A method for co-disposing waste phosphoric acid etching solution and retired LiFePO4 power batteries

Abstract

The present invention discloses a method for co-disposing waste phosphoric acid etching solution and retired LiFePO4 power batteries. The method includes the following steps: enhanced leaching, purification and impurity removal, upgrading by bipolar membrane electrodialysis in a double desalination chamber, and mixed batching and cyclic regeneration. Compared with traditional recycling technologies, the present invention uses waste phosphoric acid etching solution from the optoelectronic industry to enhance the leaching of black powder from retired LiFePO4 power batteries, achieving the effect of coupling and disposing two kinds of waste in a recycling process. Through upgrading and transformation by bipolar membrane electrodialysis with a double desalination chamber structure, high-value recycled materials are obtained, realizing the purpose of recycling waste resources in the new energy field. The present invention has the characteristics of short process flow, high comprehensive resource utilization rate, low energy consumption and disposal cost, etc.

Description

Technical field:

[0001] The invention relates to the technical field of coordinated disposal of wastes in the optoelectronic industry and the new energy power lithium battery industry, and in particular to a method for coordinated disposal of waste phosphoric acid etching liquid and retired LiFePO4 power batteries. Background technology:

[0002] In recent years, with the rapid development of my country's new energy industry, the large-scale explosive production of electronic products such as thin-film transistor liquid crystal displays (TFT-LCD) and new energy vehicle power batteries has been stimulated. The rapid economic development has brought huge market demand, and environmental pollution problems have followed. The most noteworthy is that the TFT-LCD production process produces a large amount of waste phosphoric acid etching liquid, and the retired LiFePO4 power batteries produced after the scrapping of new energy. These two types of waste not only have certain environmental safety risks, but are also rich in a large number of strategic element phosphorus resources. In the context of the increasing scarcity of natural resources, the dual carbon strategy, the circular economy and sustainable development, how to achieve their safe disposal and resource recovery has become a difficult problem that needs to be solved in the development of the industry, and is becoming a research hotspot in the field of new energy.

[0003] Waste phosphoric acid etching liquid is a highly acidic hazardous waste produced in the wet etching process of TFT-LCD production, which is composed of phosphoric acid (30-80%), nitric acid (0.3-10%), acetic acid (1-20%) and a small amount of aluminum impurities. According to statistics, my country produces about 30,000 tons of waste phosphoric acid etching liquid every year, which is rich in phosphoric acid. Improper disposal not only leads to eutrophication of water bodies, posing a huge threat to the environment and human body, but also greatly wastes phosphorus resources. At present, the disposal of waste phosphoric acid etching liquid mainly involves neutralization with alkali solution or physical concentration and recovery of phosphoric acid. Publication No. CN114275750A discloses a method for recycling waste etching liquid in the optoelectronic industry. First, nitric acid and acetic acid are separated by negative pressure distillation to increase the concentration of phosphoric acid, and then sodium carbonate and sodium hydroxide are used for neutralization and precipitation to obtain products such as disodium hydrogen phosphate and sodium nitrate. Publication No. CN103979509A discloses a method for recovering phosphoric acid in waste aluminum etching liquid, and proposes to obtain phosphoric acid products by distillation, concentration, recrystallization, etc. Publication No. CN113264513A considers the interference of heavy metal ions, removes light components such as acetic acid and nitric acid in the waste etching liquid in a stripping tower after adding a metal precipitant to remove impurities, and then distills in a thin film evaporator to obtain a phosphoric acid product. Although the above methods can achieve safe disposal of waste phosphoric acid etching liquid, a large amount of low-concentration phosphorus-containing wastewater is generated in the recovery process, which has the potential risk of causing greater phosphorus pollution. It is urgent to develop a new method for low-cost and high-value utilization.

[0004] Retired lithium iron phosphate (LiFePO4) power batteries are a type of multi-component organic-inorganic composite solid waste generated after the scrapping of new energy electric vehicles. From 2020 to 2025, the first explosion period of retired LiFePO4 power batteries in China will occur. According to incomplete statistics, by 2025, the total amount of retired LiFePO4 power batteries in China will reach 950,000 tons. A large amount of strategic metals such as Li, Fe, P, graphite and toxic elements are enriched in them. How to realize their resource recycling has attracted extensive attention and research. At present, the main recycling method is to pre-treat them by discharging, disassembling, crushing and screening to obtain the positive and negative electrode materials, and then use wet methods (acid, alkali, salt and other systems), pyrometallurgy (oxidative roasting) or heat treatment (carbothermal reduction, vacuum pyrolysis) and other methods to separate and extract components such as lithium salts and iron salts. Industrial-grade chemical reagents are often used alone in the recycling process, increasing the treatment cost.

