Recycling method of lithium manganese iron phosphate waste

Abstract

The invention provides a method for recycling lithium manganese iron phosphate waste. The recovery method comprises the following steps: (1) mixing the lithium manganese iron phosphate waste with a first acid solution, introducing sulfur dioxide and oxygen, and carrying out oxidation leaching to obtain leached slurry; (2) the leaching slurry is subjected to copper removal treatment, and leaching residues and leaching liquid are obtained; (3) mixing the leaching residues obtained in the step (2) with a second acid solution, adjusting the pH value, and carrying out a first precipitation reaction to obtain ferromanganese phosphate; and carrying out lithium extraction treatment on the leachate obtained in the step (2) to obtain purified lithium salt. According to the recovery method provided by the invention, the oxidation effect is better, a large number of cation impurities are not introduced, all-component recovery of the lithium iron manganese phosphate battery positive electrode material can be realized, and a battery-grade purified lithium salt material and a precursor iron manganese phosphate product required by the battery-grade lithium iron manganese phosphate positive electrode material can be obtained; and the process cost is low, the added value of the product is improved, and the actual production requirement is better met.

Description

Technical Field

[0001] The invention belongs to the technical field of battery recycling and relates to a method for recycling lithium iron manganese phosphate waste. Background Art

[0002] Lithium iron phosphate lithium-ion battery is the preferred power source for new energy vehicles. Lithium iron phosphate battery has the advantages of high cycle performance and high safety performance. The recycling of lithium iron phosphate batteries has a mature process. Lithium iron manganese phosphate, a lithium-ion battery similar to lithium iron phosphate, is expected to become a new generation of high energy density power battery positive electrode material due to its high energy density, higher safety performance and relatively low price. In order to realize the recycling of lithium iron manganese phosphate, the recycling of lithium iron manganese phosphate waste has become a research hotspot.

[0003] At present, the recovery of lithium manganese iron phosphate mainly involves wet selective recovery of lithium elements, impurity removal, and distributed precipitation to obtain iron phosphate, manganese phosphate or ferromanganese phosphate and other precipitates.

[0004] For example, CN115632185A discloses a method for recycling and treating the positive electrode material of waste lithium iron manganese phosphate batteries with all components, which comprises preparing a lithium leaching solution and a manganese iron phosphorus leaching solution for successively leaching the corresponding lithium and phosphorus in the positive electrode powder of the waste lithium iron manganese phosphate batteries to obtain a lithium leaching solution and a manganese iron phosphorus-containing solution; purifying and refining the leached lithium leaching solution to obtain high-purity lithium carbonate; reducing the iron ions in the manganese iron phosphorus-containing solution after leaching to divalent iron ions, neutralizing with alkali, and filtering to obtain crude manganese iron phosphate; adding phosphoric acid solution to dissolve the crude manganese iron phosphate, injecting the dissolved manganese iron phosphate solution into a reactor at a certain flow rate to prepare a manganese iron phosphate precursor, and at the same time, injecting an alkali solution into the reactor at a certain ratio and flow rate, filtering, and drying the filter residue to obtain a manganese iron phosphate precursor. Although the technical solution in this document achieves the recovery of all components of lithium manganese iron phosphate to obtain battery-grade lithium carbonate and manganese iron phosphate precursors, its selective lithium leaching agent is prepared from hydrogen peroxide, acid, and persulfate. The oxidizing property of hydrogen peroxide is not enough to oxidize Mn in the leaching solution. 2+ , persulfate is needed to cooperate with hydrogen peroxide to selectively leach lithium manganese iron phosphate. Using persulfate as a leaching agent introduces more cationic impurities, and persulfate is expensive, which increases the process cost.

[0005] For example, CN108736090A, CN115535987A, CN115448335A, etc. disclose a method for selectively extracting lithium from waste manganese iron phosphate lithium batteries (or their positive electrode waste powder). The above-mentioned documents use strong oxidants such as ammonium persulfate, hydrogen peroxide, ozone, and sodium persulfate to directly selectively oxidize and leach waste manganese iron phosphate lithium batteries (or their positive electrode waste powder). Compared with the above-mentioned method of all-element leaching-precipitation separation and recovery of lithium, it can selectively leach lithium, and the process is relatively simple. However, although the selective leaching effect of lithium in the selective lithium extraction method is very good, because the content of iron and manganese in lithium manganese iron phosphate is high, a large amount of oxidants will be consumed, and these strong oxidants are generally very expensive, and the storage of too much strong oxidants will also bring greater safety risks in production.

