Method for recycling lithium from waste lithium iron phosphate battery black powder

Abstract

The invention provides a method for recovering lithium from waste lithium iron phosphate battery black powder, which comprises the following steps: (1) mixing the waste lithium iron phosphate battery black powder with a leaching agent solution, and leaching to obtain a leaching solution; (2) mixing the leachate with a synergistic extraction agent, and performing extraction treatment to obtain raffinate and extract liquor containing Li < + > and leaching agent cations; (3) performing step-by-step reverse extraction on the extraction liquid containing Li < + > and leaching agent cations to obtain a lithium product and a solution containing the leaching agent cations; wherein a leaching agent in the leaching agent solution comprises FeCl3 (FeCl3). According to the method provided by the invention, no strong acid or strong alkali is added in the whole process, the solution containing the leaching agent cations and the raffinate can be recycled, and no wastewater is discharged; moreover, the process is environment-friendly, lithium can be directly extracted without impurity removal, the lithium yield is high, the concentration of lithium obtained through reverse extraction is high, a lithium product can be obtained through direct precipitation, the energy consumption is low, and the cost is low.

Description

Technical Field

[0001] The present invention belongs to the field of recycling, treatment and resource utilization of electronic waste, and particularly relates to a method for recovering lithium from black powder of waste lithium iron phosphate batteries. Background Art

[0002] In recent years, under the background of the era of green environmental protection, new energy vehicles in China have shown rapid growth. Lithium iron phosphate power batteries are widely used in fields such as electric vehicles and energy storage power stations due to their excellent safety, stability and cycle performance, as well as their low price and pollution-free characteristics. With the continuous increase in production capacity, the number of waste lithium iron phosphate batteries is increasing day by day, and the resulting resource shortage and environmental problems are becoming increasingly severe. Therefore, developing a clean and efficient method for treating black powder of waste lithium iron phosphate batteries has important practical significance.

[0003] Currently, the traditional process for treating black powder of waste lithium iron phosphate batteries is to use strong acids (sulfuric acid or hydrochloric acid) in combination with hydrogen peroxide for selective leaching, obtain a lithium-containing leaching solution, deeply remove impurities, then perform evaporation and concentration. After concentrating the lithium concentration to more than 15 g / L, lithium carbonate products are obtained by precipitation. However, it has problems such as large consumption of strong acids and hydrogen peroxide and high treatment costs; moreover, the lithium concentration in the leaching solution cannot be directly precipitated, and a large amount of water needs to be evaporated during the evaporation process, resulting in high energy consumption.

[0004] Therefore, it is urgent to design a method to efficiently recover lithium elements from black powder of waste lithium iron phosphate batteries in a low-cost and environmentally friendly manner. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the purpose of the present invention is to provide a method for recovering lithium from black powder of waste lithium iron phosphate batteries. The method provided by the present invention does not add strong acids or strong alkalis throughout the process, and the solution containing the leaching agent cation and the raffinate can be recycled without wastewater discharge; moreover, the process is environmentally friendly, can directly extract lithium without impurity removal, has a high lithium recovery rate, and the lithium concentration obtained by back-extraction is high, and lithium products can be directly precipitated, with low energy consumption and low cost.

[0006] To achieve the purpose of the present invention, the following technical solutions are adopted:

[0007] In the first aspect, the present invention provides a method for recovering lithium from black powder of waste lithium iron phosphate batteries, and the method includes the following steps:

[0008] (1) Mix black powder of waste lithium iron phosphate batteries with a leaching agent solution and perform leaching treatment to obtain a leaching solution;

[0009] (2) Mix the leaching solution with a synergistic extractant and perform extraction treatment to obtain a raffinate and an extraction solution containing Li + and cations of the leaching agent;

[0010] (3) Perform stepwise back-extraction on the extract containing Li + and the cations of the leaching agent to obtain a lithium product and a solution containing the cations of the leaching agent;

[0011] Among them, the leaching agent in the leaching agent solution includes FeCl3.

[0012] The method provided by the present invention does not require the addition of strong acids or strong bases throughout the process, and the solution containing the cations of the leaching agent and the raffinate can be recycled without wastewater discharge; moreover, this process is environmentally friendly, can directly extract lithium without impurity removal, has a high lithium recovery rate, and the lithium concentration obtained by back-extraction is high, and the lithium product can be directly precipitated, with low energy consumption and low cost.

[0013] As a preferred technical solution of the present invention, the molar ratio of LiFePO4 in the waste lithium iron phosphate battery black powder in step (1) to the leaching agent in the leaching agent solution is 1:(0.5 - 1.5), for example, it can be 1:0.5, 1:0.75, 1:1, 1:1.25 or 1:1.5, etc.