[0005] Based on the above analysis, the existing research has not paid attention to the common properties of waste phosphoric acid etching solution and retired LiFePO4 power batteries. Instead, they are treated separately as two unrelated wastes. Moreover, the existing recycling processes do not have the possibility of co-disposing these two wastes. Therefore, it is necessary to develop a new process to solve the problem of co-disposing waste phosphoric acid etching solution and retired LiFePO4 power batteries. How to achieve the common coupling of these two wastes and realize the treatment / consumption of one waste by another waste to obtain high-value recycled products has become an urgent problem to be solved in the field of waste disposal in the optoelectronic industry and the new energy power lithium battery industry. Summary of the Invention:

[0006] The present invention solves the problems existing in the prior art and provides a method for co-disposing waste phosphoric acid etching solution and retired LiFePO4 power batteries. The present invention uses the waste phosphoric acid etching solution in the optoelectronic industry as a phosphoric acid leaching agent to intensively leach the black powder of retired LiFePO4 power batteries. Compared with the traditional oxidative roasting conventional process, it avoids the forced purification and separation of the positive / negative electrode materials in the black powder by using high-energy-consuming and highly polluting pyrometallurgy. At the same time, it solves the problem of phosphorus pollution in the phosphorus-containing wastewater in the optoelectronic industry, and can simultaneously achieve the dual effects of intensive decomposition and high-value utilization of LiFePO4 and safe and environmentally friendly disposal of waste phosphoric acid etching solution, with huge economic, environmental and resource benefits.

[0007] The purpose of the present invention is to provide a method for co-disposing waste phosphoric acid etching solution and retired LiFePO4 power batteries, including the following steps:

[0008] (1) Enhanced leaching: The black powder obtained by crushing and sorting retired LiFePO4 power batteries is ball-milled. After mixing the waste phosphoric acid etching solution diluted with deionized water and the ball-milled black powder at a volume-to-mass ratio of 1:10 - 1:20 mL / g, mechanical stirring enhanced leaching reaction is carried out under the action of a strengthening agent. After the enhanced leaching reaction is completed, vacuum is pumped to separate the liquid and solid to obtain FePO4 / graphite powder and lithium-rich leaching solution. The FePO4 / graphite powder enters the step (4) of mixing and batching for recycling process;

[0009] (2) Purification and impurity removal: Add a purification precipitant to the lithium-rich leaching solution obtained in step (1) for purification and impurity removal to obtain metal precipitates containing copper and aluminum and lithium-rich purified solution. The metal precipitates are returned to the copper-aluminum smelting process for further utilization;

[0010] (3) Double desalination chamber electrodialysis for quality improvement: The lithium-rich purified solution obtained in step (2) is subjected to bipolar membrane electrodialysis for quality improvement to obtain regenerated LiOH, regenerated phosphoric acid and lean solution. The regenerated LiOH enters the step (4) of mixing and batching for recycling process, the regenerated phosphoric acid is used for the etching process in the production of TFT-LCD in the optoelectronic industry, and the lean solution is returned to the step (1) of enhanced leaching process for further utilization;

[0011] (4) Mixing, batching and recycling: Mix the FePO4 / graphite powder obtained in step (1) with the regenerated LiOH obtained in step (3) for mixing, batching and recycling to prepare LiFePO4 / C.

[0012] Preferably, the specific steps of ball-milling the black powder obtained by crushing and sorting the retired LiFePO4 power batteries in step (1) are: The black powder obtained by disassembling, crushing and sorting or heat treatment crushing and sorting of the retired LiFePO4 power batteries is ball-milled to a particle size of 180 - 200 mesh.

[0013] Preferably, in the enhanced leaching process of step (1), the waste phosphoric acid etching solution is derived from the waste phosphoric acid generated in the etching process of TFT-LCD production in the optoelectronic industry. The phosphoric acid content of the waste phosphoric acid etching solution is 20 - 75 wt%, the impurity aluminum content is 0.001 - 1.2 g / L, and the waste phosphoric acid etching solution is diluted with deionized water to a phosphoric acid concentration of 0.5 - 1.2 mol / L.

[0014] Preferably, the strengthening agent in step (1) includes at least one of H2O2 and active oxygen.

[0015] In step (1), the waste phosphoric acid etching solution provides an acidic condition, and LiFePO4 is decomposed to generate Li + , Fe 2+ , PO4 3- . At this time, Fe 2+ is further oxidized by the added strengthening agent hydrogen peroxide or active oxygen to Fe 3+ , and the generated Fe3+ With PO4 3- The insoluble FePO4 precipitate is generated and co-precipitated after being mixed with inert graphite. The reaction process is shown in Equation (1):

[0016] LiFePO4 + H2O2 / O2 + H3PO4 → Li + + FePO4 (precipitate) + O4 3- + H2O (1)

[0017] Preferably, the reaction temperature of the enhanced leaching reaction described in step (1) is 25°C to 55°C, and the reaction time is 60 to 180 min.

[0018] Preferably, the purification precipitant described in step (2) is the regenerated LiOH produced in step (3), which is used to adjust the pH of the lithium-rich purification liquid to 4.8 to 5.2. When the method is just started, the commercially available LiOH can be used as the purification precipitant. After the regenerated LiOH is produced in step (3), the regenerated LiOH obtained in step (3) is used.

[0019] Preferably, in the double desalination chamber electrodialysis quality improvement process described in step (3), in order to improve work efficiency and save energy consumption, a bipolar membrane electrodialysis device adopts a structure design of double desalination chambers, double alkali chambers and double acid chambers. Among them, the anode plate (AN) and the bipolar membrane (BPM) form the anode chamber, the cathode plate (CN) and the bipolar membrane (BPM) form the cathode chamber, the bipolar membrane (BPM) and the cation exchange membrane (CEM) form the alkali chamber, the cation exchange membrane (CEM) and the anion exchange membrane (AEM) form the desalination chamber, and the bipolar membrane (BPM) and the anion exchange membrane (AEM) form the acid chamber. Before work, the desalination chamber pumps in the lithium-rich purification liquid, the acid chamber pumps in the H3PO4 solution as the initial acid solution, the alkali chamber pumps in the LiOH solution as the initial alkali solution, and the anode chamber and the cathode chamber both pump in the LiH2PO4 solution as the electrode solution. Direct current is passed through the anode plate and the cathode plate to start working. During the working process, the double desalination chambers, double alkali chambers, double acid chambers, anode chamber and cathode chamber all circulate at a constant speed of 0.8 L / min through the circulation pump until the reaction ends.