[0006] Therefore, how to achieve effective recycling of lithium iron manganese phosphate waste while reducing process costs is a technical problem that needs to be solved urgently. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a method for recycling lithium iron manganese phosphate waste. The recycling method provided by the present invention has better oxidation effect, does not introduce a large amount of cationic impurities, can achieve full component recovery of lithium iron manganese phosphate battery positive electrode materials, and can obtain battery-grade purified lithium salt materials and battery-grade lithium iron manganese phosphate precursor iron manganese phosphate products required for positive electrode materials; and the process cost is low, the added value of the product is increased, and the actual production needs are better met.

[0008] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides a method for recycling lithium iron manganese phosphate waste, the recycling method comprising the following steps:

[0010] (1) mixing the lithium iron manganese phosphate waste with the first acid solution, introducing sulfur dioxide and oxygen to perform oxidation leaching to obtain a leached slurry;

[0011] (2) removing copper from the leached slurry to obtain leached residue and leaching liquid;

[0012] (3) mixing the leached residue of step (2) with the second acid solution, adjusting the pH value to carry out a first precipitation reaction to obtain ferromanganese phosphate; and subjecting the leached solution of step (2) to lithium extraction treatment to obtain purified lithium salt.

[0013] It should be noted that the lithium iron manganese phosphate waste in the present invention is the waste positive electrode waste of waste lithium iron manganese phosphate batteries, and the specific recycling methods are all conventional technical solutions, and the technical solutions that can be known within a reasonable range by technical personnel in this field are all applicable to the present invention.

[0014] Exemplarily, the present invention provides a method for obtaining lithium iron manganese phosphate waste, the method comprising:

[0015] The waste lithium iron manganese phosphate batteries are discharged, disassembled, crushed and screened in sequence to separate the waste lithium iron manganese phosphate powder.

[0016] The recovery method provided by the present invention utilizes the interaction between sulfur dioxide and oxygen in a mixed system of lithium iron phosphate waste and a first acid solution to generate strong oxidizing free radical ions with a high redox potential, which can convert Fe in the lithium iron phosphate waste into 2+ and Mn 2+ The oxidation is carried out with excellent oxidation effect, which not only increases the valence state of manganese in lithium iron manganese phosphate and makes manganese precipitate in the leaching residue, but also realizes the selective extraction of lithium in lithium iron manganese phosphate, avoiding the problem of introducing a large amount of cationic impurities when using strong oxidants such as persulfate; the leaching slurry after oxidation leaching is subjected to deep copper removal treatment to reduce the copper and aluminum impurity content in the obtained leaching residue, thereby obtaining high-purity leaching residue and leachate; the leaching residue is then mixed with the second acid solution, and the pH value is adjusted to carry out the first precipitation reaction, so as to obtain the precursor manganese phosphate product required for the battery-grade lithium iron manganese phosphate positive electrode material; and after the leaching solution is subjected to lithium extraction treatment, a battery-grade purified lithium salt material can be obtained.

[0017] In the present invention, sulfur dioxide and oxygen react in a mixed system of lithium iron manganese phosphate waste and a first acid solution to generate strong oxidizing free radical ions, so that divalent iron and divalent manganese in the solution are oxidized, wherein the strong oxidizing free radical ions can be used as an oxidant for selective oxidation leaching and lithium extraction; however, if sulfur dioxide and oxygen are introduced into a non-solution system at a high temperature (700-900° C.) for solid-phase lithium extraction, strong oxidizing free radical ions cannot be obtained.

[0018] In the present invention, after sulfur dioxide and oxygen are introduced into the mixed system of lithium iron manganese phosphate waste and the first acid solution, the reaction process in the system is as follows:

[0019] SO2 + H2O →H2SO3 (1)

[0020] H2SO3 → HSO3 - +H + (2)

[0021] Fe 2+ + HSO3 - → FeHSO3 + (3)

[0022] 4FeHSO3 + + O2 → 4FeSO3 ++ 2H2O (4)

[0023] FeSO3 + + → Fe 2+ + SO3 .- (5)

[0024] SO3 .- + O2 → SO5 .- (6)

[0025] SO5 .- + HSO3 - → SO4 2- + SO4 .- + H + (7)

[0026] SO5 .- + Mn 2+ + H + → HSO5 - + Mn 3+ (8).

[0027] That is, the present invention simultaneously introduces sulfur dioxide and oxygen into a mixed system of lithium manganese iron phosphate waste and the first acid solution, thereby obtaining sulfite radical ions, peroxysulfate radical ions and highly oxidizing sulfate radical ions, which have a relatively high redox potential and are beneficial to the oxidation of manganese ions and iron ions in the lithium manganese iron phosphate waste, so that manganese and iron are precipitated in the leaching residue, thereby obtaining a lithium-containing leachate with high purity and few impurities.

[0028] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the technical objectives and beneficial effects of the present invention can be better achieved and realized.

[0029] Preferably, the concentration of the first acid solution in step (1) is 1-5 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L.

