated to recover lithium compounds and battery-grade iron phosphate.

[0046] As a preferred embodiment of the present invention, the impurity removal method includes the following steps:

[0047] (1) The waste electrode active material is acid-leached at 50-90℃ with a leaching solid-liquid ratio of 100-500g / L for 60-240min, wherein the concentration of inorganic acid used in acid leaching is 1-5mol / L, to obtain leachate.

[0048] The active materials of the waste batteries include positive electrode active materials, conductive agents, negative electrode active materials, binders, positive electrode current collectors, and negative electrode current collectors;

[0049] (2) Add the first reducing agent, sodium salt and second reducing agent to the leachate in step (1), and react at 50-80℃ for 30-180 min to remove aluminum ions, fluoride ions and copper ions simultaneously to obtain iron phosphate precipitation pretreatment solution.

[0050] The molar ratio of sodium ions, aluminum ions and fluoride ions in the leachate is (1-5):1:6, and the pH of the leachate is 1-3; the amount of the first reducing agent added is 1-10 g / L, and the amount of the second reducing agent added is 0.1-1 g / L.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] (1) The present invention adopts a copper removal and internal fluorine removal aluminum coupling method, which can successfully control the content of impurity ions such as Cu and Al in the regenerated iron phosphate sample to meet the requirements of battery-grade iron phosphate.

[0053] (2) The impurity removal method described in this invention has strong applicability to raw materials, simple process, good process repeatability, and can be scaled up for industrial production.

[0054] (3) Compared with the existing copper and aluminum removal technology for recycling waste lithium iron phosphate batteries, the present invention does not require the use of an extractant in the process, and the loss of iron and lithium is low or non-existent. The impurities are easy to filter, and deep removal can be achieved through simple chemical precipitation. This can greatly reduce the requirements for production equipment and the production cost of the entire recycling process.

[0055] (4) The method described in this invention is suitable for forming a closed-loop process, which will not generate secondary pollution, while taking into account both environmental protection and economic benefits. The process is simple, the production cost is low, and it is suitable for large-scale industrial production.

[0056] (5) The method described in this invention can obtain a precipitated iron phosphate pretreatment solution that meets the requirements, which can be used to subsequently produce high-value-added battery-grade iron phosphate, realizing a short-process, high-value recovery and regeneration of valuable elements. Attached Figure Description

[0057] Figure 1 This is a flowchart of the impurity removal method described in Embodiment 1 of the present invention;

[0058] Figure 2 This is a flowchart of the impurity removal method described in Embodiment 4 of the present invention;

[0059] Figure 3 The image shows the XRD pattern of the defluorinated aluminum slag described in Example 4 of this invention. Detailed Implementation

[0060] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0061] Example 1

[0062] This embodiment provides a method for removing impurities from leachate of spent batteries. The flowchart of the impurity removal method is as follows: Figure 1 As shown, it includes the following steps:

[0063] (1) The waste LiFePO4 battery was soaked in a 5% NaCl salt solution and discharged until the termination voltage was 1V. The battery cell was disassembled and then mechanically crushed as a whole. The fragments with a particle size of less than 0.1mm were screened out. The fragments were roasted at 450℃ to obtain waste electrode active materials. The fluorine-containing waste gas from roasting was absorbed by lime water to obtain calcium fluoride.

[0064] Waste electrode active materials were leached at 60°C with a leaching solid-liquid ratio of 100 g / L using 2 mol / L H2SO4 for 180 min, and then the leachate was obtained by filtration.

[0065] The active materials of the waste batteries include positive electrode active materials, conductive agents, negative electrode active materials, binders, positive electrode current collectors, and negative electrode current collectors;

[0066] (2) Add a first reducing agent, sodium fluoride and a second reducing agent to the leachate obtained in step (1), and react at 60°C for 60 min to remove aluminum ions, fluoride ions and copper ions simultaneously to obtain iron phosphate precipitation pretreatment solution; the iron phosphate precipitation pretreatment solution is used to precipitate iron phosphate and precipitate lithium to obtain battery-grade iron phosphate.

[0067] The molar ratio of sodium ions, aluminum ions, and fluoride ions in the leachate is 5:1:6, and the pH of the leachate is 2; the amount of the first reducing agent added is 5 g / L, and the amount of the second reducing agent added is 0.5 g / L.

[0068] The first reducing agent is iron powder, and the second reducing agent is Na2SO3.

