Treatment method of lithium iron phosphate battery positive electrode material recovery lixivium

Abstract

The invention discloses a treatment method of a lithium iron phosphate battery positive electrode material recovery leachate, and relates to the technical field of battery recovery. The treatment method of the lithium iron phosphate battery positive electrode material recovery leachate comprises the following steps: adjusting the pH value of the leachate to a first pH value, adding a displacer into the leachate, reacting, and filtering to obtain a copper-removed leachate. And continuously adding a displacer into the copper-removed leaching solution until the pH value of the copper-removed leaching solution reaches a second pH value, and filtering after reaction to obtain a primary aluminum-removed leaching solution. An extracting agent is added into the first-stage aluminum-removed leaching solution, and after extraction, a water phase is separated to obtain a second-stage aluminum-removed leaching solution. According to the method provided by the invention, the removal rate of copper and aluminum impurities is relatively high, few types of chemical substances are added in the impurity removal process, the purity of the recycled iron and lithium elements can be increased, and the impurity removal cost can be saved.

Description

Technical Field

[0001] The present application relates to the technical field of battery recycling, and in particular to a method for treating a leaching solution recovered from a positive electrode material of a lithium iron phosphate battery. Background Art

[0002] Lithium iron phosphate materials are environmentally friendly, have abundant raw material sources and low prices, high specific capacity, and excellent cycle performance and thermal stability. Therefore, they are usually used as positive electrode materials for lithium-ion batteries. For used lithium-ion batteries, recycling the lithium iron phosphate materials in the batteries can not only reduce the pollution of waste lithium-ion batteries to the environment, but also bring certain economic benefits.

[0003] In the related art, a method for recycling waste lithium iron phosphate batteries is as follows: after the waste lithium iron phosphate batteries are discharged, disassembled and crushed, the positive electrode sheet fragments are incinerated at high temperature to remove the organic binder, so that the positive electrode active material is separated from the aluminum foil, and the positive electrode active powder is obtained after separation. Then, sulfuric acid is used to dissolve the positive electrode active powder to obtain a leachate, and the leachate is removed and sorted to obtain iron salt, lithium salt, etc., respectively, to complete the recovery of elements such as iron and lithium.

[0004] However, in the above method, the positive electrode active powder obtained from the positive electrode sheet scraps is usually inevitably mixed with impurities such as copper and aluminum. In the traditional impurity removal process, the removal rate of copper and aluminum impurities is low, which seriously affects the purity of the recovered iron and lithium elements. In addition, many types of chemical reagents are used in the process of removing copper and aluminum impurities, resulting in increased impurity removal costs and the introduction of new impurities. Summary of the invention

[0005] The present application provides a method for treating a leaching solution recovered from a positive electrode material of a lithium iron phosphate battery, which has a high removal rate for copper and aluminum impurities and requires fewer types of chemical substances to be added during the impurity removal process, thereby increasing the purity of the recovered iron and lithium elements and saving impurity removal costs.

[0006] The present application provides a method for treating a leaching solution of a lithium iron phosphate battery positive electrode material recovery, the method comprising:

[0007] The pH value of the leaching solution is adjusted to a first pH value, a replacement agent is added to the leaching solution, and the leaching solution is filtered after the reaction to obtain a copper-removing leaching solution.

[0008] Continue to add the replacement agent to the copper removal leachate until the pH value of the copper removal leachate reaches the second pH value, and filter after the reaction to obtain a primary aluminum removal leachate.

[0009] An extractant is added to the primary aluminum removal leaching solution, and after extraction, the water phase is separated to obtain a secondary aluminum removal leaching solution.

[0010] In the above method, by adding a replacement agent to the leachate, copper can be obtained by replacement reaction, and then the copper is removed by filtering to obtain a copper removal leachate. By continuing to add a replacement agent to the copper removal leachate, the pH of the copper removal leachate can be adjusted, and the effect of aluminum removal can be achieved. In the above two steps, the substances added are all the same replacement agent, and the only difference is the pH during the reaction. The purpose of copper removal and aluminum removal can be achieved. Therefore, in the above copper removal and aluminum removal process, less impurities are introduced or no impurities need to be introduced, and the operation is simpler and the cost of impurity removal is lower. In order to further reduce the residual amount of aluminum in the first-level aluminum removal leachate, an extractant is added to the first-level aluminum removal leachate, and the extractant can extract aluminum in a targeted manner, thereby further reducing the aluminum remaining after the replacement agent is added in the above steps for chemical reaction, achieving further removal of aluminum impurities, and finally obtaining a second-level aluminum removal leachate. The impurity copper and impurity aluminum in the second-level aluminum removal leachate are almost completely removed, which can improve the purity of the iron and lithium elements recovered later.