[0030] Preferably, the molar amount of acid added in the first acid solution in step (1) is 1 to 2 times the theoretical amount added, for example, 1 time, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times or 2 times, etc.

[0031] In the present invention, the specific type of the first acid solution is a conventional technical solution, that is, an acid solution that can be used for acid leaching of lithium manganese iron phosphate, and the present invention is applicable. For example, the acid in the first acid solution includes but is not limited to at least one of sulfuric acid, hydrochloric acid or nitric acid; and it should be noted that the theoretical addition amount of the first acid solution in the present invention refers to the molar amount.

[0032] Specifically:

[0033] When the acid in the first acid solution is sulfuric acid, the theoretical molar amount of sulfuric acid added is 0.5 times the total molar amount of lithium in the mixed system of lithium iron manganese phosphate waste and the first acid solution, that is, n(H2SO4):n(Li)=1:2.

[0034] When the acid in the first acid solution is hydrochloric acid, the theoretical molar amount of hydrochloric acid added is 1 times the total molar amount of lithium in the mixed system of lithium iron manganese phosphate waste and the first acid solution, that is, n(HCl):n(Li)=1:1.

[0035] When the acid in the first acid solution is nitric acid, the theoretical molar amount of nitric acid added is 1 times the total molar amount of lithium in the mixed system of lithium iron manganese phosphate waste and the first acid solution, that is, n(HNO3):n(Li)=1:1.

[0036] Preferably, the flow rate of sulfur dioxide is 20 to 50 L / h, for example, 20 L / h, 25 L / h, 30 L / h, 35 L / h, 40 L / h, 45 L / h or 50 L / h.

[0037] Preferably, the oxygen flow rate is 10 to 30 L / h, for example, 10 L / h, 13 L / h, 15 L / h, 18 L / h, 20 L / h, 23 L / h, 25 L / h, 28 L / h or 30 L / h.

[0038] In the present invention, by adjusting the flow rate of sulfur dioxide to 20-50 L / h and / or the flow rate of oxygen to 10-30 L / h, it is more conducive to forming enough strong oxidizing free radical ions.

[0039] Preferably, the copper removal agent used in the copper removal treatment process in step (2) comprises a compound containing thiomolybdate ions, and the compound containing thiomolybdate ions comprises ammonium tetrathiomolybdate.

[0040] In the present invention, a compound containing thiomolybdate ions is selected as a copper removal agent because the ions can form a complex with the copper ions in the leaching slurry and will not change the morphology of the leached slag, thereby realizing the copper removal treatment of the leached slag; further, ammonium tetrathiomolybdate is selected as a copper removal agent, and the ammonium ions therein can also form a copper-ammonia complex with the copper ions, and the two complexes can remove the copper ions in the leached slag, and the thiomolybdate ions and the ammonium ions cooperate with each other to reduce the copper content in the leached slag, thereby realizing the deep copper removal of the leached slag; however, if a conventional copper removal agent, such as sodium sulfate, iron sulfide, ammonium sulfide or iron powder, is selected, it is often used to remove copper impurities in the leachate, but the deep copper removal treatment of the leached slag in the present invention cannot be realized.

[0041] Preferably, in the copper removal process of step (2), the amount of the copper removal agent used is 1 to 2 times the mass of the copper in the leaching slurry, for example, 1 times, 1.1 times, 1.2 times, 1.3 times, 1.4 times, 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times or 2 times, etc.

[0042] Preferably, the leached residue after the copper removal treatment in step (2) is sequentially subjected to acid washing and water washing.

[0043] In the present invention, the leached residue after the copper removal treatment in step (2) is successively subjected to acid washing and water washing, which can further reduce the aluminum content in the leached residue, thereby obtaining leached residue with higher purity.

[0044] Specifically, the pickling is carried out by dilute acid cleaning, such as 0.1-0.4 mol / L dilute sulfuric acid, 0.1-0.4 mol / L dilute hydrochloric acid, 0.1-0.4 mol / L dilute nitric acid, etc.

[0045] Preferably, the concentration of the second acid solution in step (3) is 1 to 5 mol / L, for example, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L or 5 mol / L.

[0046] Preferably, in step (3), the leached residue in step (2) is mixed with the second acid solution to obtain ferromanganese phosphate liquid and acid-soluble residue.

[0047] In the present invention, the leached residue is first mixed with the second acid solution for acid dissolution, so that the leached residue containing iron phosphate and manganese phosphate in step (2) is dissolved in the second acid solution to obtain manganese phosphate iron liquid, wherein the acid-soluble residue other than iron phosphate and manganese phosphate which is insoluble in the second acid solution will be further removed.