[0069] Example 2

[0070] This embodiment provides a method for removing impurities from leachate of waste batteries, the method comprising the following steps:

[0071] (1) The waste LiFePO4 battery was soaked in a 5% NaCl salt solution and discharged until the termination voltage was 1V. The battery cell was disassembled and then mechanically crushed as a whole. The fragments with a particle size of less than 0.1mm were screened out. The fragments were roasted at 450℃ to obtain waste electrode active materials. The fluorine-containing waste gas from roasting was absorbed by lime water to obtain calcium fluoride.

[0072] Waste electrode active materials were leached at 90°C with a solid-liquid ratio of 250 g / L in 1 mol / L H2SO4 for 240 min, and then the leachate was obtained by filtration.

[0073] The active materials of the waste batteries include positive electrode active materials, conductive agents, negative electrode active materials, binders, positive electrode current collectors, and negative electrode current collectors;

[0074] (2) Add a first reducing agent, sodium fluoride and a second reducing agent to the leachate obtained in step (1), and react at 80°C for 30 min to remove aluminum ions, fluoride ions and copper ions simultaneously to obtain iron phosphate precipitation pretreatment solution; the iron phosphate precipitation pretreatment solution is used to precipitate iron phosphate and precipitate lithium to obtain battery-grade iron phosphate.

[0075] The molar ratio of sodium ions, aluminum ions, and fluoride ions in the leachate is 3:1:6, and the pH of the leachate is 1; the amount of the first reducing agent added is 10 g / L, and the amount of the second reducing agent added is 0.1 g / L.

[0076] The first reducing agent is iron powder, and the second reducing agent is citric acid.

[0077] Example 3

[0078] This embodiment provides a method for removing impurities from leachate of waste batteries, the method comprising the following steps:

[0079] (1) The waste LiFePO4 battery was soaked in a 5% NaCl salt solution and discharged until the termination voltage was 1V. The battery cell was disassembled and then mechanically crushed as a whole. The fragments with a particle size of less than 0.1mm were screened out. The fragments were roasted at 450℃ to obtain waste electrode active materials. The fluorine-containing waste gas from roasting was absorbed by lime water to obtain calcium fluoride.

[0080] Waste electrode active materials were leached at 50°C with a solid-liquid ratio of 500 g / L using 5 mol / L HCl for 60 min, and then the leachate was obtained by filtration.

[0081] The active materials of the waste batteries include positive electrode active materials, conductive agents, negative electrode active materials, binders, positive electrode current collectors, and negative electrode current collectors;

[0082] (2) Add a first reducing agent, sodium fluoride and a second reducing agent to the leachate obtained in step (1), and react at 50°C for 180 min to remove aluminum ions, fluoride ions and copper ions simultaneously to obtain iron phosphate precipitation pretreatment solution; the iron phosphate precipitation pretreatment solution is used to precipitate iron phosphate and precipitate lithium to obtain battery-grade iron phosphate.

[0083] The molar ratio of sodium ions, aluminum ions and fluoride ions in the leachate is 1:1:6, and the pH of the leachate is 3; the amount of the first reducing agent added is 1 g / L, and the amount of the second reducing agent added is 1 g / L.

[0084] The first reducing agent is iron powder, and the second reducing agent is Na2SO3.

[0085] Example 4

[0086] This embodiment provides a method for removing impurities from leachate of spent batteries. The flowchart of the impurity removal method is as follows: Figure 2 As shown, it includes the following steps:

[0087] (1) The waste LiFePO4 battery was soaked in a 5% NaCl salt solution and discharged until the termination voltage was 1V. The battery cell was disassembled and then mechanically crushed as a whole. The fragments with a particle size of less than 0.1mm were screened out. The fragments were roasted at 450℃ to obtain waste electrode active materials. The fluorine-containing waste gas from roasting was absorbed by lime water to obtain calcium fluoride.

[0088] Waste electrode active materials were leached at 60°C with a leaching solid-liquid ratio of 100 g / L using 2 mol / L H2SO4 for 180 min, and then the leachate was obtained by filtration.

[0089] The active materials of the waste batteries include positive electrode active materials, conductive agents, negative electrode active materials, binders, positive electrode current collectors, and negative electrode current collectors;

[0090] (2) Add iron powder to the leachate obtained in step (1) and react at 60°C for 60 min to remove copper ions and obtain copper removal solution and copper removal slag.

[0091] The pH of the leachate is 2, and the amount of the first reducing agent added is 5 g / L.

[0092] (3) Add sodium fluoride and Na2SO3 to the copper removal solution obtained in step (2), and react at 60°C for 60 min to simultaneously remove aluminum ions, fluoride ions, and copper ions, obtaining ferric phosphate precipitation pretreatment solution and fluorinated aluminum slag. The XRD pattern of the fluorinated aluminum slag is shown in the figure. Figure 3 As shown, where, Figure 3 The lower part of the image shows the standard Na3AlF6 spectrum, and the upper part shows the XRD test results of the aluminum fluoride slag. The iron phosphate precipitation pretreatment solution is used to precipitate iron phosphate and lithium to obtain battery-grade iron phosphate.