[0011] In one possible design, the displacer is iron powder.

[0012] The principle of adding iron powder to the leachate and filtering after the reaction to obtain the copper removal leachate is that iron can undergo a replacement reaction with copper ions to replace copper ions, thereby achieving the purpose of copper removal without introducing new impurities. The principle of continuing to add the replacement agent to the copper removal leachate until the pH value of the copper removal leachate reaches the second pH value and filtering after the reaction to obtain the primary aluminum removal leachate is that Ksp (AlPO 4 )=9.84×10 -21 、Ksp(FePO 4 ·2H 2 O)=9.91×10 -16 , AlPO 4 Before FePO 4 ·2H 2 O precipitation. The substitution reaction between iron powder and hydrogen ions in the copper removal leachate is used to consume hydrogen ions in the copper removal leachate, thereby increasing the pH of the copper removal leachate and removing aluminum ion impurities in the form of AlPO 4 At the same time, in the above-mentioned steps of removing copper and aluminum by using a replacement agent, iron powder can also reduce Fe 3+ , prevent the formation of iron phosphate precipitation and the loss of iron, thereby improving the iron recovery rate.

[0013] In a possible design, the first pH is 0.6-1.5; when the replacement agent is added to the leachate, the ratio of the sum of the molar amounts of copper ions and iron ions in the leachate to the molar amount of the added iron powder is controlled to be 1:(1.2-1.4).

[0014] Through the above scheme, in the first pH range of 0.6-1.5, the iron powder can more efficiently undergo a replacement reaction with the copper ions, accelerating the reaction efficiency while improving the completeness of the reaction. The molar amount of the added iron powder is slightly greater than the sum of the molar amounts of the copper ions and the iron ions in the leachate, thereby ensuring that the iron powder can relatively completely replace the copper ions and reducing the waste caused by excessive input of iron powder.

[0015] In one possible design, the second pH is 3-4.

[0016] Through the above scheme, the second pH is in the range of 3-4, indicating that the replacement reaction between iron powder and hydrogen ions has reached a certain level, and more phosphate can be released, so that it can combine with aluminum ions to form AlPO 4 Precipitation, that is, within this pH range, AlPO can be generated more efficiently 4 Precipitation, quickly remove aluminum ion impurities in copper leaching solution.

[0017] In a possible design, the replacing agent is continuously added to the copper removal leachate until the pH value of the copper removal leachate reaches a second pH value under the protection of an inert gas.

[0018] Through the above scheme, under the protection of inert gas, it is possible to avoid the Fe 2+ It reacts with oxygen to generate Fe 3+ , prevent the formation of iron phosphate precipitation and the loss of iron, thereby improving the iron recovery rate.

[0019] In a possible design, the extractant includes one of 2-ethylhexyl mono-2-ethylhexyl phosphate, 2-(2-ethylhexyl) phosphate and bis(2,4,4-trimethylpentyl)phosphonic acid.

[0020] Through the above scheme, the above extractant has a high extraction rate for aluminum ions, can effectively remove the aluminum ions in the leachate, and achieve the purpose of impurity removal.

[0021] In one possible design, when the extractant is added to the primary aluminum removal leachate, the volume ratio of the extractant to the primary aluminum removal leachate is 1:(1-2); and / or, the step of adding the extractant to the primary aluminum removal leachate is carried out under the protection of an inert gas.

[0022] Through the above scheme, the volume ratio of the extractant to the primary aluminum removal leaching solution is 1: (1-2). Under this ratio, the extractant has a better extraction effect and improves the completeness of the extractant in extracting aluminum ions. 3+ with Fe 3+ Fe will be extracted preferentially 3+Therefore, the step of adding the extractant to the primary aluminum removal leachate is carried out under the protection of inert gas, which can reduce the Fe 2+ Oxidized to Fe in contact with air 3+ , thereby preventing the extractant from extracting Fe 3+ , causing the loss of iron and increasing the iron recovery rate.

[0023] In a possible design, the treatment method for recovering the leachate of the positive electrode material of the lithium iron phosphate battery also includes: adding a precipitant to the secondary aluminum removal leachate, the precipitant can react with the fluoride ions in the secondary aluminum removal leachate to generate a fluorine-containing precipitate, and filtering after the reaction to obtain a primary fluoride removal leachate.

[0024] Through the above scheme, fluoride ions are separated from the liquid substance by generating fluorine-containing precipitates, and then the purpose of fluorine removal is achieved by filtering, thereby reducing the residual impurity fluoride ions.

[0025] In one possible design, the precipitant is calcium oxide (CaO).

[0026] When the precipitant is added to the secondary aluminum removal leaching solution, the ratio of the molar amount of CaO to the fluoride ion in the secondary aluminum removal leaching solution is 1:(1.5-2).