[0048] Further:

[0049] In step (3), the mixing temperature of the leached residue and the second acid solution can be 40-60°C, for example, 40°C, 45°C, 50°C, 55°C or 60°C, and the mixing time can be 1-10h, for example, 1h, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h or 10h, etc.

[0050] The acid in the second acid solution in step (3) includes but is not limited to at least one of sulfuric acid, hydrochloric acid or nitric acid.

[0051] In step (3), the dosage of the second acid solution is 1 to 2 times, for example, 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2 times the total mass of iron and manganese in the leached slag.

[0052] Preferably, the pH value adjusted in step (3) is to adjust the pH value of the ferromanganese phosphate solution.

[0053] Preferably, after adjusting the pH value in step (3), the pH value in the system is maintained at 4 to 5, for example, 4, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 or 5.

[0054] Preferably, the reaction temperature for adjusting the pH value for the first precipitation reaction in step (3) is 30-80°C, for example, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, and the first precipitation reaction time is 5-10h, for example, 5h, 6h, 7h, 8h, 9h or 10h, etc.

[0055] In the present invention, the pH value of the mixed system of the leached residue and the second acid solution can be adjusted by adding a precipitant solution, and the present invention does not specifically limit the material type of the precipitant, and the present invention is applicable to any material type that can adjust the pH value but does not affect the precipitation of the ferromanganese phosphate product; for example, the precipitant can be liquid alkali and / or ammonia water, and the liquid alkali includes sodium hydroxide or potassium hydroxide, etc.

[0056] Preferably, the lithium extraction method in step (3) comprises:

[0057] The leaching solution in step (2) is decontaminated to obtain a lithium-rich solution, and the lithium-rich solution is subjected to a second precipitation reaction to obtain purified lithium salt.

[0058] In the present invention, the leaching solution obtained in step (2) is a lithium-containing leaching solution, which is removed by impurities to obtain a high-purity lithium-rich solution, and the high-purity lithium-rich solution is reacted with a precipitant to obtain a battery-grade lithium salt.

[0059] It should be noted that the present invention does not specifically limit the method for removing impurities from the leachate, and the present invention is applicable to any conventional method for removing impurities from the lithium-containing leachate in the present invention, such as the impurity removal process of adding liquid alkali to adjust the pH value, wherein the liquid alkali includes at least one of sodium hydroxide, magnesium hydroxide or calcium hydroxide.

[0060] Preferably, the pH value of the impurity removal process is 5-6, for example, 5, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9 or 6.

[0061] In the present invention, the type of precipitant substance used in the second precipitation reaction process is selected according to conventional technology, and can be adaptively selected and adjusted according to the type of lithium salt obtained. For example, the precipitant can be sodium carbonate or sodium phosphate; and the amount of precipitant added is also selected according to conventional technology, and the mass amount of precipitant added is also selected according to conventional technology, and its mass amount added is 1.1 to 2 times the theoretical mass amount required to obtain the corresponding lithium salt, that is, excessive addition, which can make the reaction more thorough.

[0062] As a preferred technical solution, the recovery method comprises the following steps:

[0063] (1) mixing the lithium iron manganese phosphate waste with the first acid solution, introducing sulfur dioxide at a flow rate of 20 to 50 L / h and oxygen at a flow rate of 10 to 30 L / h, and performing oxidative leaching to obtain a leached slurry;

[0064] (2) removing copper from the leached slurry using ammonium tetrathiomolybdate to obtain a leached residue and a leached liquid after the copper is removed, and acid-washing and water-washing the leached residue after the copper is removed to obtain a washed leached residue;

[0065] (3) mixing the washed leached residue of step (2) with the second acid solution to obtain ferromanganese phosphate liquid and acid-soluble residue, adjusting the pH value of the ferromanganese phosphate liquid to 4 to 5, maintaining the pH value of the system at 4 to 5 to perform a first precipitation reaction to obtain ferromanganese phosphate;

[0066] The leaching solution in step (2) is decontaminated under a pH value of 5 to 6 to obtain a lithium-rich solution, and the lithium-rich solution is subjected to a second precipitation reaction to obtain purified lithium salt.