[0020] Preferably, in the double desalination chamber electrodialysis quality improvement process described in step (3), the cation exchange membrane used in the bipolar membrane electrodialysis device is at least one of the monovalent selective cation exchange membrane Aciplex A-192 and CMS, and the anion exchange membrane adopts AMX. The concentration of the electrode solution LiH2PO4 solution is 1.0 to 1.5 mol / L, the concentration of the initial acid solution H3PO4 solution is 0.01 to 0.03 mol / L, and the concentration of the initial alkali solution LiOH solution is 0.03 to 0.09 mol / L.

[0021] Preferably, in the process of cyclic regeneration of the mixed ingredients in step (4), FePO4 / graphite powder and regenerated LiOH are mixed at a molar ratio of Fe to Li of 1:1 to 1:5, thermally reduced for 1.5 to 3.5 h under a carbon dioxide protection atmosphere, and the thermal reduction temperature is 500 °C to 950 °C to obtain LiFePO4 / C.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] 1. The present invention uses waste phosphoric acid etching solution in the optoelectronic industry as a phosphoric acid leaching agent to intensively leach black powder of retired LiFePO4 power batteries. Compared with the traditional oxidation roasting conventional process, it avoids the forced purification and separation of the positive / negative electrode materials in the black powder by using high-energy-consuming and highly polluting pyrometallurgy. At the same time, it solves the phosphorus pollution problem of phosphorus-containing wastewater in the optoelectronic industry, and can simultaneously achieve the dual effects of intensive deconstruction and high-value utilization of LiFePO4 and safe and environmentally friendly disposal of waste phosphoric acid etching solution. In addition, using waste phosphoric acid etching solution (recovery value: about 3,500 yuan / ton) instead of industrial phosphoric acid (market value: about 10,000 yuan / ton) can save the recovery cost, and the organic components such as acetic acid in the waste phosphoric acid etching solution can be used to dissolve the remaining organic impurities such as diaphragms in the black powder, avoiding the interference of impurity components on the leaching process of valuable elements, and having great economic, environmental and resource benefits.

[0024] 2. The present invention uses the bipolar membrane electrodialysis technology with a double desalination chamber to replace the traditional neutralization precipitation and extraction and back-extraction lithium extraction process, avoiding the discharge of tail liquid and realizing the cyclic regeneration of valuable components. In addition, the bipolar membrane electrodialysis device with a double desalination chamber structure design has a double desalination chamber, a double alkali chamber, and a double acid chamber. Compared with the traditional single desalination chamber structure design, it can realize the internal cyclic flow of raw materials and products in the desalination chamber, the alkali chamber, and the acid chamber, ensuring its concentration balance, improving the current efficiency, and having the characteristics of low energy consumption and high disposal efficiency. Using a univalent selective cation exchange membrane instead of the traditional non-selective cation exchange membrane can effectively avoid the interference of high-valent cations on univalent lithium ions, improve the separation efficiency, and increase the service life of the ion exchange membrane.

[0025] 3. The present invention is particularly suitable for disposing of waste phosphoric acid etching solution generated in the wet etching process of TFT-LCD production in the optoelectronic industry and black powder generated by heat treatment, crushing and sorting of retired LiFePO4 power batteries in the new energy field. The two kinds of wastes are coupled in common, not only realizing the high-value recycling of valuable components in the black powder of retired LiFePO4 power batteries, but also saving the waste acid treatment cost in the optoelectronic industry, achieving the dual effects of "treating waste with waste", and having the characteristics of co-disposal, short process flow, high comprehensive resource utilization rate and low disposal cost. Description of the drawings:

[0026] Figure 1 is a flow chart of the source of black powder of retired LiFePO4 power batteries proposed by the present invention.

[0027] Figure 2 This is the process flow chart of the method for co - disposing waste phosphoric acid etching solution and retired LiFePO4 power batteries proposed by the present invention.

[0028] Figure 3 This is the schematic diagram of the bipolar membrane electrodialysis upgrading process with a double - desalination - chamber structure proposed by the present invention. Specific implementation manners:

[0029] The following embodiments are further descriptions of the present invention rather than limitations thereof.

[0030] Unless otherwise defined, all professional terms used hereinafter have the same meaning as commonly understood by those skilled in the art. The professional terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specified, the experimental materials and reagents in this article are all conventional commercially available products in this technical field.

[0031] As Figure 1 shown, the retired LiFePO4 power batteries are disassembled to separate the aluminum / copper current collector mixture, and then after crushing and sorting or directly through heat treatment followed by crushing and sorting, black powder is obtained.