[0027] Through the above scheme, CaO can combine with fluoride ions in the secondary aluminum removal leachate to form CaF 2 The precipitation is beneficial to the removal of fluoride ions, and CaO is a low-cost material, which can achieve the effect of low-cost fluoride removal. According to the above chemical reaction results, it can be seen that theoretically, the amount of CaO added is 2+ With F - The molar ratio of Ca should be 1:2, so that the reaction can be completely completed. However, in actual implementation, it is often difficult to make Ca 2+ With F - The complete reaction therefore requires the addition of Ca 2+ The input ratio of CaO and the fluoride ion molar amount of the secondary aluminum removal leachate is 1: (1.5-2), which can increase the Ca 2+ The input ratio of Ca 2+ With F - reaction rate, while not causing Ca 2+ Too much input will cause waste, and it can prevent too much CaO input from forming CaF on the surface of CaO powder. 2 , leading to Ca 2+ The problem of inability to dissolve continuously affects the removal of fluoride ions.

[0028] In a possible design, the treatment method for recovering the leachate of the positive electrode material of the lithium iron phosphate battery also includes: passing the primary defluorination leachate into an ion exchange column to defluorinate again to obtain a decontaminated leachate, and the ion exchange column is filled with a defluorination exchange resin.

[0029] Through the above scheme, the ion exchange column can adsorb fluoride ions and further remove the fluoride ions that have not been removed in the previous steps, so that the removal of fluoride ions is more thorough. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 A flow chart of a method for recovering leachate from positive electrode materials of lithium iron phosphate batteries provided in this application.

[0032] Figure 2 A flow chart of another method for processing leachate recovery of lithium iron phosphate battery positive electrode materials provided in this application.

[0033] Figure 3 A flow chart of another method for processing the leachate of lithium iron phosphate battery positive electrode material recovery provided in the present application. DETAILED DESCRIPTION

[0034] In order to make the invention purpose, technical scheme and beneficial technical effect of the present invention clearer, the present invention is further described in detail below in conjunction with examples and comparative examples. It should be understood that the embodiments described in this specification are only for explaining the present invention, not for limiting the present invention, and the formulas, proportions, etc. of the embodiments can be selected according to local conditions without substantial effect on the results.

[0035] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used in the specification of the application are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification, claims and drawings of this application are intended to cover non-exclusive inclusions.

[0036] In the description of the present application, unless otherwise specified, "plurality" means more than two (including two), and similarly, "multiple groups" means more than two groups (including two).

[0037] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase "embodiments" in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0038] For simplicity, only some numerical ranges are explicitly disclosed herein. However, any lower limit can be combined with any upper limit to form an unambiguous range; and any lower limit can be combined with other lower limits to form an unambiguous range, and similarly, any upper limit can be combined with any other upper limit to form an unambiguous range. In addition, although not explicitly stated, each point or single value between the range endpoints is included in the range. Thus, each point or single value can be combined with any other point or single value as its own lower limit or upper limit or with other lower limits or upper limits to form an unambiguous range.

[0039] The above summary of the invention of the present invention is not intended to describe each disclosed embodiment or each implementation in the present invention. The following description more specifically illustrates exemplary embodiments. In many places throughout the application, guidance is provided by a series of examples, which can be used in various combinations. In each example and, enumeration is only as a representative group and should not be interpreted as exhaustive.

[0040] When recycling lithium iron phosphate batteries, the most important thing is to recycle the iron and lithium in the positive active powder. However, in addition to the various additives originally in the positive active powder, the most common impurities come from aluminum impurities caused by the crushing of the positive foil and copper impurities caused by the crushing of the negative foil. In order to improve the purity of the recovered iron and lithium, copper and aluminum impurities need to be removed. In the traditional impurity removal process, the removal rate of copper and aluminum impurities is low, and many types of chemical reagents are used in the process of removing copper and aluminum impurities, which increases the cost of impurity removal and introduces new impurities.

[0041] In view of this, the present application provides a method for treating the leachate of lithium iron phosphate battery positive electrode material recovery, which has a high removal rate for copper and aluminum impurities and uses fewer types of chemical substances during the impurity removal process, thereby increasing the purity of the recovered iron and lithium elements and saving impurity removal costs.

[0042] Figure 1 A flow chart of a method for recovering leaching solution of a positive electrode material of a lithium iron phosphate battery provided in this application, such as Figure 1 As shown, the method includes:

[0043] S100, adjusting the pH value of the leaching solution to a first pH value, adding a replacement agent to the leaching solution, and filtering after the reaction to obtain a copper-removing leaching solution.