[0014] Preferably, the leaching agent in the leaching agent solution in step (1) further includes any one or a combination of at least two of NaCl, KCl, HCl, MgCl2, CaCl2 or AlCl3.

[0015] As a preferred technical solution of the present invention, during the leaching treatment in step (1), the chloride ion concentration of the mixed solution > 5 mol / L, for example, it can be 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L or 8 mol / L, etc.

[0016] In the present invention, adjusting the chloride ion concentration of the mixed solution > 5 mol / L during the leaching treatment in step (1) helps to improve the leaching effect of lithium and meet the chloride ion concentration requirements of the co-extraction system for the lithium extraction process.

[0017] It should be noted that the present invention does not limit the adjustment method of the chloride ion concentration of the mixed solution > 5 mol / L. Exemplarily, for example, it can be by supplementing chlorides.

[0018] Preferably, the temperature of the leaching treatment in step (1) is 30 - 80 °C, for example, it can be 30 °C, 40 °C, 50 °C, 60 °C, 70 °C or 80 °C, etc., and the time is 0.5 - 3 h, for example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h or 3 h, etc.

[0019] As a preferred technical solution of the present invention, the co-extraction agent in step (2) includes a neutral phosphine extractant and an acidic phosphine extractant.

[0020] In the present invention, the combination of a neutral phosphine extractant and an acidic phosphine extractant is synergistically combined, which can improve the extraction effect of lithium, and on this premise, high-efficiency stripping of lithium can be achieved with low acidity or an aqueous solution, reducing the consumption of a precipitant (such as sodium carbonate) during the lithium precipitation process and lowering the cost.

[0021] Preferably, the volume ratio of the neutral phosphine extractant to the acidic phosphine extractant is (2 - 0.25):1, and for example, it can be 0.25:1, 0.5:1, 0.75:1, 1:1, 1.5:1, 2:1, etc.

[0022] In the present invention, if the volume ratio of the neutral phosphine extractant to the acidic phosphine extractant is too small, the impurity extraction rate is high and the purity of the lithium product is low; if the volume ratio of the neutral phosphine extractant to the acidic phosphine extractant is too large, the lithium extraction rate is low and the overall lithium yield is low.

[0023] Preferably, the neutral phosphine extractant includes any one or a combination of at least two of tributyl phosphate, tri-sec-butyl phosphate, triamyl phosphate, triisopentyl phosphate, or dimethylheptyl methylphosphonate.

[0024] Preferably, the acidic phosphine extractant includes any one or a combination of at least two of bis(2-ethylhexyl) phosphate, 2-ethylhexyl 2-ethylhexyl phosphate, bis(2,2,4-trimethylpentyl) phosphinic acid, or 2-ethylhexyl phosphinic acid.

[0025] Preferably, a diluent is further added during the mixing process in step (2).

[0026] In the present invention, the role of the diluent is to reduce the viscosity of the mixed solution during the extraction treatment in step (2) and improve the fluidity.

[0027] Preferably, the volume ratio of the synergistic extractant to the diluent in step (2) is (1 - 0.5):(1 - 3). Among them, the selection range of the synergistic extractant "1 - 0.5" can be, for example, 0.5, 0.6, 0.7, 0.8, 0.9, or 1, etc., and the selection range of the diluent "1 - 3" can be, for example, 1, 1.5, 2, 2.5, or 3, etc.

[0028] In the present invention, if the volume ratio of the synergistic extractant to the diluent is too small, that is, the amount of the diluent is too large, the extraction effect of lithium is poor; if the volume ratio of the synergistic extractant to the diluent is too large, that is, the amount of the diluent is too small, the viscosity of the extraction system is large and the fluidity is poor, which is not conducive to industrial production.

[0029] Preferably, the diluent includes hydrocarbon compounds and / or alcohol compounds.

[0030] Preferably, the number of carbon atoms in the hydrocarbon is 7 - 17, for example, it can be 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, or 17, etc. Exemplarily, for example, it can be 260# solvent naphtha (a hydrocarbon mixture of C11 - C17), aromatic hydrocarbon S150 (C9H 12 ), or n - heptane C7H 16 etc.

[0031] As a preferred technical solution of the present invention, the volume ratio of the leaching solution to the synergistic extractant in step (2) is 1:(0.25 - 5), for example, it can be 1:0.25, 1:0.5, 1:1, 1:2, 1:3, 1:4, or 1:5, etc.