[0032] As Figure 3 shown, the co - disposal of the waste phosphoric acid etching solution and the retired LiFePO4 power batteries is carried out in a bipolar membrane electrodialysis device with a double - desalination - chamber structure design. To improve work efficiency and save energy consumption, a double - desalination - chamber, double - alkali - chamber, and double - acid - chamber structure design is adopted. Among them, the anode plate (AN) and the bipolar membrane (BPM) form the anode chamber, the cathode plate (CN) and the bipolar membrane (BPM) form the cathode chamber, the bipolar membrane (BPM) and the cation - exchange membrane (CEM) form the alkali chamber, the cation - exchange membrane (CEM) and the anion - exchange membrane (AEM) form the desalination chamber, and the bipolar membrane (BPM) and the anion - exchange membrane (AEM) form the acid chamber. Before work, the desalination chamber is pumped with a lithium - rich purification solution, the acid chamber is pumped with an H3PO4 solution as the initial acid solution, the alkali chamber is pumped with a LiOH solution as the initial alkali solution, and both the anode chamber and the cathode chamber are pumped with a LiH2PO4 solution as the electrode solution. Direct current is passed through the anode plate and the cathode plate to start work. During the working process, the double - desalination chamber, double - alkali chamber, double - acid chamber, anode chamber, and cathode chamber all circulate at a constant speed of 0.8 L / min through a circulation pump until the reaction ends. The concentration of the initial acid solution H3PO4 solution is 0.01 - 0.03 mol / L, and the concentration of the initial alkali solution LiOH solution is 0.03 - 0.09 mol / L.

[0033] Example 1

[0034] As Figure 2As shown in the figure, a method for co - disposing waste phosphoric acid etching solution and retired LiFePO4 power batteries includes the following steps:

[0035] (1) Enhanced leaching: The black powder obtained by disassembling, crushing, sorting or heat - treating and crushing and sorting retired LiFePO4 power batteries is ball - milled to a particle size of 180 mesh. The waste phosphoric acid etching solution mainly from the etching process in the production of TFT - LCD in the optoelectronic industry, with a phosphoric acid content of 20% and an impurity aluminum content of 0.001 g / L, is diluted with deionized water to a phosphoric acid concentration of 0.5 mol / L. Then, the diluted waste phosphoric acid etching solution and the ball - milled black powder are mixed at a volume - to - mass ratio of 1:10 mL / g in an ultrasonic reactor, and mechanical stirring enhanced leaching is carried out under the action of H2O2 intensifier. The reaction is carried out at a reaction temperature of 55 °C for 60 min. After the leaching is completed, vacuum liquid - solid separation is carried out to obtain FePO4 / graphite powder and lithium - rich leaching solution. The FePO4 / graphite powder enters the mixed batching and recycling regeneration process of step (4);

[0036] (2) Purification and impurity removal: The lithium - rich leaching solution obtained in step (1) is added with the regenerated LiOH generated in step (3) as a purification precipitant for purification and impurity removal until the pH of the lithium - rich leaching solution is adjusted to 4.8, obtaining metal precipitates and lithium - rich purified solution. The metal precipitates are returned to the copper - aluminum smelting plant;

[0037] (3) Double - desalination - chamber electrodialysis for quality improvement: The lithium - rich purified solution obtained in step (2) is subjected to bipolar membrane electrodialysis for quality improvement. The bipolar membrane electrodialysis equipment used adopts a double - desalination - chamber structure design. The cation - exchange membrane used is a monovalent - selective cation - exchange membrane Aciplex A - 192, and the anion - exchange membrane adopts AMX. The concentration of the electrode solution LiH2PO4 solution is 1.0 mol / L, the concentration of the initial acid solution H3PO4 solution is 0.01 mol / L, and the concentration of the initial alkali solution LiOH solution is 0.03 mol / L. After the reaction, regenerated LiOH, regenerated phosphoric acid and lean solution are obtained. The regenerated LiOH enters the mixed batching and recycling regeneration process of step (4), the regenerated phosphoric acid is used for the etching process in the production of TFT - LCD in the optoelectronic industry, and the lean solution is returned to the enhanced leaching process;

[0038] (4) Mixed batching and recycling regeneration: The FePO4 / graphite powder obtained in step (1) and the regenerated LiOH obtained in step (3) are mixed for batching and recycling regeneration to prepare LiFePO4 / C. The FePO4 / graphite powder and the regenerated LiOH are mixed at an Fe:Li molar ratio of 1:1 and thermally reduced under a carbon dioxide - protected atmosphere for 1.5 h, and the thermal reduction temperature is 500 °C.

[0039] During the recycling process, the comprehensive lithium recovery rate is 98.9%, the comprehensive FePO4 recovery rate is 97.5%. The bipolar membrane electrodialysis with a double desalination chamber structure has 22.5% lower energy consumption and 17.6% higher current efficiency compared with the traditional single desalination chamber electrodialysis. The regenerated phosphoric acid produced can be recycled for etching in the production of TFT-LCD in the optoelectronic industry.

