CN115611250B - Method for recycling high-purity ferric phosphate from waste lithium iron phosphate positive electrode powder - Google Patents
Method for recycling high-purity ferric phosphate from waste lithium iron phosphate positive electrode powder Download PDFInfo
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- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 title claims abstract description 109
- 238000000034 method Methods 0.000 title claims abstract description 81
- 239000005955 Ferric phosphate Substances 0.000 title claims abstract description 75
- 229940032958 ferric phosphate Drugs 0.000 title claims abstract description 75
- 229910000399 iron(III) phosphate Inorganic materials 0.000 title claims abstract description 75
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 55
- 239000002699 waste material Substances 0.000 title claims abstract description 54
- 239000000843 powder Substances 0.000 title claims abstract description 51
- 238000004064 recycling Methods 0.000 title abstract description 21
- 238000002386 leaching Methods 0.000 claims abstract description 67
- 239000002253 acid Substances 0.000 claims abstract description 64
- 238000001556 precipitation Methods 0.000 claims abstract description 46
- 238000004321 preservation Methods 0.000 claims abstract description 26
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 17
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 46
- 239000007788 liquid Substances 0.000 claims description 46
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 36
- 229910000398 iron phosphate Inorganic materials 0.000 claims description 34
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 33
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 32
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 22
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 20
- 238000000926 separation method Methods 0.000 claims description 18
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 16
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 16
- 239000011575 calcium Substances 0.000 claims description 16
- 229910052791 calcium Inorganic materials 0.000 claims description 16
- 239000011777 magnesium Substances 0.000 claims description 16
- 229910052749 magnesium Inorganic materials 0.000 claims description 16
- 229910052759 nickel Inorganic materials 0.000 claims description 16
- 229910052782 aluminium Inorganic materials 0.000 claims description 15
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 15
- 239000011701 zinc Substances 0.000 claims description 15
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 claims description 14
- 239000010949 copper Substances 0.000 claims description 14
- 229910052742 iron Inorganic materials 0.000 claims description 14
- 238000002156 mixing Methods 0.000 claims description 14
- 229910052725 zinc Inorganic materials 0.000 claims description 14
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 13
- 229910052802 copper Inorganic materials 0.000 claims description 13
- 239000000047 product Substances 0.000 claims description 11
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 10
- 238000011534 incubation Methods 0.000 claims description 7
- 239000012043 crude product Substances 0.000 claims description 6
- 229910052739 hydrogen Inorganic materials 0.000 claims description 5
- 238000009413 insulation Methods 0.000 claims description 3
- 239000012535 impurity Substances 0.000 abstract description 34
- 239000003153 chemical reaction reagent Substances 0.000 abstract 1
- 230000003647 oxidation Effects 0.000 abstract 1
- 230000000052 comparative effect Effects 0.000 description 18
- 238000011084 recovery Methods 0.000 description 18
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- 238000001914 filtration Methods 0.000 description 10
- 238000001027 hydrothermal synthesis Methods 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 3
- 239000000706 filtrate Substances 0.000 description 3
- 229910001385 heavy metal Inorganic materials 0.000 description 3
- 239000011574 phosphorus Substances 0.000 description 3
- 229910052698 phosphorus Inorganic materials 0.000 description 3
- 238000004062 sedimentation Methods 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 2
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 229910001448 ferrous ion Inorganic materials 0.000 description 2
- 238000009616 inductively coupled plasma Methods 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- -1 separators Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 description 1
- CYJRNFFLTBEQSQ-UHFFFAOYSA-N 8-(3-methyl-1-benzothiophen-5-yl)-N-(4-methylsulfonylpyridin-3-yl)quinoxalin-6-amine Chemical compound CS(=O)(=O)C1=C(C=NC=C1)NC=1C=C2N=CC=NC2=C(C=1)C=1C=CC2=C(C(=CS2)C)C=1 CYJRNFFLTBEQSQ-UHFFFAOYSA-N 0.000 description 1
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 1
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 1
- UCKMPCXJQFINFW-UHFFFAOYSA-N Sulphide Chemical compound [S-2] UCKMPCXJQFINFW-UHFFFAOYSA-N 0.000 description 1