[0032] In the present invention, if the volume ratio of the leaching solution to the synergistic extractant is too small, the extraction rate of impurity ions is high and the product purity is low; if the volume ratio of the leaching solution to the synergistic extractant is too large, the extraction effect of lithium is poor, the residual lithium concentration in the raffinate is high, and the lithium recovery rate is low.

[0033] Preferably, the extraction treatment method in step (2) includes a multi - stage counter - current method, and the number of stages of the multi - stage counter - current method is 2 - 8 stages, for example, it can be 2 stages, 4 stages, 6 stages, or 8 stages, etc.

[0034] As a preferred technical solution of the present invention, the specific steps of the step - by - step stripping include:

[0035] (a) Mix the extraction solution containing Li + , the cation of the leaching agent and the stripping agent, and conduct the stripping treatment of Li + to obtain a lithium - rich solution and a stripping raffinate;

[0036] (b) Mix the lithium - rich solution and the precipitating agent, and conduct a precipitation reaction to obtain a lithium product and a mother liquor for lithium precipitation;

[0037] (c) Adjust the pH value of the mother liquor for lithium precipitation to <2, then mix it with the stripping raffinate, and conduct the stripping treatment of the cation of the leaching agent to obtain a solution containing the cation of the leaching agent;

[0038] (d) Mix the solution containing the cation of the leaching agent and the raffinate, adjust the composition, and then return it to step (1) as the leaching agent solution for cyclic leaching.

[0039] By adopting the above - mentioned method for step - by - step stripping in the present invention, a high - purity lithium solution and a solution containing the cation of the leaching agent can be obtained respectively, and the solution containing the cation of the leaching agent can be recycled.

[0040] It should be noted that the "stripping raffinate" refers to the organic phase containing the cation of the leaching agent.

[0041] As a preferred technical solution of the present invention, the stripping agent in step (a) includes any one or a combination of at least two of HCl, NaCl, KCl, or LiCl.

[0042] Preferably, the volume ratio of the extraction solution to the stripping agent in step (a) is 1:(0.05 - 1), for example, it can be 1:0.05, 1:0.1, 1:0.3, 1:0.5, 1:0.7, or 1:0.9, etc.

[0043] In the present invention, if the volume ratio of the extraction solution to the stripping agent is too small, the lithium concentration in the stripping solution is low, and the subsequent treatment cost is high; if the volume ratio of the extraction solution to the stripping agent is too large, the lithium stripping is insufficient.

[0044] Preferably, the stripping treatment method in step (a) includes a multi-stage countercurrent method, and the number of stages of the multi-stage countercurrent method is 2 - 8 stages, for example, it can be 2 stages, 4 stages, 6 stages, or 8 stages, etc.

[0045] As a preferred technical solution of the present invention, the precipitating agent in step (b) includes sodium carbonate.

[0046] Preferably, the molar ratio of lithium to the precipitating agent in the lithium-rich solution in step (b) is 1:(0.5 - 1.5), for example, it can be 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, 1:1, or 1:1.5, etc.

[0047] Preferably, the temperature of the precipitation reaction in step (b) is 50 - 90°C, for example, it can be 50°C, 60°C, 70°C, 80°C, or 90°C, etc., and the time is 0.5 - 3 h, for example, it can be 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, or 3 h, etc.

[0048] As a preferred technical solution of the present invention, the pH regulator for adjusting the pH value of the mother liquor for lithium precipitation in step (c) is an acid, and the acid includes sulfuric acid and / or hydrochloric acid.

[0049] In the present invention, the purpose of adjusting the pH value of the mother liquor for lithium precipitation to <2 with an acid is to prevent the precipitation of leaching agent cations.

[0050] Preferably, the method of adjusting the composition in step (d) includes adjusting the chloride ion concentration of the mixed solution >5 mol / L (for example, it can be 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, or 8 mol / L, etc.) and adjusting the redox potential of the mixed solution >300 mV (for example, it can be 350 mV, 400 mV, 450 mV, or 500 mV, etc.).

[0051] It should be noted that the present invention does not limit the method for adjusting the chloride ion concentration of the mixed solution in step (d). Exemplarily, for example, it can be evaporation concentration and / or addition of chlorides, etc.

[0052] Preferably, the method for adjusting the redox potential of the mixed solution includes adding an oxidizing agent.

[0053] It should be noted that the present invention does not limit the type of the oxidizing agent. Exemplarily, for example, it can be potassium permanganate, hydrogen peroxide, perchloric acid, hypochlorous acid, etc.