[0093] The molar ratio of sodium ions, aluminum ions, and fluoride ions in the leachate is 5:1:6, the pH of the leachate is 2, and the amount of the second reducing agent added is 0.5 g / L.

[0094] Example 5

[0095] This embodiment provides a method for removing impurities from waste battery leachate. Except for the removal of aluminum fluoride in step (3) and the removal of copper in step (2) of the resulting aluminum fluoride-free liquid, the method is the same as that in embodiment 4.

[0096] Example 6

[0097] This embodiment provides a method for removing impurities from the leachate of waste batteries. Except for step (1), in which the active material of the waste battery only includes the positive electrode active material, the method is the same as in embodiment 1.

[0098] Example 7

[0099] This embodiment provides a method for removing impurities from leachate of waste batteries. Except for step (2), in which the amount of the second reducing agent added is 0.01 g / L, the method is the same as in embodiment 1.

[0100] Example 8

[0101] This embodiment provides a method for removing impurities from leachate of waste batteries. Except for step (2), in which the amount of the second reducing agent added is 2 g / L, the method is the same as in embodiment 1.

[0102] Example 9

[0103] This embodiment provides a method for removing impurities from leachate of waste batteries. Except for step (2), in which the second reducing agent is iron powder, the method is the same as in embodiment 1.

[0104] Example 10

[0105] This embodiment provides a method for removing impurities from leachate of waste batteries. Except for the molar ratio of sodium ions, aluminum ions and fluoride ions in the leachate in step (2) being 0.5:1:6, the method is the same as in embodiment 1.

[0106] Example 11

[0107] This embodiment provides a method for removing impurities from leachate of waste batteries. Except for the molar ratio of sodium ions, aluminum ions and fluoride ions in the leachate in step (2) being 8:1:6, the method is the same as in embodiment 1.

[0108] Comparative Example 1

[0109] This comparative example provides a method for removing impurities from the leachate of waste batteries. Except for step (2), in which the first reducing agent is not added, the method is the same as in Example 1.

[0110] Comparative Example 2

[0111] This comparative example provides a method for removing impurities from the leachate of waste batteries. Except for step (2), in which a second reducing agent is not added, the method is the same as in Example 1.

[0112] The above examples and comparative examples were used to test the removal rate of impurity ions and the loss rate of major elements. The tests were conducted using an atomic absorption spectrometer. The results showed that the leaching rates of major elements Li, Fe, and P all exceeded 99%. Other test results are shown in the table below.

[0113] Table 1

[0114]

[0115]

[0116] As can be seen from Table 1:

[0117] The impurity removal method provided by this invention can deeply remove aluminum ions, fluoride ions, and copper ions, resulting in a low impurity ion content in the final byproduct, ferric phosphate. A comparison of Example 1 and Comparative Examples 1-2 shows that in the simultaneous removal of aluminum, fluoride, and copper ions, both the first and second reducing agents need to be added to ensure deep removal of copper ions, as well as aluminum and fluoride ions. Examples 1 and 4-5 show that the simultaneous copper removal and aluminum / fluoride removal steps of this invention achieve comparable impurity removal results to steps performed separately. This invention enables deep impurity removal from the leachate in a shorter process. As shown in Examples 1 and 6, the presence of negative electrode active material, conductive agent, binder, positive electrode current collector, and negative electrode current collector in the raw material to be recycled does not affect the impurity removal effect, and the impurity removal method described in this invention is more convenient. As shown in Examples 1 and 7-9, the amount and type of the second reducing agent added will affect the impurity removal effect of aluminum and fluorine. As shown in Examples 1 and 10-11, the molar ratio of ions, aluminum ions, and fluoride ions in the leachate affects the impurity removal effect of aluminum and fluorine.

[0118] In summary, this invention provides a method for removing impurities from leachate of waste batteries. This method achieves deep impurity removal through simple chemical precipitation, without the need for extractants, thus eliminating extractant residues. Furthermore, it results in low or no loss of iron and lithium, and the removed residue is easy to filter. Simultaneously, it yields high-value-added battery-grade iron phosphate, realizing a short-process, high-value recovery and regeneration of valuable elements.