[0044] S200, continue to add the replacement agent to the copper removal leachate until the pH value of the copper removal leachate reaches a second pH value, and filter after the reaction to obtain a primary aluminum removal leachate.

[0045] S300, adding an extractant to the primary aluminum removal leachate, and separating the aqueous phase after extraction to obtain a secondary aluminum removal leachate.

[0046] In S100, a replacement agent is added to the leaching solution to obtain copper element through a replacement reaction, and then the copper element is removed by filtering to obtain a copper-removed leaching solution.

[0047] In S200, by continuously adding the displacing agent to the copper removal leaching solution, the pH value of the copper removal leaching solution can be adjusted, so that the displacing agent reacts with aluminum ions and achieves the effect of aluminum removal.

[0048] Among them, in the above-mentioned two steps S100 and S200, the added substances are all the same kind of replacement agents, and the only difference is the pH value during the reaction, thereby being able to achieve the purpose of removing copper and aluminum respectively. Therefore, in the above-mentioned copper removal and aluminum removal processes, less impurities are introduced or no impurities need to be introduced, and the operation is simpler and the cost is lower.

[0049] In order to further reduce the residual aluminum in the primary aluminum removal leachate, in S300, an extractant is added to the primary aluminum removal leachate, and the extractant can extract aluminum in a targeted manner, thereby further reducing the residual aluminum after the chemical reaction of the replacement agent added in the previous step, thereby achieving further removal of aluminum impurities.

[0050] This step uses extraction to remove aluminum. After the extractant extracts the target component, it will be separated from other components, and finally the aqueous phase will be separated to obtain a secondary aluminum removal leachate. Therefore, the extraction process will not introduce excess impurities. The impure copper and impure aluminum in the secondary aluminum removal leachate are almost completely removed, which can improve the purity of the subsequently recovered iron and lithium elements.

[0051] In one possible design, the displacer is iron powder.

[0052] It is understandable that the replacement agent can also be in the form of other iron elements, such as iron sheets, iron blocks, etc., but considering the reaction efficiency, iron powder is the most suitable form of various types of iron elements as a replacement agent.

[0053] Iron powder has a strong reducing property and can completely replace the copper ions in the acidic leaching solution with copper powder. The addition of iron powder not only replaces the copper ions but also reduces the Fe 3+ Reduction to Fe 2+In S100, the chemical reaction that occurs when iron powder is added to the leaching solution is:

[0054] Fe+Cu 2+ =Fe 2+ +Cu

[0055] Fe+2Fe 3+ =3Fe 2+

[0056] The reaction of iron powder replacing copper ions is greatly affected by the pH of the solution. In view of this, in some embodiments, the first pH is set to 0.6-1.5, that is, S100 is: adjusting the pH value of the leachate to 0.6-1.5, adding iron powder to the leachate, filtering after the reaction to obtain a copper-removing leachate.

[0057] In the first pH range of 0.6-1.5, iron powder can more efficiently undergo a replacement reaction with copper ions, which accelerates the reaction efficiency and improves the completeness of the copper removal reaction.

[0058] Illustratively, the first pH may be 1.6, 1, 1.3, 1.5, etc.

[0059] Specifically, in S100, the pH value of the leaching solution is adjusted by adding a common acidic solution such as hydrochloric acid, sulfuric acid, phosphoric acid, etc. to the leaching solution.

[0060] In a possible design, in S100, when adding the replacement agent to the leaching solution, the ratio of the sum of the molar amounts of copper ions and iron ions in the leaching solution to the molar amount of the added iron powder is controlled to be 1:(1.2-1.4).

[0061] By making the molar amount of the added iron powder slightly larger than the sum of the molar amounts of the copper ions and the iron ions in the leaching solution, it is ensured that the iron powder can relatively completely replace the copper ions and the waste caused by excessive input of the iron powder can be reduced.

[0062] Optionally, the ratio of the sum of the molar amounts of copper ions and iron ions in the leachate to the molar amount of the added iron powder is 1:1.2.

[0063] Optionally, the reaction time of the replacement reaction in step S100 is 30 min to 100 min, so that the iron powder and the leaching solution have sufficient reaction time.

[0064] Optionally, the reaction temperature of the replacement reaction in step S100 is at least 60° C., which is the same as the temperature of the aging-water immersion process in the traditional battery recycling process, that is, the leachate obtained by the aging-water immersion process can be directly subjected to step S100. The higher reaction temperature is conducive to the full reaction of the iron powder and the leachate, thereby improving the reaction efficiency.