[0054] As a preferred technical solution of the present invention, the method includes the following steps:

[0055] (Ⅰ) Mix the waste lithium iron phosphate battery black powder and the leaching agent solution containing FeCl3, and at the same time control the chloride ion concentration of the mixed solution > 5 mol / L, and then carry out leaching treatment at 30 - 80 °C for 0.5 - 3 h to obtain a leaching solution;

[0056] Among them, the molar ratio of LiFePO4 to FeCl3 in the waste lithium iron phosphate battery black powder is 1:(0.5 - 1.5);

[0057] (Ⅱ) Mix the leaching solution, the synergistic extractant and the diluent, and carry out extraction treatment to obtain a raffinate and an extraction solution containing Li + , Fe 3+ ;

[0058] Among them, the volume ratio of the leaching solution to the synergistic extractant is 1:(0.25 - 5), the synergistic extractant includes a neutral phosphine extractant and an acidic phosphine extractant with a volume ratio of (2 - 0.25):1, and the volume ratio of the synergistic extractant to the diluent is (1 - 0.5):(1 - 3);

[0059] (Ⅲ) Mix the extraction solution containing Li + , Fe 3+ and the stripping agent, and carry out Li + stripping treatment to obtain a lithium-rich solution and a stripping raffinate;

[0060] Among them, the volume ratio of the extraction solution to the stripping agent is 1:(0.05 - 1);

[0061] (Ⅳ) Mix the lithium-rich solution and sodium carbonate, and carry out a precipitation reaction at 50 - 90 °C for 0.5 - 3 h to obtain a lithium product and a mother liquor for lithium precipitation;

[0062] Among them, the molar ratio of lithium in the lithium-rich solution to sodium carbonate is 1:(0.5 - 1), and the lithium product is a lithium carbonate product;

[0063] (V) Adjust the pH value of the lithium precipitation mother liquor to <2 with an acid, then mix it with the stripping raffinate, and perform a stripping treatment of Fe 3+ to obtain a solution rich in Fe 3+ ;

[0064] (VI) Mix the solution rich in Fe 3+ with the raffinate obtained in step (2), adjust the chloride ion concentration of the mixed solution to >5 mol / L, adjust the redox potential of the mixed solution to >300 mV, and then return it to step (1) as the leaching agent solution for cyclic leaching.

[0065] The numerical ranges described in the present invention include not only the above-listed point values, but also any point values between the above numerical ranges not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the ranges.

[0066] Compared with the prior art, the present invention has the following beneficial effects:

[0067] The method provided by the present invention does not add strong acids or strong bases throughout the process, and the solution containing the leaching agent cations and the raffinate can be recycled, with no wastewater discharge; moreover, the process is environmentally friendly, can directly extract lithium without impurity removal, has a high lithium recovery rate, and the lithium concentration obtained by stripping is high, and the lithium product can be directly precipitated, with low energy consumption and low cost. Brief Description of the Drawings

[0068] Figure 1 It is a process flow diagram for recovering lithium from waste black powder of lithium iron phosphate batteries provided in Example 1 of the present invention. Detailed Embodiments

[0069] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0070] It should be noted that the waste black powder of lithium iron phosphate batteries used in the following embodiments is the same.

[0071] Example 1

[0072] This example provides a method for recovering lithium from waste black powder of lithium iron phosphate batteries. The process flow chart of the method is as Figure 1 shown, and the method includes the following steps:

[0073] (1) Stir and mix the waste black powder of lithium iron phosphate batteries and FeCl3 solution, while controlling the chloride ion concentration of the mixed solution to >5 mol / L, and then perform a 1-hour leaching treatment at 80 °C to obtain a leachate;

[0074] Among them, the molar ratio of LiFePO4 to FeCl3 in the waste lithium iron phosphate battery black powder is 1:1;

[0075] (2) Stir and mix the leaching solution, co-extractor and diluent, and perform extraction treatment to obtain a raffinate and an extraction solution containing Li + , Fe 3+ ;

[0076] Among them, the volume ratio of the leaching solution to the co-extractor is 1:1. The co-extractor includes a neutral phosphine extractant and an acidic phosphine extractant with a volume ratio of 1:1. The neutral phosphine extractant is tributyl phosphate, and the acidic phosphine extractant is bis(2-ethylhexyl) phosphate. The diluent is 260# solvent oil. The volume ratio of the co-extractor to the diluent is 1:2. The extraction treatment method is a 5-stage multi-stage countercurrent method;

[0077] (3) Mix the extraction solution containing Li + , Fe 3+ with a stripping agent, and perform stripping treatment of Li + to obtain a lithium-rich solution and a stripping raffinate;

[0078] Among them, the stripping agent is HCl, and the volume ratio of the extraction solution to the stripping agent is 1:0.05. The stripping treatment method is a 5-stage multi-stage countercurrent method;