[0040] Example 2

[0041] As Figure 2 shown, a method for the collaborative treatment of waste phosphoric acid etching solution and retired LiFePO4 power batteries includes the following steps:

[0042] (1) Enhanced leaching: The black powder obtained by disassembling, crushing, sorting or heat-treating and crushing and sorting retired LiFePO4 power batteries is ball-milled to a particle size of 200 mesh. The waste phosphoric acid etching solution with a main component of phosphoric acid content of 75% and impurity aluminum content of 1.2 g / L generated during the etching process of TFT-LCD production in the optoelectronic industry is diluted with deionized water to a phosphoric acid concentration of 1.2 mol / L. Then, the diluted waste phosphoric acid etching solution and the ball-milled black powder are mixed at a volume-to-mass ratio of 1:20 mL / g in an ultrasonic reactor and mechanically stirred for enhanced leaching under the action of an active oxygen intensifier. The reaction is carried out at a reaction temperature of 25 °C for 180 min. After the leaching is completed, vacuum is applied for liquid-solid separation to obtain FePO4 / graphite powder and lithium-rich leaching solution. The FePO4 / graphite powder enters the step (4) of the mixed batching and recycling regeneration process;

[0043] (2) Purification and impurity removal: The lithium-rich leaching solution obtained in step (1) is added with the regenerated LiOH produced in step (3) as a purification precipitant for purification and impurity removal until the pH of the lithium-rich leaching solution is adjusted to 5.2, obtaining metal precipitates and lithium-rich purified solution. The metal precipitates are returned to the copper-aluminum smelter;

[0044] (3) Quality improvement by bipolar membrane electrodialysis in a double desalination chamber: The lithium-rich purified solution obtained in step (2) is subjected to quality improvement by bipolar membrane electrodialysis. The bipolar membrane electrodialysis equipment used adopts a double desalination chamber structure design. The cation exchange membrane used is a monovalent selective cation exchange membrane CMS, and the anion exchange membrane adopts AMX. The concentration of the electrode solution LiH2PO4 solution is 1.5 mol / L, the concentration of the initial acid solution H3PO4 solution is 0.03 mol / L, and the concentration of the initial alkali solution LiOH solution is 0.09 mol / L. After the reaction, regenerated LiOH, regenerated phosphoric acid and lean solution are obtained. The regenerated LiOH enters the step (4) of the mixed batching and recycling regeneration process, the regenerated phosphoric acid is used for the etching process in the production of TFT-LCD in the optoelectronic industry, and the lean solution is returned to the enhanced leaching process;

[0045] (4) Recycling of mixed ingredients in a cycle: The FePO4 / graphite powder obtained in step (1) and the recycled LiOH obtained in step (3) are mixed and recycled to prepare LiFePO4 / C. The FePO4 / graphite powder and the recycled LiOH are mixed at a molar ratio of Fe to Li of 1:5 and thermally reduced for 3.5 h under a carbon dioxide protection atmosphere at a thermal reduction temperature of 950 °C.

[0046] During the recovery process, the comprehensive lithium recovery rate is 99.3%, and the comprehensive FePO4 recovery rate is 98.2%. The bipolar membrane electrodialysis with a double desalination chamber structure has 26.1% lower energy consumption and 20.5% higher current efficiency compared to the traditional single desalination chamber electrodialysis. The regenerated phosphoric acid produced can be used for etching recycling in the production of TFT-LCD in the optoelectronic industry.

[0047] Example 3

[0048] As Figure 2 shown, a method for the collaborative disposal of waste phosphoric acid etching solution and retired LiFePO4 power batteries includes the following steps:

[0049] (1) Enhanced leaching: The black powder obtained by disassembling, crushing, sorting or heat-treating and crushing and sorting retired LiFePO4 power batteries is ball-milled to a particle size of 200 mesh. The waste phosphoric acid etching solution with a main component of phosphoric acid content of 30.5% and an impurity aluminum content of 0.01 g / L generated during the etching process of TFT-LCD production in the optoelectronic industry is diluted with deionized water to a phosphoric acid concentration of 0.7 mol / L. Then, the diluted waste phosphoric acid etching solution and the ball-milled black powder are mixed at a volume-mass ratio of 1:12 mL / g in an ultrasonic reactor and mechanically stirred for enhanced leaching under the action of an H2O2 intensifier. The reaction is carried out at a reaction temperature of 35 °C for 150 min. After the leaching is completed, vacuum is applied for liquid-solid separation to obtain FePO4 / graphite powder and lithium-rich leaching solution. The FePO4 / graphite powder enters the step (4) of recycling the mixed ingredients in a cycle;

[0050] (2) Purification and impurity removal: The lithium-rich leaching solution obtained in step (1) is added with the recycled LiOH generated in step (3) as a purification precipitant for purification and impurity removal until the pH of the lithium-rich leaching solution is adjusted to 4.9, obtaining metal precipitates and lithium-rich purified solution. The metal precipitates are returned to the copper-aluminum smelter;

[0051] (3) Quality improvement by bipolar membrane electrodialysis in a double desalination chamber: The lithium-rich purified solution obtained in step (2) is subjected to quality improvement by bipolar membrane electrodialysis. The bipolar membrane electrodialysis equipment used adopts a double desalination chamber structure design. The cation exchange membrane used is a monovalent selective cation exchange membrane Aciplex A-192, and the anion exchange membrane adopts AMX, the concentration of the electrode liquid LiH2PO4 solution is 1.1 mol / L, the concentration of the initial acid solution H3PO4 solution is 0.02 mol / L, the concentration of the initial alkali solution LiOH solution is 0.06 mol / L. After the reaction, regenerated LiOH, regenerated phosphoric acid and lean liquid are obtained. The regenerated LiOH enters the step (4) mixing and batching recycling regeneration process, the regenerated phosphoric acid is used for the etching process in the production of TFT-LCD in the optoelectronic industry, and the lean liquid returns to the enhanced leaching process;

[0052] (4) Mixing and batching recycling regeneration: Mix the FePO4 / graphite powder obtained in step (1) with the regenerated LiOH obtained in step (3) for mixing and batching recycling regeneration to prepare LiFePO4 / C. The FePO4 / graphite powder and the regenerated LiOH are mixed at a molar ratio of Fe to Li of 1:1.2 and thermally reduced under a carbon dioxide protection atmosphere for 1.6 h, and the thermal reduction temperature is 580 °C.