[0065] In S200, the reason why iron powder can remove aluminum is that there is a large amount of phosphoric acid in the copper removal leaching solution, and the phosphate in it can combine with aluminum to form aluminum phosphate AlPO 4 , can also combine with ferrous ions to form ferric phosphate hydrate FePO 4 ·2H 2 O, and Ksp(AlPO 4 )=9.84×10 -21 , Ksp(FePO 4 ·2H 2 O)=9.91×10 -16 , AlPO 4 The solubility product constant is smaller than that of FePO 4 ·2H 2 O solubility product constant, when the pH value of the copper removal leaching solution increases, AlPO 4 Before FePO 4 ·2H 2 O precipitation. The substitution reaction between iron powder and hydrogen ions in the copper removal leachate is used to consume hydrogen ions in the copper removal leachate, thereby increasing the pH of the copper removal leachate and removing aluminum ion impurities in the form of AlPO 4 Removed as a precipitate.

[0066] In S200, iron powder can also reduce Fe 3+ , prevent the formation of iron phosphate precipitation and the loss of iron, thereby improving the iron recovery rate.

[0067] In S200, the chemical reaction that occurs when iron powder is added to the copper removal leaching solution is:

[0068] Fe+2Fe 3+ =3Fe 2+

[0069] Fe+2H + =Fe 2+ +H 2

[0070] In some embodiments, in S200, the second pH is 3-4.

[0071] The second pH is in the range of 3-4, indicating that the replacement reaction between iron powder and hydrogen ions has reached a certain level, which can release more phosphate, so that the phosphate can combine with aluminum ions to form AlPO 4 Precipitation, that is, within this pH range, AlPO can be generated more efficiently 4 Precipitation, quickly remove aluminum ion impurities in copper leaching solution.

[0072] In a possible design, the step of continuing to add the displacing agent to the copper removal leachate until the pH value of the copper removal leachate reaches a second pH value in S200 is performed under the protection of an inert gas.

[0073] The inert gas is selected from nitrogen or argon. Under the protection of the inert gas, Fe in the copper removal leaching solution can be avoided. 2+ It reacts with oxygen to generate Fe3+, preventing the formation of iron phosphate precipitation and the loss of iron, thereby improving the iron recovery rate.

[0074] In a possible design, the extractant used in S300 includes one of 2-ethylhexyl mono-2-ethylhexyl phosphate, 2-(2-ethylhexyl) phosphate and bis(2,4,4-trimethylpentyl)phosphonic acid.

[0075] The extractant containing the above three substances has a high extraction rate for aluminum ions and can effectively remove aluminum ions in the leachate to achieve the purpose of impurity removal.

[0076] In a specific example, the extractant used in S300 is a bis(2,4,4-trimethylpentyl)phosphonic acid extractant, wherein the mass percentage of bis(2,4,4-trimethylpentyl)phosphonic acid is 20% and the mass percentage of the solvent is 80%. Optionally, the solvent is 80% by mass sulfonated kerosene.

[0077] Optionally, in S300, before adding the extractant to the primary aluminum removal leachate, the pH of the primary aluminum removal leachate is adjusted to 2.5-3.0. In this pH range, any of the above extractants has a high extraction rate for aluminum ions and can effectively remove aluminum ions in the leachate.

[0078] In a possible design, S300, when the extractant is added to the primary aluminum removal leaching solution, the volume ratio of the extractant to the primary aluminum removal leaching solution is 1:(1-2). Under this ratio, the extractant has a better extraction effect and improves the completeness of the extractant in extracting aluminum ions.

[0079] In a specific example, the volume ratio of the extractant to the primary aluminum removal leachate is 1:1.

[0080] Since part of the aluminum ions have been removed in step S200, the amount of the extractant used in step S300 does not need to be too much to achieve the effect of relatively thorough removal of aluminum ion impurities.

[0081] Optionally, the step of adding an extractant to the primary aluminum removal leachate in S300 is also performed under the protection of an inert gas. Under the protection of an inert gas, the Fe 2+ Oxidized to Fe in contact with air 3+ , thereby preventing the extractant from extracting Fe 3+, causing the loss of iron and increasing the iron recovery rate.

[0082] By removing aluminum ions in steps through S200 and S300, chemical impurity removal and extraction agent impurity removal can complement each other. While saving costs, the aluminum ion removal rate is also higher. Both of the above aluminum removal methods will not introduce new impurities into the leachate, and are more practical.

[0083] Figure 2 A flow chart of another method for treating a lithium iron phosphate battery positive electrode material recovery leachate provided in an embodiment of the present application, such as Figure 2 As shown, in a possible design, the method for recovering the leachate from the positive electrode material of a lithium iron phosphate battery also includes:

[0084] S400, adding a precipitant to the secondary aluminum removal leachate, wherein the precipitant can react with fluoride ions in the secondary aluminum removal leachate to generate a fluorine-containing precipitate, and filtering after the reaction to obtain a primary fluoride removal leachate.