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 238000005119 centrifugation Methods 0.000 description 1
- 239000000084 colloidal system Substances 0.000 description 1
- 238000010668 complexation reaction Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 229940116007 ferrous phosphate Drugs 0.000 description 1
- 235000003891 ferrous sulphate Nutrition 0.000 description 1
- 239000011790 ferrous sulphate Substances 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 description 1
- 229910000155 iron(II) phosphate Inorganic materials 0.000 description 1
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 1
- SDEKDNPYZOERBP-UHFFFAOYSA-H iron(ii) phosphate Chemical compound [Fe+2].[Fe+2].[Fe+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O SDEKDNPYZOERBP-UHFFFAOYSA-H 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000005374 membrane filtration Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910000000 metal hydroxide Inorganic materials 0.000 description 1
- 150000004692 metal hydroxides Chemical class 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 150000007522 mineralic acids Chemical class 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000010452 phosphate Substances 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000011591 potassium Substances 0.000 description 1
- 229910052700 potassium Inorganic materials 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000001953 recrystallisation Methods 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 230000008929 regeneration Effects 0.000 description 1
- 238000011069 regeneration method Methods 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 229910052708 sodium Inorganic materials 0.000 description 1
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/37—Phosphates of heavy metals
- C01B25/375—Phosphates of heavy metals of iron
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/80—Compositional purity
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
- Y02W30/00—Technologies for solid waste management
- Y02W30/50—Reuse, recycling or recovery technologies
- Y02W30/84—Recycling of batteries or fuel cells
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The invention discloses a method for recycling high-purity ferric phosphate from waste lithium iron phosphate positive electrode powder. The method can obtain the high-purity ferric phosphate by acid leaching, oxidation, heat preservation, self-precipitation and other steps, does not need to add other impurity removing reagents, has low treatment cost, generates less waste after treatment, has little influence on environment, and is a feasible method for recycling the high-purity ferric phosphate from the waste lithium iron phosphate anode powder.
Description
Technical Field
The invention relates to the technical field of lithium battery recovery, in particular to a method for recovering high-purity ferric phosphate from waste lithium iron phosphate anode powder.
Background
At present, the quantity of retired power lithium ion batteries is huge, wherein the proportion of the retired lithium iron phosphate batteries is always more than 70%. Since lithium iron phosphate batteries contain valuable but harmful substances such as positive electrodes, negative electrodes, electrolytes, separators, binders (PVDF), etc., it is the focus of current research to employ appropriate recycling techniques to utilize the valuable components therein.
The economic value of the waste lithium iron phosphate positive electrode powder in the retired battery is higher, and the method is the key point of recycling the battery. The recovery and regeneration process of lithium element is simpler, and more mature technologies exist, but the recovery and treatment technology of iron and phosphorus needs to be further improved. Iron and phosphorus recovery is generally realized through acid dissolution and neutralization precipitation, but impurities such as aluminum, copper, nickel, magnesium, zinc, calcium and the like can be jointly separated out along with iron phosphate precipitation to influence the purity of iron phosphate products, so that the recovery of high-purity iron phosphate from waste lithium iron phosphate positive electrode powder is always a difficult point in the process of recycling waste lithium iron phosphate.
CN102610813a discloses a method for removing impurities in lithium iron phosphateThe method is to soak the carbon-coated lithium iron phosphate material in inorganic acid solution with pH value of 3.5-8.0 without damaging LiFePO 4 The Fe in the alloy dissolves Fe simple substance, feO and Fe 2 O 3 、Fe 2 P and other impurities, removing the organic impurities by using an organic solvent such as NMP/ethanol and the like, filtering, and calcining and decarbonizing at 400-600 ℃ to achieve the effect of effectively removing impurities. However, the impurity removal process is only aimed at carbon powder and Fe impurities, and has no obvious effect of removing common impurities such as Al, cu and the like in the raw materials, and has poor universality.