[0053] During the recovery process, the comprehensive lithium recovery rate is 98.7%, the comprehensive FePO4 recovery rate is 97.9%. The bipolar membrane electrodialysis with a double desalination chamber structure has 23.1% lower energy consumption and 19.0% higher current efficiency than the traditional single desalination chamber electrodialysis. The regenerated phosphoric acid produced can be used for the etching cycle in the production of TFT-LCD in the optoelectronic industry.

[0054] Example 4

[0055] As Figure 2 shown, a method for the collaborative treatment of waste phosphoric acid etching solution and retired LiFePO4 power batteries includes the following steps:

[0056] (1) Enhanced leaching: The black powder obtained by disassembling, crushing, sorting or heat-treating and crushing and sorting the retired LiFePO4 power batteries is ball-milled to a particle size of 195 mesh. The waste phosphoric acid etching solution with a main component of phosphoric acid content of 65% and impurity aluminum content of 0.85 g / L generated during the etching process in the production of TFT-LCD in the optoelectronic industry is diluted with deionized water to a phosphoric acid concentration of 1.1 mol / L. Then, the diluted waste phosphoric acid etching solution and the ball-milled black powder are mixed at a volume-mass ratio of 1:17 mL / g in an ultrasonic reactor, and mechanical stirring enhanced leaching is carried out under the action of an active oxygen intensifier. The reaction is carried out at a reaction temperature of 50 °C for 90 min. After the leaching is completed, vacuum liquid-solid separation is carried out to obtain FePO4 / graphite powder and lithium-rich leaching solution. The FePO4 / graphite powder enters the step (4) mixing and batching recycling regeneration process;

[0057] (2) Purification and impurity removal: Add the regenerated LiOH generated in step (3) as a purification precipitant to the lithium-rich leaching solution obtained in step (1) for purification and impurity removal until the pH of the lithium-rich leaching solution is adjusted to 5.1, obtaining metal precipitates and lithium-rich purified solution. The metal precipitates are returned to the copper-aluminum smelter;

[0058] (3) Double desalination chamber electrodialysis for quality improvement: The lithium-rich purified liquid obtained in step (2) is subjected to bipolar membrane electrodialysis for quality improvement. The bipolar membrane electrodialysis equipment used adopts a double desalination chamber structure design. The cation exchange membrane used is a monovalent selective cation exchange membrane CMS, and the anion exchange membrane adopts AMX. The concentration of the electrode solution LiH2PO4 solution is 1.4 mol / L, the concentration of the initial acid solution H3PO4 solution is 0.01 mol / L, and the concentration of the initial alkali solution LiOH solution is 0.03 mol / L. After the reaction, regenerated LiOH, regenerated phosphoric acid and lean liquid are obtained. The regenerated LiOH enters step (4) for the mixing and batching cyclic regeneration process, the regenerated phosphoric acid is used for the etching process in the production of TFT-LCD in the optoelectronic industry, and the lean liquid returns to the enhanced leaching process;

[0059] (4) Mixing, batching and cyclic regeneration: The FePO4 / graphite powder obtained in step (1) and the regenerated LiOH obtained in step (3) are mixed, batched and cyclically regenerated to prepare LiFePO4 / C. The FePO4 / graphite powder and the regenerated LiOH are mixed at a molar ratio of Fe to Li of 1:3 and thermally reduced under a carbon dioxide protection atmosphere for 3.0 h, and the thermal reduction temperature is 850 °C.

[0060] During the recovery process, the comprehensive lithium recovery rate is 99.0%, the comprehensive FePO4 recovery rate is 98.7%. The bipolar membrane electrodialysis with a double desalination chamber structure has 24.2% lower energy consumption and 19.4% higher current efficiency compared with the traditional single desalination chamber electrodialysis. The regenerated phosphoric acid produced can be used for the etching cycle in the production of TFT-LCD in the optoelectronic industry.

[0061] Example 5

[0062] As Figure 2 shown, a method for the collaborative treatment of waste phosphoric acid etching solution and retired LiFePO4 power batteries includes the following steps:

[0063] (1) Enhanced leaching: The black powder obtained by disassembling, crushing, sorting or heat-treating and crushing and sorting the retired LiFePO4 power batteries is ball-milled to a particle size of 185 mesh. The waste phosphoric acid etching solution with a main component of phosphoric acid content of 55% and impurity aluminum content of 0.28 g / L generated from the etching process in the production of TFT-LCD in the optoelectronic industry is diluted with deionized water to a phosphoric acid concentration of 0.85 mol / L. Then, the diluted waste phosphoric acid etching solution and the ball-milled black powder are mixed at a volume-mass ratio of 1:16 mL / g in an ultrasonic reactor and mechanically stirred and enhanced leached under the action of a hydrogen peroxide intensifier. The reaction is carried out at a reaction temperature of 30 °C for 120 min. After the leaching is completed, vacuum liquid-solid separation is carried out to obtain FePO4 / graphite powder and lithium-rich leaching solution. The FePO4 / graphite powder enters step (4) for the mixing and batching cyclic regeneration process;