[0085] Through the above scheme, fluoride ions are separated from the liquid substance by generating fluorine-containing precipitates, and then the purpose of fluorine removal is achieved by filtering, thereby reducing the residual impurity fluoride ions.

[0086] In one possible design, the precipitant in S400 is calcium oxide (CaO).

[0087] CaO can combine with fluoride ions in the secondary aluminum removal leaching solution to generate CaF 2 Precipitation is beneficial to the removal of fluoride ions, and CaO is a low-cost material, which can achieve the effect of low-cost fluoride removal. The specific reaction formula is:

[0088] Ca 2+ +2F - =CaF 2

[0089] According to the above chemical reaction formula, theoretically, the added Ca 2+ With F - The molar ratio of Ca should be 1:2, so that the reaction can be completely completed. However, in actual implementation, it is often difficult to make Ca 2+ With F - The complete reaction therefore requires the addition of Ca 2+ to increase the removal of fluoride ions.

[0090] In some embodiments, when the precipitant is added to the secondary aluminum removal leachate in S400, the ratio of the molar amount of CaO to the molar amount of fluoride ions in the secondary aluminum removal leachate is 1:(1.5-2).

[0091] By setting the molar ratio of CaO to the fluoride ion in the secondary aluminum removal leaching solution to 1:(1.5-2), the Ca 2+ The input ratio of Ca 2+ With F - reaction rate, while not causing Ca 2+ Too much input will cause waste, and it can prevent too much CaO input from forming CaF on the surface of CaO powder. 2 , leading to Ca 2+ The problem of inability to dissolve continuously affects the removal of fluoride ions.

[0092] In a specific example, the ratio of the molar amount of CaO to the fluoride ion in the secondary aluminum removal leachate is 1:1.5.

[0093] Optionally, the reaction temperature of S400 is 20° C. to 40° C., at which temperature, the reaction efficiency of calcium oxide and fluoride ions in the secondary aluminum removal leaching solution is higher.

[0094] Optionally, the reaction time of S400 is 120 min to 360 min, which can allow calcium oxide and fluoride ions to fully react.

[0095] Optionally, after CaO is added to the secondary aluminum removal leachate, stirring can be performed to evenly disperse the calcium oxide in the secondary aluminum removal leachate, which is beneficial for the full contact between the calcium oxide and the fluoride ions and prevents the calcium oxide from agglomerating and causing CaO to form a lump. 2+ The fluoride ions cannot be dissolved continuously, which affects the removal of fluoride ions. The stirring method can be manual or mechanical. For example, in a specific example, when mechanical stirring is used, the stirring speed is 100 rpm / min to 200 rpm / min.

[0096] Figure 3 For another method of treating the positive electrode material of a lithium iron phosphate battery for recovering the leachate provided in the embodiment of the present application, please refer to Figure 3 In a possible design, the method for recovering the leachate from the positive electrode material of a lithium iron phosphate battery also includes:

[0097] S500, the primary defluorination leaching solution is passed into an ion exchange column, which is filled with a defluorination exchange resin to defluorinate again to obtain a de-impurity leaching solution.

[0098] In some embodiments, the defluorination exchange resin is one of a zirconium-based composite resin or an aluminum-based composite resin.

[0099] In some embodiments, the filling amount of the defluorination exchange resin is 200-400 mL.

[0100] In some embodiments, when the primary defluorination leachate is passed into the ion exchange column, the water inlet flow rate of the primary defluorination leachate is controlled at 100-200 mL / min to prevent the fluoride ions from not being adsorbed in time and flowing out.

[0101] In S500, the ion exchange column can adsorb fluoride ions, further removing the fluoride ions that are not removed in the aforementioned step S400, so that the removal of fluoride ions is more thorough.

[0102] It can be seen that by removing fluoride ions in steps through S400 and S500, chemical impurity removal and ion exchange column adsorption impurity removal can achieve the effect of complementing each other, improve the removal rate of fluoride ions, reduce the replacement frequency of the defluorination exchange resin in the ion exchange column, and reduce material costs and operator labor.

[0103] The following two specific embodiments are used to illustrate the Figure 3 The method shown in the figure is used to treat the specific processing steps of recovering the leachate of the positive electrode material of the lithium iron phosphate battery, and the FePO4 prepared by the impurity-removed leachate obtained by using the two specific embodiments 4 Analyze the ingredients of the product.

[0104] Embodiment 1

[0105] This specific embodiment is to comprehensively remove impurities from the recovered leaching solution of waste lithium iron phosphate positive electrode materials. The general steps can be referred to Figure 3 , the specific steps are:

[0106] (1) Leachate from waste lithium iron phosphate cathode materials: 1 kg of leachate from waste lithium iron phosphate cathode materials was placed in a sealed stirred reactor. The element contents in the leachate are shown in Table 1.