[0079] (4) Mix the lithium-rich solution and sodium carbonate, and perform a precipitation reaction at 80 °C for 2 h to obtain a lithium carbonate product and a mother liquor for lithium precipitation;

[0080] Among them, the molar ratio of lithium in the lithium-rich solution to sodium carbonate is 1:1.5;

[0081] (5) Adjust the pH value of the mother liquor for lithium precipitation to <2 with hydrochloric acid, then mix it with the stripping raffinate, and perform stripping treatment of Fe 3+ to obtain a Fe-rich 3+ solution;

[0082] (6) Mix the Fe-rich 3+ solution with the raffinate in step (2), and adjust the chloride ion concentration of the mixed solution to >5 mol / L by supplementing ferric chloride, and adjust the redox potential of the mixed solution to >300 mV, then return it to step (1) as a leaching agent solution for cyclic leaching.

[0083] Example 2

[0084] This example provides a method for recovering lithium from waste lithium iron phosphate battery black powder, and the method includes the following steps:

[0085] (1) Stir and mix the waste black powder of lithium iron phosphate battery and the leaching agent solution, while controlling the chloride ion concentration of the mixed solution to be > 5 mol / L, and then carry out leaching treatment at 50 °C for 2 h to obtain a leaching solution;

[0086] Among them, the leaching agent in the leaching agent solution includes FeCl3 and KCl, and their molar ratio is 1:2.5. The molar ratio of LiFePO4 in the waste black powder of lithium iron phosphate battery to the leaching agent is 1:0.5;

[0087] (2) Stir and mix the leaching solution, the synergistic extractant and the diluent, and carry out extraction treatment to obtain a raffinate and an extraction solution containing Li + , K + , Fe 3+ ;

[0088] Among them, the volume ratio of the leaching solution to the synergistic extractant is 1:3. The synergistic extractant includes a neutral phosphine extractant and an acidic phosphine extractant with a volume ratio of 0.5:1. The neutral phosphine extractant is tributyl phosphate, and the acidic phosphine extractant is 2-ethylhexyl 2-ethylhexyl phosphate. The diluent is n-heptane C7H 16 , and the volume ratio of the synergistic extractant to the diluent is 0.5:3. The extraction treatment method is a 5-stage multi-stage countercurrent method;

[0089] (3) Mix the extraction solution containing Li + , K + , Fe 3+ with the stripping agent, and carry out stripping treatment of Li + to obtain a lithium-rich solution and a stripping raffinate;

[0090] Among them, the stripping agent is HCl, and the volume ratio of the extraction solution to the stripping agent is 1:0.5. The stripping treatment method is a 5-stage multi-stage countercurrent method;

[0091] (4) Mix the lithium-rich solution and sodium carbonate, and carry out a precipitation reaction at 50 °C for 3 h to obtain a lithium carbonate product and a mother liquor for lithium precipitation;

[0092] Among them, the molar ratio of lithium in the lithium-rich solution to sodium carbonate is 1:1;

[0093] (5) Adjust the pH value of the mother liquor for lithium precipitation to < 2 with hydrochloric acid, and then mix it with the stripping raffinate to carry out stripping treatment of Fe 3+ and K + to obtain a solution rich in K + and Fe 3+ ;

[0094] (6) The rich K + and Fe 3+Mix the solution with the raffinate described in step (2), and adjust the chloride ion concentration of the mixed solution to > 5 mol / L by supplementing potassium chloride. Adjust the redox potential of the mixed solution to > 300 mV, and then return it to step (1) as the leaching agent solution for cyclic leaching.

[0095] Example 3

[0096] This example provides a method for recovering lithium from waste black powder of lithium iron phosphate batteries. The method includes the following steps:

[0097] (1) Stir and mix the waste black powder of lithium iron phosphate batteries with the leaching agent solution, while controlling the chloride ion concentration of the mixed solution to > 5 mol / L, and then carry out leaching treatment at 30 °C for 3 h to obtain a leaching solution;

[0098] Among them, the leaching agent in the leaching agent solution includes FeCl3 and AlCl3, and their molar ratio is 1:1. The molar ratio of LiFePO4 to the leaching agent in the waste black powder of lithium iron phosphate batteries is 1:1.5;

[0099] (2) Stir and mix the leaching solution, the synergistic extractant and the diluent, and carry out extraction treatment to obtain a raffinate and an extraction solution containing Li + , Al 3+ , Fe 3+ ;