[0067] It should be noted that due to space limitations and to avoid redundancy, the present invention does not exhaustively list all point values ​​within the above numerical range, but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0068] Compared with the prior art, the present invention has the following beneficial effects:

[0069] The recovery method provided by the present invention utilizes the action of sulfur dioxide and oxygen in a mixed system of lithium iron manganese phosphate waste and a first acid solution to generate strong oxidizing free radical ions with a high redox potential, which can remove Fe in the lithium iron phosphate waste. 2+ and Mn 2+ The oxidation is carried out with excellent oxidation effect, which not only increases the valence state of manganese in lithium iron manganese phosphate and makes manganese precipitate in the leaching residue, but also realizes the selective extraction of lithium in lithium iron manganese phosphate, avoiding the problem of introducing a large amount of cationic impurities when using strong oxidants such as persulfate; the leaching slurry after oxidation leaching is subjected to deep copper removal treatment to reduce the copper and aluminum impurity content in the obtained leaching residue, thereby obtaining high-purity leaching residue and leachate; the leaching residue is then mixed with the second acid solution, and the pH value is adjusted to carry out the first precipitation reaction, so as to obtain the precursor manganese phosphate product required for the battery-grade lithium iron manganese phosphate positive electrode material; and after the leaching solution is subjected to lithium extraction treatment, a battery-grade purified lithium salt material can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 A schematic flow chart of the method for recovering lithium iron manganese phosphate waste provided in Example 1. DETAILED DESCRIPTION

[0071] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0072] 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 herein 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 this application are intended to cover non-exclusive inclusions.

[0073] In the description of this application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0074] In a specific embodiment, the present invention provides a method for obtaining lithium iron manganese phosphate waste, the method comprising:

[0075] The waste lithium iron manganese phosphate batteries are discharged, disassembled, crushed and screened in sequence to separate the waste lithium iron manganese phosphate powder.

[0076] The following examples and comparative examples all adopt the above-mentioned treatment method to obtain lithium iron phosphate waste powder, and are the same type of batteries.

[0077] Example 1

[0078] This embodiment provides a method for recycling lithium iron manganese phosphate waste, such as Figure 1 As shown, the recycling method is as follows:

[0079] (1) 100 g of lithium manganese iron phosphate waste was mixed with a sulfuric acid solution (first acid solution) having a molar concentration of 1 mol / L to prepare a slurry, wherein the molar amount of sulfuric acid added was 1.5 times the theoretical amount (the theoretical amount was 0.5 times the total molar amount of lithium in the prepared slurry), sulfur dioxide and oxygen were introduced, and oxidative leaching was performed at 50° C. for 4 h, wherein the flow rate of sulfur dioxide was 25 L / h, and the flow rate of oxygen was 15 L / h, to obtain a leached slurry;

[0080] (2) adding ammonium tetrathiomolybdate copper remover to the leached slurry in step (1), wherein the amount of the copper remover is 1 times the mass of copper in the leached slurry, to obtain leached residue and leachate after copper removal, and subjecting the leached residue after copper removal to pickling and water washing with 0.2 mol / L dilute sulfuric acid to obtain leached residue after water washing;

[0081] (3) mixing the washed leached residue of step (2) with a 1.2 mol / L sulfuric acid solution (second acid solution) for acid dissolution treatment, wherein the amount of sulfuric acid solution used is 1.5 times the total mass of iron and manganese in the leached residue, the acid dissolution temperature is 60° C., and the acid dissolution time is 4 h, to obtain ferromanganese phosphate liquid and acid-dissolved residue,

[0082] The obtained ferromanganese phosphate liquid and sodium hydroxide solution were slowly introduced into the reaction kettle, the flow rate of the ferromanganese phosphate liquid was 3 mL / min, the pH of the system was maintained at 4-4.5 as measured by a pH meter, and the first precipitation reaction was carried out at 50° C. for 6 hours to obtain a ferromanganese phosphate product;

[0083] The leachate obtained in step (2) is added with liquid alkali sodium hydroxide to adjust the pH to 6 to obtain a lithium-rich solution after impurities are removed, and a precipitant sodium carbonate is added (the amount of sodium carbonate added is 1.5 times the theoretical mass amount of lithium salt required in the lithium-rich solution) to carry out a second precipitation reaction at 90° C. for 3 hours to obtain lithium salt lithium carbonate.

[0084] Example 2

[0085] This embodiment provides a method for recycling lithium iron manganese phosphate waste, and the recycling method is as follows:

[0086] (1) 100 g of lithium manganese iron phosphate waste was mixed with a nitric acid solution (first acid solution) having a molar concentration of 2 mol / L to prepare a slurry, wherein the molar amount of nitric acid added was 1 times the theoretical amount (the theoretical amount was 1 times the total molar amount of lithium in the prepared slurry), sulfur dioxide and oxygen were introduced, and oxidative leaching was performed at 50° C. for 4 h, wherein the flow rate of sulfur dioxide was 25 L / h, and the flow rate of oxygen was 15 L / h, to obtain a leached slurry;

[0087] (2) adding ammonium tetrathiomolybdate copper remover to the leached slurry in step (1), wherein the amount of the copper remover is 1.5 times the mass of copper in the leached slurry, to obtain leached residue and leachate after copper removal, and subjecting the leached residue after copper removal to pickling and water washing with 0.4 mol / L dilute nitric acid to obtain leached residue after water washing;