[0107] (2) The initial pH of the recovered leaching solution of waste lithium iron phosphate positive electrode material was adjusted to 1.2, 79 g of iron powder was added, and the ratio of the sum of the molar amounts of copper ions and iron ions in the leaching solution to the molar amount of iron powder was controlled to be 1:1.2. The reaction time was 60 min, the reaction temperature was 80° C., and the copper-removing leaching solution was obtained by filtration.

[0108] (3) Under nitrogen protection, continue to add iron powder to the copper removal leachate until the pH value of the copper removal leachate is 3.5, and filter to obtain a primary aluminum removal leachate.

[0109] (4) Under nitrogen protection, the pH of the primary aluminum removal leachate is adjusted to 2.5, and a bis(2,4,4-trimethylpentyl)phosphonic acid extractant is added, wherein the volume ratio of the added bis(2,4,4-trimethylpentyl)phosphonic acid extractant to the primary aluminum removal leachate is 1:1, and the aqueous phase is separated to obtain a secondary aluminum removal leachate.

[0110] (5) The pH of the secondary aluminum removal leachate was adjusted to 3.8, 2.5 g CaO was added, the reaction time was 180 min, the reaction temperature was 40° C., the stirring speed was 200 rpm / min, and the primary fluoride removal leachate was obtained by filtration.

[0111] (6) 300 mL of zirconium-based composite resin was loaded into an ion exchange column, and after washing with water, acid, alkali, and water, the primary defluorination leachate was passed into the ion exchange column. The water inlet flow rate of the primary defluorination leachate was controlled at 150 mL / min, and the final impurity-removing leachate was obtained by effluent.

[0112] (7) Preparation of FePO using the impurity removal mother liquor obtained by the above impurity removal process 4 , the obtained FePO 4 The product composition analysis results are shown in Table 2.

[0113] Embodiment 2

[0114] This specific embodiment is to comprehensively remove impurities from the recovered leaching solution of waste lithium iron phosphate positive electrode materials. The general steps can be referred to Figure 3 , the specific steps are:

[0115] (1) Recovery of leaching solution from waste lithium iron phosphate cathode materials: 1 kg of the recovery of leaching solution from waste lithium iron phosphate cathode materials was placed in a sealed stirred reactor. The element contents in the recovered leaching solution are shown in Table 1.

[0116] (2) The initial pH of the recovered leaching solution of waste lithium iron phosphate positive electrode material was adjusted to 0.8, 79 g of iron powder was added, the reaction time was 60 min, the reaction temperature was 80° C., and the copper-removing leaching solution was obtained by filtration.

[0117] (3) Under the protection of argon, continue to add iron powder to the copper removal leachate until the pH value of the copper removal leachate is 3.0, and filter to obtain a primary aluminum removal leachate.

[0118] (4) Under argon protection, the pH of the primary aluminum removal leachate is adjusted to 3.0, and a di-(2-ethylhexyl) phosphate extractant is added, wherein the volume ratio of the added di-(2-ethylhexyl) phosphate extractant to the primary aluminum removal leachate is 1:1, and the aqueous phase is separated to obtain a secondary aluminum removal leachate.

[0119] (5) The pH of the secondary aluminum removal leachate was adjusted to 4.3, 2.5 g CaO was added, the reaction time was 180 min, the reaction temperature was 40° C., the stirring speed was 200 rpm / min, and the primary fluoride removal leachate was obtained by filtration.

[0120] (6) 300 mL of zirconium-based composite resin is loaded into an ion exchange column, and after water washing, acid washing, alkali washing, and water washing, the primary defluorination leachate is passed into the ion exchange column. The water inlet flow rate of the primary defluorination leachate should be controlled at 150 mL / min, and the final impurity-removing leachate is obtained from the effluent.

[0121] (7) Preparation of FePO using the impurity removal mother liquor obtained by the above impurity removal process 4 , the obtained FePO 4 The product composition analysis results are shown in Table 2.

[0122] Table 1

[0123]

[0124] Table 2

[0125]

[0126] By comparing Table 1 and Table 2, we can see that:

[0127] Before impurity removal, Cu 2+ The content of Cu is 2.5% of the mass of the leaching solution. After comprehensive impurity removal using the steps of Example 1, the content of Cu is only 1.5% of FePO 4 The content of Cu is only 0.0003% of FePO4, which is much smaller than the 0.005% required by the industry standard and the 0.0015% required by the enterprise standard. After comprehensive impurity removal using the steps of Example 2, the content of Cu is only 0.0003% of FePO4. 4 The quality of 0.0004% is far less than the 0.005% required by the industry standard and also less than the 0.0015% required by the enterprise standard.