CN103086341a discloses a method for preparing battery grade ferric phosphate from ferrophosphorus, which refers to a method for obtaining ferric phosphate by leaching ferrophosphorus, performing operations such as recrystallization, membrane filtration, carbon adsorption, complexation concealment and the like on filtrate to remove impurity elements such as silicon, manganese, calcium, magnesium, potassium and sodium, and then inducing crystallization. The method can effectively obtain the high-purity ferric phosphate product, but has more impurity removal procedures and complex flow.
CN107902637a discloses a method for producing high-purity ferric phosphate, which uses industrial ferrous sulfate as raw material, and after dissolving, removing impurities, oxidizing Fe (ii) therein, and precipitating high-purity ferric phosphate. The method mainly comprises three times of impurity removal, wherein the first impurity removal is to adjust the pH of the solution, add soluble sulfide for continuous reaction, add flocculant after the reaction is finished, remove heavy metal (Zn) 2+ 、Cu 2+ 、Pb 2+ 、Hg 2+ Etc.) impurities; adding fluoride into the filtrate to remove calcium and magnesium impurities; and the third impurity removal is to add phosphoric acid into the secondary filtrate to form ferrous phosphate colloid in the system to adsorb trace heavy metal precipitate and fluoride precipitate in the solution. The method has complex impurity removal process and can generate a large amount of heavy metal solid wastes.
Therefore, there is a need to develop a method for recovering a high-purity iron phosphate product from a waste lithium iron phosphate positive electrode powder containing impurities in practice, which has the advantages of simple process flow, low treatment cost, less treated waste and small influence on environment.
Disclosure of Invention
In view of the problems existing in the prior art, the invention aims to provide a method for recycling high-purity ferric phosphate from waste lithium iron phosphate anode powder, the method is used for obtaining the high-purity ferric phosphate from the waste lithium iron phosphate anode powder through two-stage acid leaching, and the method is simple in process flow, low in treatment cost and suitable for large-scale industrial application.
To achieve the purpose, the invention adopts the following technical scheme:
the invention provides a method for recycling high-purity ferric phosphate from waste lithium iron phosphate anode powder, which comprises the following steps:
(1) Mixing waste lithium iron phosphate anode powder and a first acid solution, performing primary acid leaching at the temperature of-20-25 ℃, and performing solid-liquid separation to obtain leaching liquid;
(2) Mixing the leaching solution and the hydrogen peroxide solution, carrying out oxidation reaction, and sequentially carrying out first heat preservation self-precipitation and solid-liquid separation to obtain a crude product of ferric phosphate;
(3) Mixing crude iron phosphate and H + And (3) carrying out secondary acid leaching on the second acid solution with the concentration of 4-36 mol/L, and sequentially carrying out second heat preservation self-precipitation and solid-liquid separation to obtain the high-purity ferric phosphate.
The method adopts the waste lithium iron phosphate anode powder with the particle size of below 74 mu m, has large contact area with the first acid solution and is beneficial to the efficient leaching of iron and phosphorus; the primary acid leaching is carried out at a lower temperature of between 20 ℃ below zero and 25 ℃, and the leaching of metal aluminum mixed in the waste lithium iron phosphate positive electrode powder can be inhibited under the low temperature condition; the oxidation reaction is carried out by adopting a hydrogen peroxide solution, compared with the oxidant containing metal ions such as sodium persulfate, other impurity ions cannot be introduced, and the purity of the finally obtained ferric phosphate is further ensured; the crude ferric phosphate is mainly ferric phosphate dihydrate, and is shown in H + The second acid solution with the concentration of 4-36 mol/L can be well dissolved, so that the iron phosphate obtained after the second heat preservation and self precipitation has high yield and high purity.