[0100] Among them, the volume ratio of the leaching solution to the synergistic extractant is 1:5. The synergistic extractant includes a neutral phosphine extractant and an acidic phosphine extractant with a volume ratio of 0.25:1. The neutral phosphine extractant is tributyl phosphate, and the acidic phosphine extractant is bis(2-ethylhexyl) phosphate. The diluent is C9H 12 , and the volume ratio of the synergistic extractant to the diluent is 1:1. The extraction treatment method is a 5-stage multi-stage countercurrent method;

[0101] (3) Mix the extraction solution containing Li + , Al 3+ , Fe 3+ with the stripping agent, and carry out Li + stripping treatment to obtain a lithium-rich solution and a stripping raffinate;

[0102] Among them, the stripping agent is HCl, and the molar ratio of the extraction solution to the stripping agent is 1:1. The stripping treatment method is a 5-stage multi-stage countercurrent method;

[0103] (4) Mix the lithium-rich solution with sodium carbonate, and carry out a precipitation reaction at 90 °C for 0.5 h to obtain lithium carbonate products and a mother liquor for lithium precipitation;

[0104] Among them, the molar ratio of lithium in the lithium-rich solution to sodium carbonate is 1:0.5;

[0105] (5) Adjust the pH value of the mother liquor for lithium precipitation to <2 with hydrochloric acid, then mix it with the raffinate from stripping, and conduct the stripping treatment of Al 3+ and Fe 3+ to obtain a solution rich in Al 3+ and Fe 3+ ;

[0106] (6) Mix the solution rich in Al 3+ and Fe 3+ with the raffinate in step (2), and adjust the chloride ion concentration of the mixed solution to >5 mol / L by supplementing aluminum chloride, adjust the redox potential of the mixed solution to >300 mV, and then return it to step (1) as the leaching agent solution for cyclic leaching.

[0107] Example 4

[0108] The difference between this example and Example 1 is that in step (2), the volume ratio of the leaching solution to the synergistic extractant is 1:6.

[0109] The remaining methods and parameters are the same as those in Example 1.

[0110] Example 5

[0111] The difference between this example and Example 1 is that in step (2), the volume ratio of the leaching solution to the synergistic extractant is 1:0.2.

[0112] The remaining methods and parameters are the same as those in Example 1.

[0113] Example 6

[0114] The difference between this example and Example 1 is that in step (2), the volume ratio of the neutral phosphine extractant to the acidic phosphine extractant is 0.2:1.

[0115] The remaining methods and parameters are the same as those in Example 1.

[0116] Example 7

[0117] The difference between this example and Example 1 is that in step (2), the volume ratio of the neutral phosphine extractant to the acidic phosphine extractant is 1.5:1.

[0118] The remaining methods and parameters are the same as those in Example 1.

[0119] Example 8

[0120] The difference between this example and Example 1 is that in step (2), the synergistic extractant only contains a neutral phosphine extractant.

[0121] The remaining methods and parameters are the same as those in Example 1.

[0122] Example 9

[0123] The difference between this example and Example 1 is that the synergistic extractant described in step (2) contains only acidic phosphine extractants.

[0124] The remaining methods and parameters are the same as those in Example 1.

[0125] Example 10

[0126] The difference between this example and Example 1 is that the volume ratio of the synergistic extractant to the diluent in step (2) is 0.5:3.5.

[0127] The remaining methods and parameters are the same as those in Example 1.

[0128] Example 11

[0129] The difference between this example and Example 1 is that the volume ratio of the synergistic extractant to the diluent in step (2) is 1:0.5.

[0130] The remaining methods and parameters are the same as those in Example 1.

[0131] Example 12

[0132] The difference between this example and Example 1 is that the volume ratio of the extraction liquid to the stripping agent in step (3) is 1:1.5.

[0133] The remaining methods and parameters are the same as those in Example 1.

[0134] Example 13

[0135] The difference between this example and Example 1 is that the volume ratio of the extraction liquid to the stripping agent in step (3) is 1:0.02.

[0136] The remaining methods and parameters are the same as those in Example 1.

[0137] Comparative Example 1

[0138] The difference between this comparative example and Example 1 is that step (2) is not carried out.

[0139] The remaining methods and parameters are the same as those in Example 1.

[0140] Performance Test

[0141] The lithium content in the black powder of waste lithium iron phosphate batteries was detected by inductively coupled plasma optical emission spectrometry. It was found that the lithium content in the black powder was 3.5 g. The lithium content in the lithium products obtained from the above examples and comparative examples was detected, and then the lithium recovery rate was calculated. In addition, the purity of the lithium products was detected by titration.

[0142] The above test results are shown in Table 1 below.