[0088] (3) mixing the washed leached residue of step (2) with a 1.2 mol / L sulfuric acid solution (second acid solution) for acid dissolution treatment, wherein the amount of the sulfuric acid solution is 1 times the total mass of iron and manganese in the leached residue, the acid dissolution temperature is 60° C., and the acid dissolution time is 4 h, to obtain ferromanganese phosphate liquid and acid-dissolved residue,

[0089] The obtained ferromanganese phosphate liquid and sodium hydroxide solution were slowly introduced into the reaction kettle, the flow rate of the ferromanganese phosphate liquid was 3 mL / min, the pH of the system was maintained at 4-4.5 as measured by a pH meter, and the reaction was carried out at 50° C. for 6 hours to obtain a ferromanganese phosphate product;

[0090] Liquid sodium hydroxide is added to the leachate obtained in step (2) to adjust the pH to 6 to obtain a lithium-rich solution after impurities are removed, and a precipitant sodium phosphate dodecahydrate is added (the amount of sodium phosphate dodecahydrate added is 1.1 times the theoretical mass amount of lithium salt required in the lithium-rich solution) to carry out precipitation reaction at 90° C. for 3 hours to obtain lithium salt lithium phosphate.

[0091] Example 3

[0092] This embodiment provides a method for recycling lithium iron manganese phosphate waste, and the recycling method is as follows:

[0093] (1) 1000 g of lithium manganese iron phosphate waste was mixed with a sulfuric acid solution (first acid solution) having a molar concentration of 2 mol / L to prepare a slurry, wherein the molar amount of sulfuric acid added was twice the theoretical amount (the theoretical amount was 0.5 times the total molar amount of lithium in the prepared slurry), sulfur dioxide and oxygen were introduced, and oxidative leaching was performed at 50° C. for 4 h, wherein the flow rate of sulfur dioxide was 25 L / h, and the flow rate of oxygen was 15 L / h, to obtain a leached slurry;

[0094] (2) adding ammonium tetrathiomolybdate copper remover to the leached slurry in step (1), wherein the amount of the copper remover is 1 times the mass of copper in the leached slurry, to obtain leached residue and leachate after copper removal, and subjecting the leached residue after copper removal to pickling and water washing with 0.2 mol / L dilute sulfuric acid to obtain leached residue after water washing;

[0095] (3) mixing the washed leached residue of step (2) with a 1.2 mol / L sulfuric acid solution (second acid solution) for acid dissolution treatment, wherein the amount of sulfuric acid solution used is twice the total mass of iron and manganese in the leached residue, the acid dissolution temperature is 60° C., and the acid dissolution time is 4 h, to obtain ferromanganese phosphate liquid and acid-dissolved residue,

[0096] The obtained ferromanganese phosphate liquid and sodium hydroxide solution were slowly introduced into the reaction kettle, the flow rate of the ferromanganese phosphate liquid was 3 mL / min, the pH of the system was maintained at 4-4.5 as measured by a pH meter, and the first precipitation reaction was carried out at 50° C. for 6 hours to obtain a ferromanganese phosphate product;

[0097] The leachate obtained in step (2) is added with liquid alkali sodium hydroxide to adjust the pH to 6 to obtain a lithium-rich solution after impurities are removed, and a precipitant sodium carbonate is added (the amount of sodium carbonate added is twice the theoretical mass amount required for the lithium salt in the lithium-rich solution) to carry out a second precipitation reaction at 90° C. for 3 hours to obtain lithium salt lithium carbonate.

[0098] Example 4

[0099] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the flow rate of sulfur dioxide is 20 L / h, and the flow rate of oxygen is 10 L / min.

[0100] The remaining recovery methods and parameters were the same as those in Example 1.

[0101] Example 5

[0102] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the flow rate of sulfur dioxide is 50 L / h, and the flow rate of oxygen is 30 L / min.

[0103] The remaining recovery methods and parameters were the same as those in Example 1.

[0104] Example 6

[0105] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the flow rate of sulfur dioxide is 15 L / h.

[0106] The remaining recovery methods and parameters were the same as those in Example 1.

[0107] Example 7

[0108] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the flow rate of sulfur dioxide is 55 L / h.

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

[0110] Example 8

[0111] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the oxygen flow rate is 5 L / min.

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

[0113] Example 9

[0114] The difference between this embodiment and embodiment 1 is that in step (1) of this embodiment, the oxygen flow rate is 35 L / min.