The primary acid leaching in step (1) of the present invention is carried out at a temperature of-20 to 25℃and may be, for example, -20 ℃, -10 ℃, -5 ℃, -2 ℃, 0 ℃, 5 ℃, 10 ℃ or 25 ℃.
H in the second acid solution in the step (3) + The concentration is 4 to 36mol/L, and may be, for example, 4mol/L, 10mol/L, 15mol/L, 20mol/L, 25mol/L, 30mol/L, 33mol/L or 36mol/L.
The solid-liquid separation is not limited in the present invention, and any method known to those skilled in the art to be applicable to solid-liquid separation may be employed, and for example, filtration, sedimentation, centrifugation, or the like may be employed.
Preferably, the content of the ferric phosphate in the waste lithium iron phosphate positive electrode powder in the step (1) is not less than 50wt%, and for example, may be 50wt%, 55wt%, 60wt%, 70wt%, 80wt%, 85wt% or 95wt%.
Preferably, the waste lithium iron phosphate anode powder in the step (1) further contains impurities.
Preferably, the impurity comprises any one or a combination of at least two of an acid-insoluble separator, a plastic shell, and graphite powder, wherein typical but non-limiting combinations include a combination of a separator and a plastic shell, a combination of a plastic shell and graphite powder, or a combination of a separator, a plastic shell, and graphite powder.
Preferably, the impurities further comprise any one or a combination of at least two of an acid-soluble aluminum current collector, a copper current collector, nickel, magnesium, zinc, or calcium, wherein typical but non-limiting combinations include a combination of an aluminum current collector and a copper current collector, a combination of a copper current collector and nickel, a combination of nickel and magnesium, a combination of zinc and calcium, a combination of an aluminum current collector, a copper current collector and nickel, or a combination of nickel, magnesium, zinc, and calcium.
Preferably, the first acid solution in step (1) comprises any one or a combination of at least two of sulfuric acid solution, hydrochloric acid solution or phosphoric acid solution, wherein typical but non-limiting combinations include a combination of sulfuric acid solution and hydrochloric acid solution, a combination of hydrochloric acid solution and phosphoric acid solution or a combination of sulfuric acid solution, hydrochloric acid solution and phosphoric acid solution.
Preferably, H in the first acid solution + The concentration is 0.1 to 12mol/L, and may be, for example, 0.1mol/L, 1.0mol/L, 1.2mol/L, 1.5mol/L, 2mol/L, 3mol/L, 4mol/L, 6mol/L, 8mol/L, 10mol/L or 12mol/L.
Preferably, the solid-to-liquid ratio of the waste lithium iron phosphate positive electrode powder and the first acid solution in the step (1) is 1 (1-100) g/mL, for example, 1:1g/mL, 1:5g/mL, 1:10g/mL, 1:30g/mL, 1:50g/mL, 1:80g/mL or 1:100g/mL.
Preferably, the primary acid leaching time is 20-600 min, for example, 20min, 50min, 100min, 200min, 400min, 500min or 600min.
Preferably, the hydrogen peroxide solution of step (2) is used in an amount of 1.0 to 2.0 times its theoretical amount, which may be, for example, 1.0 times, 1.1 times, 1.3 times, 1.5 times, 1.8 times or 2.0 times.
The theoretical dosage of the hydrogen peroxide solution is the dosage when the molar ratio of the hydrogen peroxide to ferrous ions in the leaching solution is 1:2, and the method of the invention can completely oxidize the ferrous ions in the leaching solution and improve the yield of the finally obtained high-purity ferric phosphate.
Preferably, the hydrogen peroxide solution is added dropwise.
The hydrogen peroxide solution is preferably added into the leaching solution in a dropwise adding mode, so that the hydrogen peroxide solution is unstable and is easy to self-decompose, the self-decomposition consumption can be avoided to the greatest extent by adopting the dropwise adding mode, the utilization rate of the hydrogen peroxide is improved, and the treatment cost is saved.