[0128] Before impurity removal, Al 3+ The content of Al accounts for 1.47% of the mass of the leaching solution. After comprehensive impurity removal using the steps of Example 1, the content of Al only accounts for 1.47% of the mass of FePO 4 The content of Al is only 0.0015% of FePO4, which is much lower than the 0.005% required by the enterprise standard. After comprehensive impurity removal using the steps of Example 2, the content of Al is only 0.0015% of FePO4. 4 The quality is 0.002%, which is far less than the 0.005% required by the enterprise standard.

[0129] Before impurity removal, F - The content of F accounts for 0.13% of the mass of the leaching solution. After comprehensive impurity removal using the steps of Example 1, the content of F only accounts for 0.13% of the mass of FePO 4 The content of F in FePO is only 0.0007% of the total mass, which is much lower than the 0.005% required by the enterprise standard. After comprehensive impurity removal using the steps of Example 2, the content of F only accounts for 0.0007% of the total mass of FePO. 4 The quality is 0.0011%, which is far less than the 0.005% required by the enterprise standard.

[0130] In addition, it can be seen from Table 2 that no matter whether the steps of Example 1 or Example 2 are used for comprehensive impurity removal, the FePO prepared by the impurity removal leaching solution is 4 The mass fractions of all other impurities except the above-mentioned copper, aluminum and fluorine are far lower than the industry standards and enterprise standards, and can meet the requirements for recycling.

[0131] It can be seen that the treatment method for recovering the leachate of the lithium iron phosphate battery positive electrode material provided in the present application has a high removal rate for copper, aluminum and fluorine impurities, and the impurities introduced during the removal process are also relatively small.

Claims

1. A method for recovering leaching solution of positive electrode material of lithium iron phosphate battery, characterized in that: include: The pH value of the leachate is adjusted to a first pH value, a replacement agent is added to the leachate, and after reaction, the leachate is filtered to obtain a copper-removing leachate; Continue to add the replacement agent to the copper removal leachate until the pH value of the copper removal leachate reaches a second pH value, and filter after the reaction to obtain a primary aluminum removal leachate; An extractant is added to the primary aluminum removal leachate, and after extraction, the aqueous phase is separated to obtain a secondary aluminum removal leachate.

2. The method for recovering leaching solution of lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: The displacing agent is iron powder.

3. The method for recovering leaching solution of lithium iron phosphate battery positive electrode material according to claim 2, characterized in that: The first pH is 0.6-1.5; When the replacement agent is added to the leaching solution, the ratio of the sum of the molar amounts of copper ions and iron ions in the leaching solution to the molar amount of the added iron powder is controlled to be 1:(1.2-1.4).

4. The method for recovering leaching solution of lithium iron phosphate battery positive electrode material according to claim 2, characterized in that: The second pH is 3-4.

5. The method for recovering leaching solution of lithium iron phosphate battery positive electrode material according to claim 2, characterized in that: The replacing agent is continuously added to the copper removal leachate until the pH value of the copper removal leachate reaches a second pH value under the protection of an inert gas.

6. The method for recovering leaching solution of lithium iron phosphate battery cathode material according to claim 1, characterized in that: The extractant comprises one of 2-ethylhexyl phosphate mono-2-ethylhexyl ester, 2-(2-ethylhexyl) phosphate and bis(2,4,4-trimethylpentyl)phosphonic acid.

7. The method for recovering leaching solution of lithium iron phosphate battery positive electrode material according to claim 6, characterized in that: When adding the extractant to the primary aluminum removal leachate, the volume ratio of the extractant to the primary aluminum removal leachate is 1:(1-2); and / or The step of adding an extractant to the primary aluminum removal leachate is carried out under the protection of an inert gas.

8. The method for recovering leaching solution of lithium iron phosphate battery positive electrode material according to claim 1, characterized in that: The method further comprises: adding a precipitant to the secondary aluminum removal leachate, wherein the precipitant can react with fluoride ions in the secondary aluminum removal leachate to generate fluorine-containing precipitates, and filtering after the reaction to obtain a primary fluoride removal leachate.

9. The method for recovering leaching solution of lithium iron phosphate battery positive electrode material according to claim 8, characterized in that: The precipitant is calcium oxide (CaO); When the precipitant is added to the secondary aluminum removal leaching solution, the ratio of the molar amount of CaO to the fluoride ion in the secondary aluminum removal leaching solution is 1:(1.5-2).

10. The method for recovering leaching solution of lithium iron phosphate battery positive electrode material according to claim 8, characterized in that: The method further comprises: passing the primary defluorination leaching solution into an ion exchange column to defluorinate again to obtain a de-impurity leaching solution, wherein the ion exchange column is filled with a defluorination exchange resin.

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