[0143] Table 1

[0144]

[0145]

[0146] Analysis:

[0147] As can be seen from the above table, in the method provided by the present invention, strong acids and strong bases are not added throughout the process, and the solution containing the leaching agent cations and the raffinate can be recycled, with no wastewater discharge. Moreover, this process is environmentally friendly, can directly extract lithium without impurity removal, has a high lithium recovery rate, and the lithium concentration obtained by stripping is high, and lithium products can be directly precipitated, with low energy consumption and low cost.

[0148] As can be seen from Example 1 and Examples 4-5, if the volume ratio of the leaching solution to the synergistic extractant is too small, it will lead to waste of the extractant, high impurity extraction rate, and low product quality; if the molar ratio of the leaching solution to the synergistic extractant is too large, it will lead to low lithium extraction rate.

[0149] As can be seen from Example 1 and Examples 6-7, if the volume ratio of the neutral phosphine extractant to the acidic phosphine extractant is too small, it will lead to a high impurity extraction rate and low purity of the lithium product; if the volume ratio of the neutral phosphine extractant to the acidic phosphine extractant is too large, it will lead to low lithium extraction rate and low recovery rate.

[0150] As can be seen from Example 1 and Examples 8-9, if the synergistic extractant only contains a neutral phosphine extractant, it will lead to difficult stripping and high impurity content; if the synergistic extractant only contains an acidic phosphine extractant, it will lead to low lithium recovery rate.

[0151] As can be seen from Example 1 and Examples 10-11, if the volume ratio of the phosphine extractant to the diluent is too small, that is, the amount of the diluent is too large, it will lead to low lithium extraction rate; if the volume ratio of the phosphine extractant to the diluent is too large, that is, the amount of the diluent is too small, it will lead to a large viscosity of the extraction system, a large amount of entrained impurities, and low product quality.

[0152] As can be seen from Example 1 and Examples 12-13, if the volume ratio of the extraction solution to the stripping agent is too small, it will lead to high impurity content; if the volume ratio of the extraction solution to the stripping agent is too large, it will lead to incomplete stripping of lithium and low recovery rate.

[0153] As can be seen from Example 1 and Comparative Example 1, if step (2) is not carried out, it will lead to the inability to recover lithium and the difficulty in separating lithium from impurities.

[0154] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of the raw materials selected for the present invention, the addition of auxiliary components, the selection of specific methods, etc. all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for recovering lithium from waste black powder of lithium iron phosphate batteries, characterized in that, The method comprises the following steps: (1) Mix the black powder of waste lithium iron phosphate batteries and the leaching agent solution, and perform leaching treatment to obtain a leachate; (2) Mix the leaching solution with the synergistic extractant and perform extraction treatment to obtain a raffinate and an extract containing Li + and the cations of the leaching agent in the extract; (3) Stepwise back-extraction is performed on the extraction solution containing Li + and the leaching agent cations to obtain a lithium product and a solution containing the leaching agent cations; Among them, the leaching agent in the leaching agent solution includes FeCl3.

2. The method according to claim 1, wherein The molar ratio of LiFePO4 in the black powder of waste lithium iron phosphate batteries in step (1) to the leaching agent in the leaching agent solution is 1:(0.5 - 1.5); Preferably, the leaching agent in the leaching agent solution in step (1) further includes any one or a combination of at least two of NaCl, KCl, HCl, MgCl2, CaCl2 or AlCl3.

3. The method according to claim 1 or 2, characterized in that, During the leaching treatment in step (1), the chloride ion concentration of the mixed solution > 5 mol / L; Preferably, the temperature of the leaching treatment in step (1) is 30 - 80 °C, and the time is 0.5 - 3 h.

4. The method according to any one of claims 1 to 3, characterized in that, The co-extraction agent in step (2) includes a neutral phosphine extractant and an acidic phosphine extractant; Preferably, the volume ratio of the neutral phosphine extractant to the acidic phosphine extractant is (2 - 0.25):1; Preferably, the neutral phosphine extractant includes any one or a combination of at least two of tributyl phosphate, tri-sec-butyl phosphate, triamyl phosphate, tri-isoamyl phosphate or dimethylheptyl methylphosphonate; Preferably, the acidic phosphine extractant includes any one or a combination of at least two of bis(2-ethylhexyl) phosphate, 2-ethylhexyl 2-ethylhexyl phosphate, bis(2,2,4-trimethylpentyl) phosphinic acid or 2-ethylhexyl phosphinic acid; Preferably, a diluent is further added during the mixing process in step (2); Preferably, the volume ratio of the co-extraction agent to the diluent in step (2) is (1 - 0.5):(1 - 3); Preferably, the diluent includes hydrocarbons and / or alcohol compounds; Preferably, the number of carbon atoms in the hydrocarbons is 7 - 17.