Preferably, the dropping speed of the hydrogen peroxide solution is 1.0-10.0 mL/min, for example, 1.0mL/min, 2.0mL/min, 4.0mL/min, 5.0mL/min, 7.0mL/min or 10.0mL/min.
Preferably, the time of the oxidation reaction in the step (2) is 5 to 60min, for example, may be 5min, 10min, 20min, 30min, 50min or 60min.
Preferably, the temperature of the oxidation reaction is-20 to 60 ℃, and may be, for example, -20 ℃, -10 ℃, 0 ℃, 20 ℃, 30 ℃, 40 ℃, 50 ℃ or 60 ℃.
Preferably, the temperature of the first thermal self-precipitation in step (2) is 100 to 220 ℃, and may be, for example, 100 ℃, 130 ℃, 150 ℃, 180 ℃, 200 ℃ or 220 ℃.
Preferably, the time of the first thermal insulation self-precipitation is 30-720 min, for example, 30min, 80min, 100min, 150min, 300min, 400min, 500min, 600min or 720min.
Preferably, the first heat-preserving self-precipitation of step (2) is performed in a hydrothermal kettle.
The method can effectively remove the impurities which are insoluble in acid after primary acid leaching and solid-liquid separation; after the acid-soluble impurities enter a reaction system through primary acid leaching, after oxidation reaction, the equilibrium concentration of the impurity metal hydroxide or impurity phosphate is larger under the high acidity condition, the equilibrium concentration of the ferric phosphate is smaller, and most of the impurities are remained in the solution through the heat preservation self-precipitation process, so that the crude ferric phosphate is obtained.
The content of aluminum, copper, nickel, magnesium, zinc or calcium in the crude iron phosphate product is less than or equal to 1000ppm, and can be 1ppm, 10ppm, 30ppm, 50ppm, 100ppm, 300ppm, 500ppm, 800ppm or 1000ppm.
Preferably, the second acid solution of step (3) comprises any one or a combination of at least two of sulfuric acid solution, hydrochloric acid solution or phosphoric acid solution, wherein typical but non-limiting combinations include a combination of sulfuric acid solution and hydrochloric acid solution, a combination of hydrochloric acid solution and phosphoric acid solution or a combination of sulfuric acid solution, hydrochloric acid solution and phosphoric acid solution.
Preferably, the solid-to-liquid ratio of the secondary acid leaching is 1 (1-50) g/mL, and can be 1:1g/mL, 1:5g/mL, 1:10g/mL, 1:15g/mL, 1:20g/mL, 1:30g/mL or 1:50g/mL, for example.
Preferably, the temperature of the secondary acid leaching is 20 to 100 ℃, and may be, for example, 20 ℃, 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, or 100 ℃.
Preferably, the secondary acid leaching time is 1-72 h, for example, 1h, 5h, 10h, 20h, 50h, 60h, 70h or 72h.
Preferably, the temperature of the second thermal self-precipitation in step (3) is 110 to 250 ℃, for example 110 ℃, 130 ℃, 150 ℃, 180 ℃, 200 ℃, 220 ℃ or 250 ℃.
Preferably, the second thermal insulation self-precipitation time is 0.5-72 h, for example, 0.5h, 5h, 10h, 20h, 50h, 60h, 70h or 72h.
Preferably, the initial iron concentration of the second incubation self-precipitation is 0.1 to 3.0mol/L, and may be, for example, 0.1mol/L, 0.3mol/L, 0.5mol/L, 1.0mol/L, 1.5mol/L, 2.0mol/L, or 3.0mol/L.
Preferably, the second heat-preserving self-precipitation of the step (3) is performed in a hydrothermal reaction kettle.
The content of aluminum, copper, nickel, magnesium, zinc or calcium in the high-purity ferric phosphate obtained by the method is less than or equal to 50ppm, and can be 1ppm, 5ppm, 10ppm, 25ppm, 30ppm, 40ppm or 50ppm, for example.