[0064] (2) Purification and impurity removal: Add a purification precipitant to the lithium-rich leaching solution obtained in step (1) for purification and impurity removal. Use the regenerated LiOH produced in step (3) as a purification agent to adjust the pH of the lithium-rich leaching solution to 5.0 until a metal precipitate and a lithium-rich purified solution are obtained. The metal precipitate is returned to the copper-aluminum smelter;

[0065] (3) Double-desalination chamber electrodialysis for quality improvement: Perform bipolar membrane electrodialysis for quality improvement on the lithium-rich purified solution obtained in step (2). The bipolar membrane electrodialysis equipment used adopts a double-desalination chamber structure design. The cation exchange membrane used is a monovalent selective cation exchange membrane CMS, and the anion exchange membrane adopts AMX. The concentration of the electrode solution LiH2PO4 solution is 1.15 mol / L, the concentration of the initial acid solution H3PO4 solution is 0.015 mol / L, and the concentration of the initial alkali solution LiOH solution is 0.045 mol / L. After the reaction, regenerated LiOH, regenerated phosphoric acid, and lean solution are obtained. The regenerated LiOH enters step (4) for the mixed batching and recycling regeneration process. The regenerated phosphoric acid is used in the etching process for TFT-LCD production in the optoelectronic industry, and the lean solution is returned to the enhanced leaching process;

[0066] (4) Mixed batching and recycling regeneration: Mix the FePO4 / graphite powder obtained in step (1) with the regenerated LiOH obtained in step (3) for mixed batching and recycling regeneration to prepare LiFePO4 / C. The FePO4 / graphite powder and the regenerated LiOH are mixed at an Fe:Li molar ratio of 1:4 and thermally reduced under a carbon dioxide protection atmosphere for 2.5 h. The thermal reduction temperature is 750 °C.

[0067] During the recovery process, the comprehensive lithium recovery rate is 99.2%, the comprehensive FePO4 recovery rate is 98.1%. The bipolar membrane electrodialysis with a double-desalination chamber structure has 26.0% lower energy consumption and 20.3% higher current efficiency compared to the traditional single-desalination chamber electrodialysis. The regenerated phosphoric acid produced can be used for etching recycling in TFT-LCD production in the optoelectronic industry.

[0068] Example 6

[0069] As Figure 2 shown, a method for the collaborative treatment of waste phosphoric acid etching solution and retired LiFePO4 power batteries includes the following steps:

[0070] (1) Enhanced leaching: The black powder obtained by disassembling, crushing, sorting or heat-treating and crushing and sorting retired LiFePO4 power batteries is ball-milled to a particle size of 190 mesh. The waste phosphoric acid etching solution with a main component of phosphoric acid content of 46.3% and impurity aluminum content of 1.05 g / L generated from the etching process of TFT-LCD production in the optoelectronic industry is diluted with deionized water to a phosphoric acid concentration of 1.0 mol / L. Then, the diluted waste phosphoric acid etching solution and the ball-milled black powder are mixed at a volume-mass ratio of 1:14 mL / g in an ultrasonic reactor, and mechanical stirring enhanced leaching is carried out under the action of an active oxygen enhancer. The reaction is carried out at a reaction temperature of 40 °C for 100 min. After leaching, vacuum is pumped to separate the liquid and solid to obtain FePO4 / graphite powder and lithium-rich leaching solution. The FePO4 / graphite powder enters the step (4) of mixing, batching and recycling process;

[0071] (2) Purification and impurity removal: The lithium-rich leaching solution obtained in step (1) is added with a purification precipitant for purification and impurity removal. The regenerated LiOH generated in step (3) is used as a purification agent to adjust the pH of the lithium-rich leaching solution to 5.1, obtaining metal precipitates and lithium-rich purified solution. The metal precipitates are returned to the copper-aluminum smelter;

[0072] (3) Double desalination chamber electrodialysis for quality improvement: The lithium-rich purified solution obtained in step (2) is subjected to bipolar membrane electrodialysis for quality improvement. The bipolar membrane electrodialysis equipment used adopts a double desalination chamber structure design. The cation exchange membrane used is a monovalent selective cation exchange membrane Aciplex A-192, and the anion exchange membrane adopts AMX. The concentration of the electrode solution LiH2PO4 solution is 1.35 mol / L, the concentration of the initial acid solution H3PO4 solution is 0.025 mol / L, and the concentration of the initial alkali solution LiOH solution is 0.075 mol / L. After the reaction, regenerated LiOH, regenerated phosphoric acid and lean solution are obtained. The regenerated LiOH enters the step (4) of mixing, batching and recycling process. The regenerated phosphoric acid is used for the etching process of TFT-LCD production in the optoelectronic industry, and the lean solution is returned to the enhanced leaching process;

[0073] (4) Mixing, batching and recycling: The FePO4 / graphite powder obtained in step (1) and the regenerated LiOH obtained in step (3) are mixed, batched and recycled to prepare LiFePO4 / C. The FePO4 / graphite powder and the regenerated LiOH are mixed at an Fe:Li molar ratio of 1:3 and thermally reduced under a carbon dioxide protection atmosphere for 2.0 h. The thermal reduction temperature is 600 °C.