5. The method according to any one of claims 1-4, characterized in that, The volume ratio of the leachate to the co-extraction agent in step (2) is 1:(0.25 - 5); Preferably, the extraction treatment method in step (2) includes a multi-stage countercurrent method, and the number of stages of the multi-stage countercurrent method is 2 - 8 stages.

6. The method according to any one of claims 1-5, characterized in that The specific steps of the stepwise stripping include: (a) Mix the extraction solution containing Li + , the cations of the leaching agent and the stripping agent, and perform the stripping treatment of Li + to obtain a lithium-rich solution and a stripping raffinate; (b) Mix the lithium-rich solution and the precipitant, and perform a precipitation reaction to obtain a lithium product and a mother liquor after lithium precipitation; (c) Adjust the pH value of the mother liquor after lithium precipitation < 2, and then mix it with the stripping raffinate to perform a stripping treatment of the leaching agent cations to obtain a solution containing leaching agent cations; (d) Mix the solution containing leaching agent cations and the raffinate, adjust the composition and then return to step (1) as the leaching agent solution for cyclic leaching.

7. The method according to claim 6, wherein The stripping agent in step (a) includes any one or a combination of at least two of HCl, NaCl, KCl or LiCl; Preferably, the volume ratio of the extract to the stripping agent in step (a) is 1:(0.05 - 1); Preferably, the stripping treatment method in step (a) includes a multi-stage countercurrent method, and the number of stages of the multi-stage countercurrent method is 2 - 8 stages.

8. The method according to claim 6 or 7, characterized in that, The precipitant in step (b) includes sodium carbonate; Preferably, the molar ratio of lithium in the lithium-rich solution to the precipitant in step (b) is 1:(0.5 - 1.5); Preferably, the temperature of the precipitation reaction in step (b) is 50 - 90 °C, and the time is 0.5 - 3 h.

9. The method according to any one of claims 6-8, characterized in that, The pH regulator for adjusting the pH value of the mother liquor for lithium precipitation in step (c) is an acid, and the acid includes sulfuric acid and / or hydrochloric acid; Preferably, the method for adjusting the composition in step (d) includes adjusting the chloride ion concentration of the mixed solution > 5 mol / L and adjusting the redox potential of the mixed solution > 300 mV; Preferably, the method for adjusting the redox potential of the mixed solution includes adding an oxidizing agent.

10. The method according to any one of claims 1-9, characterized in that, The method includes the following steps: (Ⅰ) Mix the waste black powder of lithium iron phosphate battery and the leaching agent solution containing FeCl3, and at the same time control the chloride ion concentration of the mixed solution > 5 mol / L, and then carry out leaching treatment at 30 - 80 °C for 0.5 - 3 h to obtain a leaching solution; Among them, the molar ratio of LiFePO4 to FeCl3 in the waste black powder of lithium iron phosphate battery is 1:(0.5 - 1.5); (II) Mix the leaching solution, the synergistic extractant and the diluent, and perform extraction treatment to obtain a raffinate and an extract containing Li + , Fe 3 + ; Among them, the volume ratio of the leaching solution to the synergistic extractant is 1:(0.25 - 5), the synergistic extractant includes a neutral phosphine extractant and an acidic phosphine extractant with a volume ratio of (2 - 0.25):1, and the volume ratio of the synergistic extractant to the diluent is (1 - 0.5):(1 - 3); (III) Mix the extraction solution containing Li + , Fe 3+ with the stripping agent for the stripping treatment of Li + to obtain a lithium-rich solution and a stripping raffinate; Among them, the volume ratio of the extract to the stripping agent is 1:(0.05 - 1); (Ⅳ) Mix the lithium-rich solution and sodium carbonate, and carry out a precipitation reaction at 50 - 90 °C for 0.5 - 3 h to obtain a lithium product and a mother liquor for lithium precipitation; Among them, the molar ratio of lithium to sodium carbonate in the lithium-rich solution is 1:(0.5 - 1), and the lithium product is a lithium carbonate product; (V) Adjust the pH value of the lithium precipitation mother liquor to < 2 with an acid, and then mix it with the stripping raffinate for stripping treatment of Fe 3+ to obtain a solution rich in Fe 3+ ; (Ⅵ) Mix the Fe-rich 3+ solution with the raffinate obtained in step (2), adjust the chloride ion concentration of the mixed solution to be > 5 mol / L, adjust the redox potential of the mixed solution to be > 300 mV, and then return it to step (1) as the leaching agent solution for cyclic leaching.

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