The method obtains the crude product of the ferric phosphate through the primary impurity removal effect of the first heat preservation self-precipitation, and further achieves the deep impurity removal effect through the second heat preservation self-precipitation after redissolution. In the process of twice heat preservation and self-precipitation, the purification effect can be obviously improved through the matching of key process parameters such as temperature, time, acidity and the like, and the high-purity ferric phosphate is obtained.
The numerical ranges recited herein include not only the recited point values, but also any point values between the recited numerical ranges that are not recited, and are limited to, and for the sake of brevity, the invention is not intended to be exhaustive of the specific point values that the recited range includes.
As a preferred technical solution of the method according to the invention, the method comprises the steps of:
(1) Waste lithium iron phosphate positive electrode powder with solid-to-liquid ratio of 1 (1-100) g/mL and mixed ferric phosphate content not less than 50wt% and H + First acid solution with concentration of 0.1-12 mol/L is subjected to primary acid leaching for 20-600 min at the temperature of-20-25 ℃ and then is subjected to solid-liquid separation to obtain leaching liquid;
(2) Dropwise adding hydrogen peroxide solution into the leaching solution at a speed of 1.0-10.0 mL/min, carrying out oxidation reaction at a temperature of-20-60 ℃ for 5-60 min, carrying out self-precipitation at a first heat preservation temperature of 100-220 ℃ for 30-720 min, and carrying out solid-liquid separation to obtain a crude product of ferric phosphate; the dosage of the hydrogen peroxide is 1.0 to 2.0 times of the theoretical dosage;
(3) Mixing the crude iron phosphate and H according to the solid-to-liquid ratio of 1 (1-50) g/mL + A second acid solution with the concentration of 4 to 36mol/L at the temperature of 20 to 100 DEG CCarrying out secondary acid leaching for 1-72 h, carrying out secondary heat preservation self-precipitation for 0.5-72 h at 110-250 ℃, and carrying out solid-liquid separation to obtain high-purity ferric phosphate; the initial iron concentration of the second heat-preserving self-precipitation is 0.1-3.0 mol/L.
Compared with the prior art, the invention has the beneficial effects that:
(1) The method for recycling the high-purity ferric phosphate from the waste lithium iron phosphate positive electrode powder does not need to add an alkaline neutralizing agent or other impurity removing agents, has simple process flow and low treatment cost, and is suitable for large-scale popularization and application;
(2) The purity of the high-purity ferric phosphate obtained by the method for recycling the high-purity ferric phosphate from the waste lithium iron phosphate positive electrode powder can reach more than 99.91 percent, the recycling rate can reach more than 80 percent, and the contents of aluminum, copper, nickel, magnesium, zinc and calcium in the ferric phosphate product are all less than or equal to 50ppm.
Drawings
Fig. 1 is a process flow chart of a method for recycling high-purity ferric phosphate from waste lithium iron phosphate anode powder.
Detailed Description
The technical scheme of the invention is further described below by the specific embodiments with reference to the accompanying drawings.
The present invention will be described in further detail below. The following examples are merely illustrative of the present invention and are not intended to represent or limit the scope of the invention as defined in the claims.
The invention provides a method for recycling high-purity ferric phosphate from waste lithium iron phosphate anode powder, wherein a process flow chart of the method is shown in figure 1, and the method comprises the following steps of:
(1) Waste lithium iron phosphate positive electrode powder with solid-to-liquid ratio of 1 (1-100) g/mL and mixed ferric phosphate content not less than 50wt% and H + First acid solution with concentration of 0.1-12 mol/L is subjected to primary acid leaching for 20-600 min at the temperature of-20-25 ℃ and then is subjected to solid-liquid separation to obtain leaching liquid;
(2) Dropwise adding hydrogen peroxide solution into the leaching solution at a speed of 1.0-10.0 mL/min, carrying out oxidation reaction at a temperature of-20-60 ℃ for 5-60 min, carrying out self-precipitation at a first heat preservation temperature of 100-220 ℃ for 30-720 min, and carrying out solid-liquid separation to obtain a crude product of ferric phosphate; the dosage of the hydrogen peroxide is 1.0 to 2.0 times of the theoretical dosage;
(3) Mixing the crude iron phosphate and H according to the solid-to-liquid ratio of 1 (1-50) g/mL + Performing secondary acid leaching for 1-72 h at 20-100 ℃ with a second acid solution with the concentration of 4-36 mol/L, performing secondary heat preservation self-precipitation at 110-250 ℃ for 0.5-72 h, and performing solid-liquid separation to obtain high-purity ferric phosphate; the initial iron concentration of the second heat-preserving self-precipitation is 0.1-3.0 mol/L.