[0074] During the recovery process, the comprehensive lithium recovery rate is 98.6%, the comprehensive FePO4 recovery rate is 97.7%. The bipolar membrane electrodialysis with a double desalination chamber structure has 25.6% lower energy consumption and 20.4% higher current efficiency compared with the traditional single desalination chamber electrodialysis. The regenerated phosphoric acid produced can be used for the etching cycle of TFT-LCD production in the optoelectronic industry.

[0075] The description of the above embodiments is only used to help understand the technical solution and its core idea of the present invention. It should be noted that for those skilled in the art of this technology, without departing from the principle of the present invention, several improvements and modifications can still be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A method for co - disposing waste phosphoric acid etching solution and retired LiFePO4 power batteries, characterized in that, It includes the following steps: (1) Enhanced leaching: The black powder obtained by crushing and separating retired LiFePO4 power batteries is ball-milled. After mixing the waste phosphoric acid etching solution diluted with deionized water with the ball-milled black powder at a volume-mass ratio of 1:10 - 1:20 mL / g, mechanical stirring enhanced leaching reaction is carried out under the action of a strengthening agent. The reaction temperature of the enhanced leaching reaction is 25°C - 55°C, and the reaction time is 60 - 180 min. After the enhanced leaching reaction is completed, vacuum is pumped to separate the liquid and solid to obtain FePO4 / graphite powder and lithium-rich leaching solution. The FePO4 / graphite powder enters the step (4) of the mixed batching and recycling regeneration process. The waste phosphoric acid etching solution is derived from the waste phosphoric acid generated during the etching process of TFT-LCD production in the optoelectronic industry. The phosphoric acid content of the waste phosphoric acid etching solution is 20 - 75 wt%, the impurity aluminum content is 0.001 - 1.2 g / L, and the waste phosphoric acid etching solution is diluted with deionized water to a phosphoric acid concentration of 0.5 - 1.2 mol / L; (2) Purification and impurity removal: The lithium-rich leaching solution obtained in step (1) is added with a purification precipitant for purification and impurity removal to obtain metal precipitates containing copper and aluminum and lithium-rich purified solution. The metal precipitates are returned to the copper-aluminum smelting process for further utilization; (3) Double-desalination chamber electrodialysis for quality improvement: The lithium-rich purified solution obtained in step (2) is subjected to bipolar membrane electrodialysis for quality improvement to obtain regenerated LiOH, regenerated phosphoric acid, and lean solution. The regenerated LiOH enters the step (4) of the mixed batching and recycling regeneration process. The regenerated phosphoric acid is used in the etching process of TFT-LCD production in the optoelectronic industry, and the lean solution is returned to the step (1) of the enhanced leaching process for further utilization; (4) Mixed batching and recycling regeneration: The FePO4 / graphite powder obtained in step (1) is mixed with the LiOH obtained in step (3) for mixed batching and recycling regeneration to prepare LiFePO4 / C.

2. The method according to claim 1, wherein The specific steps of ball-milling the black powder obtained by crushing and separating the retired LiFePO4 power battery described in step (1) are as follows: The black powder obtained by disassembling, crushing, separating, or heat-treating and crushing and separating the retired LiFePO4 power battery is ball-milled to a particle size of 180 - 200 mesh.

3. The method according to claim 1, wherein The strengthening agent described in step (1) includes at least one of H2O2 and active oxygen.

4. The method according to claim 1, wherein The purification precipitant described in step (2) is the regenerated LiOH generated in step (3), which is used to adjust the pH of the lithium-rich purified solution to 4.8 - 5.

2.

5. The method according to claim 1, characterized in that, During the double-desalination chamber electrodialysis for quality improvement described in step (3), the bipolar membrane electrodialysis equipment used adopts a double-desalination chamber structure design. Among them, the anode plate and the bipolar membrane form the anode chamber, the cathode plate and the bipolar membrane form the cathode chamber, the bipolar membrane and the cation exchange membrane form the alkali chamber, the cation exchange membrane and the anion exchange membrane form the desalination chamber, and the bipolar membrane and the anion exchange membrane form the acid chamber. Before work, the desalination chamber pumps in the lithium-rich purified solution, the acid chamber pumps in the H3PO4 solution as the initial acid solution, the alkali chamber pumps in the LiOH solution as the initial alkali solution, and the anode chamber and the cathode chamber both pump in the LiH2PO4 solution as the electrode solution. Direct current is passed through the anode plate and the cathode plate to start working. During the working process, the solutions in the double-desalination chamber, the double-alkali chamber, the double-acid chamber, and the anode chamber and the cathode chamber all circulate through the circulation pump until the reaction ends.

6. The method according to claim 5, wherein The cation exchange membrane is at least one of the univalent selective cation exchange membrane Aciplex A-192 and CMS, and the anion exchange membrane uses AMX. The concentration of the electrode solution LiH2PO4 solution is 1.0 to 1.5 mol / L, the concentration of the initial acid solution H3PO4 solution is 0.01 to 0.03 mol / L, and the concentration of the initial alkali solution LiOH solution is 0.03 to 0.09 mol / L.

7. The method according to claim 1, wherein During the mixed ingredient recycling process described in step (4), FePO4 / graphite powder and recycled LiOH are mixed at a molar ratio of Fe to Li of 1:1 to 1:5, and thermally reduced for 1.5 to 3.5 h under a carbon dioxide protection atmosphere at a thermal reduction temperature of 500°C to 950°C to obtain LiFePO4 / C.

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