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

[0116] Comparative Example 1

[0117] (1) 100 g of lithium manganese iron phosphate waste is mixed with a sulfuric acid solution (first acid solution) having a molar concentration of 1 mol / L to prepare a slurry, wherein the molar amount of sulfuric acid added is 1.5 times the theoretical amount (the theoretical amount is 0.5 times the total molar amount of lithium in the prepared slurry), and then hydrogen peroxide is pumped in as an oxidant to obtain a leaching slurry;

[0118] (2) adding ammonium tetrathiomolybdate copper remover to the leached slurry in step (1), wherein the amount of the copper remover is 1 times the mass of copper in the leached slurry, to obtain leached residue and leachate after copper removal, and subjecting the leached residue after copper removal to pickling and water washing with 0.2 mol / L dilute sulfuric acid to obtain leached residue after water washing;

[0119] (3) mixing the washed leached residue of step (2) with a 1.2 mol / L sulfuric acid solution (second acid solution) for acid dissolution treatment, wherein the amount of sulfuric acid solution used is 1.5 times the total mass of iron and manganese in the leached residue, the acid dissolution temperature is 60° C., and the acid dissolution time is 4 h, to obtain ferromanganese phosphate liquid and acid-dissolved residue,

[0120] The obtained ferromanganese phosphate liquid and sodium hydroxide solution were slowly introduced into the reaction kettle, the flow rate of the ferromanganese phosphate liquid was 3 mL / min, the pH of the system was maintained at 4-4.5 as measured by a pH meter, and the first precipitation reaction was carried out at 50° C. for 6 hours to obtain a ferromanganese phosphate product;

[0121] The leachate obtained in step (2) is added with liquid alkali sodium hydroxide to adjust the pH to 6 to obtain a lithium-rich solution after impurities are removed, and a precipitant sodium carbonate is added (the amount of sodium carbonate added is 1.5 times the theoretical mass amount of lithium salt required in the lithium-rich solution) to carry out a second precipitation reaction at 90° C. for 3 hours to obtain lithium salt lithium carbonate.

[0122] Comparative Example 2

[0123] (1) 100 g of lithium manganese iron phosphate waste was mixed with a sulfuric acid solution (first acid solution) having a molar concentration of 1 mol / L to prepare a slurry, wherein the molar amount of sulfuric acid added was 1.5 times the theoretical amount (the theoretical amount was 0.5 times the total molar amount of lithium in the prepared slurry), sulfur dioxide and oxygen were introduced, and oxidative leaching was performed at 50° C. for 4 h, wherein the flow rate of sulfur dioxide was 25 L / h, and the flow rate of oxygen was 15 L / h, to obtain a leached slurry;

[0124] (2) filtering the leached slurry in step (1) to obtain a leaching solution and a leaching residue;

[0125] (3) mixing the washed leached residue of step (2) with a 1.2 mol / L sulfuric acid solution (second acid solution) for acid dissolution treatment, wherein the amount of sulfuric acid solution used is 1.5 times the total mass of iron and manganese in the leached residue, the acid dissolution temperature is 60° C., and the acid dissolution time is 4 h, to obtain ferromanganese phosphate liquid and acid-dissolved residue,

[0126] The obtained ferromanganese phosphate liquid and sodium hydroxide solution were slowly introduced into the reaction kettle, the flow rate of the ferromanganese phosphate liquid was 3 mL / min, the pH of the system was maintained at 4-4.5 as measured by a pH meter, and the first precipitation reaction was carried out at 50° C. for 6 hours to obtain a ferromanganese phosphate product;

[0127] The leachate obtained in step (2) is added with liquid alkali sodium hydroxide to adjust the pH to 6 to obtain a lithium-rich solution after impurities are removed, and a precipitant sodium carbonate is added (the amount of sodium carbonate added is 1.5 times the theoretical mass amount of lithium salt required in the lithium-rich solution) to carry out a second precipitation reaction at 90° C. for 3 hours to obtain lithium salt lithium carbonate.

[0128] Comparative Example 3

[0129] The difference between this comparative example and Example 1 is that in step (1) of this comparative example, sulfur dioxide gas is not introduced but only oxygen is introduced.

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

[0131] Comparative Example 4

[0132] The difference between this comparative example and Example 1 is that in step (1) of this comparative example, no oxygen is introduced but only sulfur dioxide gas is introduced.

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

[0134] Comparative Example 5

[0135] The difference between this comparative example and Example 1 is that in step (2) of this comparative example, an equal amount of iron powder is added as a copper removing agent.

[0136] The rest of the preparation methods and parameters were the same as those in Example 1.

[0137] The purity and impurity content of the lithium salts recovered in Examples 1-9 and Comparative Examples 1-5 were tested. The test results are shown in Table 1.

[0138] Table 1

[0139]

[0140] The component content of the ferromanganese phosphate recovered from Example 1-9 and Comparative Example 1-5 was analyzed, and the analysis and test results are shown in Table 2.