[0119] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for removing impurities from leachate of waste batteries, characterized in that, The impurity removal method includes the following steps: (1) The waste electrode active material is acid-leached to obtain leachate; (2) Add a first reducing agent to the leachate from step (1) to remove copper ions; (3) Add sodium salt and a second reducing agent to the leachate from step (1) to remove aluminum ions and fluoride ions; Steps (2) and (3) can be performed in any order, or simultaneously. The molar ratio of sodium ions, aluminum ions and fluoride ions in the leachate in step (3) is (1-5):1:6; The second reducing agent includes a water-soluble reducing agent; The water-soluble reducing agent includes any one or a combination of at least two of Na2SO3, citric acid, ascorbic acid, or hydrazine sulfate; The sodium salt includes sodium carbonate; Step (2) The amount of the first reducing agent added is 1-10 g / L; In step (3), the amount of the second reducing agent added is 0.1-1 g / L.

2. The impurity removal method according to claim 1, characterized in that, When steps (2) and (3) are performed simultaneously, a first reducing agent, a sodium salt, and a second reducing agent are added to the leachate in step (1) to simultaneously remove aluminum ions, fluoride ions, and copper ions, thereby obtaining a ferric phosphate precipitation pretreatment solution.

3. The impurity removal method according to claim 1, characterized in that, When steps (2) and (3) are performed simultaneously, the pH of the leachate is 1-3.

4. The impurity removal method according to claim 1, characterized in that, When steps (2) and (3) are performed simultaneously, the reaction temperature is 50-80℃ and the reaction time is 30-180min.

5. The impurity removal method according to claim 1, characterized in that, When steps (2) and (3) are performed separately without any order, the pH of the leachate in step (2) is 1-5.

6. The impurity removal method according to claim 1, characterized in that, When steps (2) and (3) are performed in any order, the reaction temperature of step (2) is 50-80℃ and the reaction time is 10-180min.

7. The impurity removal method according to claim 1, characterized in that, When steps (2) and (3) are performed in any order, the reaction temperature of step (3) is 30-80℃ and the reaction time is 30-240min.

8. The impurity removal method according to claim 1, characterized in that, When steps (2) and (3) are performed separately without any order, the pH of the leachate in step (3) is 1-3.

9. The impurity removal method according to claim 1, characterized in that, The first reducing agent includes iron powder.

10. The impurity removal method according to claim 1, characterized in that, The sodium salts include sodium fluoride and sodium carbonate.

11. The impurity removal method according to claim 1, characterized in that, The solid-liquid ratio of the acid leaching in step (1) is 100-500 g / L.

12. The impurity removal method according to claim 1, characterized in that, The acid leaching temperature in step (1) is 50-90℃ and the time is 60-240min.

13. The impurity removal method according to claim 1, characterized in that, The inorganic acid used in step (1) for acid leaching includes any one or a combination of at least two of HCl, H2SO4, HNO3 or H3PO4.

14. The impurity removal method according to claim 13, characterized in that, The concentration of the inorganic acid is 1-5 mol / L.

15. The impurity removal method according to claim 1, characterized in that, The waste electrode active material mentioned in step (1) includes positive electrode active material.

16. The impurity removal method according to claim 1, characterized in that, The waste electrode active material mentioned in step (1) also includes a conductive agent.

17. The impurity removal method according to claim 1, characterized in that, The waste electrode active material in step (1) also includes negative electrode active material, binder, positive electrode current collector and negative electrode current collector.

18. The impurity removal method according to claim 1, characterized in that, The waste electrode active material in step (1) is obtained by discharging, dismantling, crushing, roasting and sieving waste batteries.

19. The impurity removal method according to claim 1, characterized in that, The impurity removal method removes copper ions, aluminum ions, and fluoride ions to obtain iron phosphate precipitation pretreatment solution. The iron phosphate precipitation pretreatment solution is then post-treated to recover lithium compounds and battery-grade iron phosphate.

20. The impurity removal method according to claim 1, characterized in that, The impurity removal method includes the following steps: (1) The waste electrode active material is acid-leached at 50-90℃ with a leaching solid-liquid ratio of 100-500g / L for 60-240min, wherein the concentration of inorganic acid used in acid leaching is 1-5mol / L, to obtain the leachate. The waste electrode active materials include positive electrode active materials, conductive agents, negative electrode active materials, binders, positive electrode current collectors, and negative electrode current collectors; (2) Add the first reducing agent, sodium salt and second reducing agent to the leachate in step (1), and react at 50-80℃ for 30-180 min to remove aluminum ions, fluoride ions and copper ions simultaneously to obtain iron phosphate precipitation pretreatment solution. The molar ratio of sodium ions, aluminum ions and fluoride ions in the leachate is (1-5):1:6, and the pH of the leachate is 1-3; the amount of the first reducing agent added is 1-10 g / L, and the amount of the second reducing agent added is 0.1-1 g / L.

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