[0141] Table 2

[0142]

[0143]

[0144]

[0145]

[0146] The recovery method provided by the present invention utilizes the action of sulfur dioxide and oxygen in a mixed system of lithium iron manganese phosphate waste and a first acid solution to generate strong oxidizing free radical ions with a high redox potential, which can remove Fe in the lithium iron phosphate waste. 2+ and Mn 2+ The oxidation is carried out with excellent oxidation effect, which not only increases the valence state of manganese in lithium iron manganese phosphate and makes manganese precipitate in the leaching residue, but also realizes the selective extraction of lithium in lithium iron manganese phosphate, avoiding the problem of introducing a large amount of cationic impurities when using strong oxidants such as persulfate; the leaching slurry after oxidation leaching is subjected to deep copper removal treatment to reduce the copper and aluminum impurity content in the obtained leaching residue, thereby obtaining high-purity leaching residue and leachate; the leaching residue is then mixed with the second acid solution, and the pH value is adjusted to carry out the first precipitation reaction, so as to obtain the precursor manganese phosphate product required for the battery-grade lithium iron manganese phosphate positive electrode material; and after the leaching solution is subjected to lithium extraction treatment, a battery-grade purified lithium salt material can be obtained.

[0147] The applicant declares that the above is only a specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention shall fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for recycling lithium iron manganese phosphate waste, characterized in that: The recovery method comprises the following steps: (1) mixing the lithium iron manganese phosphate waste with the first acid solution, introducing sulfur dioxide and oxygen to perform oxidation leaching to obtain a leached slurry; (2) removing copper from the leached slurry to obtain leached residue and leaching liquid; (3) mixing the leached residue of step (2) with the second acid solution, adjusting the pH value to carry out a first precipitation reaction to obtain ferromanganese phosphate; and subjecting the leached solution of step (2) to lithium extraction treatment to obtain purified lithium salt.

2. The recycling method according to claim 1, characterized in that: Step (1) The concentration of the first acid solution is 1 to 5 mol / L; Preferably, the molar amount of the acid added in the first acid solution in step (1) is 1 to 2 times the theoretical amount.

3. The recovery method according to claim 1 or 2, characterized in that: The sulfur dioxide introduction rate is 20 to 50 L / h.

4. The recycling method according to any one of claims 1 to 3, characterized in that: The oxygen inlet flow rate is 10 to 30 L / h.

5. The recycling method according to any one of claims 1 to 4, characterized in that: The copper removal agent used in the copper removal process of step (2) comprises a compound containing thiomolybdate ions, and the compound containing thiomolybdate ions comprises ammonium tetrathiomolybdate; Preferably, in the copper removal process of step (2), the amount of copper removal agent used is 1 to 2 times the mass of copper in the leaching slurry.

6. The recycling method according to any one of claims 1 to 5, characterized in that: The leached residue after the copper removal treatment in step (2) is sequentially subjected to acid washing and water washing.

7. The recycling method according to any one of claims 1 to 6, characterized in that: Step (3) the concentration of the second acid solution is 1 to 5 mol / L; Preferably, in step (3), the leached residue in step (2) is mixed with the second acid solution to obtain ferromanganese phosphate liquid and acid-soluble residue; Preferably, the pH value adjusted in step (3) is to adjust the pH value of the ferromanganese phosphate solution; Preferably, after adjusting the pH value in step (3), the pH value in the system is maintained at 4-5.

8. The recycling method according to any one of claims 1 to 7, characterized in that: The lithium extraction method in step (3) comprises: The leaching solution in step (2) is decontaminated to obtain a lithium-rich solution, and the lithium-rich solution is subjected to a second precipitation reaction to obtain purified lithium salt.

9. The recycling method according to claim 8, characterized in that: The pH value of the impurity removal process is 5-6.

10. The recycling method according to claim 1, characterized in that: The recovery method comprises the following steps: (1) mixing the lithium iron manganese phosphate waste with the first acid solution, introducing sulfur dioxide at a flow rate of 20 to 50 L / h and oxygen at a flow rate of 10 to 30 L / h, and performing oxidative leaching to obtain a leached slurry; (2) removing copper from the leached slurry using ammonium tetrathiomolybdate to obtain a leached residue and a leached solution after the copper is removed, and acid-washing and water-washing the leached residue after the copper is removed to obtain a washed leached residue; (3) mixing the washed leached residue of step (2) with the second acid solution to obtain ferromanganese phosphate liquid and acid-soluble residue, adjusting the pH value of the ferromanganese phosphate liquid to 4 to 5, maintaining the pH value of the system at 4 to 5 to perform a first precipitation reaction to obtain ferromanganese phosphate; The leaching solution in step (2) is decontaminated under a pH value of 5 to 6 to obtain a lithium-rich solution, and the lithium-rich solution is subjected to a second precipitation reaction to obtain purified lithium salt.

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