Example 1
The embodiment provides a method for recycling high-purity ferric phosphate from waste lithium iron phosphate anode powder, which comprises the following steps:
(1) Waste lithium iron phosphate positive electrode powder with 95wt% of mixed ferric phosphate content and H according to the solid-to-liquid ratio of 1:10g/mL + Carrying out primary acid leaching on a sulfuric acid solution with the concentration of 1.0mol/L at the temperature of minus 10 ℃ for 600min, and filtering to obtain leaching liquid; the waste lithium iron phosphate positive electrode powder contains 3.1% of aluminum, 0.08% of nickel, 0.1% of magnesium, 0.1% of zinc, 0.1% of calcium and 1.52% of graphite powder;
(2) Dropwise adding hydrogen peroxide solution into the leaching solution at a speed of 1.0mL/min, carrying out oxidation reaction at a temperature of 25 ℃ for 5min, and then carrying out self-precipitation in a hydrothermal reaction kettle for 600min through a first heat preservation at a temperature of 120 ℃, and filtering to obtain a crude iron phosphate product; the dosage of the hydrogen peroxide is 1.0 times of the theoretical dosage;
(3) Mixing the crude iron phosphate with H according to the solid-to-liquid ratio of 1:5g/mL + Carrying out secondary acid leaching on a sulfuric acid solution with the concentration of 12mol/L at 80 ℃ for 45h, carrying out secondary heat preservation self-precipitation at 150 ℃ for 6h, and filtering to obtain high-purity ferric phosphate; the initial iron concentration of the second incubation self-precipitation was 2.0mol/L.
Example 2
The embodiment provides a method for recycling high-purity ferric phosphate from waste lithium iron phosphate anode powder, which comprises the following steps:
(1) According toWaste lithium iron phosphate positive electrode powder with solid-to-liquid ratio of 1:30g/mL and mixed ferric phosphate content of 80wt% and H + Sulfuric acid solution with concentration of 0.3mol/L is subjected to primary acid leaching for 300min at 25 ℃, and then is filtered to obtain leaching solution; the waste lithium iron phosphate positive electrode powder contains 1.1% of aluminum, 0.6% of copper, 0.12% of nickel, 0.08% of magnesium, 0.06% of zinc, 0.04% of calcium and 18% of graphite powder;
(2) Dropwise adding hydrogen peroxide solution into the leaching solution at the speed of 6.0mL/min, carrying out oxidation reaction at the temperature of 30 ℃ for 20min, self-precipitating in a hydrothermal reaction kettle for 300min through first heat preservation at the temperature of 130 ℃, and filtering to obtain a crude iron phosphate product; the dosage of the hydrogen peroxide is 1.5 times of the theoretical dosage;
(3) Mixing the crude iron phosphate with H according to the solid-to-liquid ratio of 1:3g/mL + Carrying out secondary acid leaching on a sulfuric acid solution with the concentration of 28mol/L at the temperature of 40 ℃ for 3 hours, carrying out secondary heat preservation self-precipitation at the temperature of 120 ℃ for 12 hours, and filtering to obtain high-purity ferric phosphate; the initial iron concentration of the second incubation self-precipitation was 0.5mol/L.
Example 3
The embodiment provides a method for recycling high-purity ferric phosphate from waste lithium iron phosphate anode powder, which comprises the following steps:
(1) Waste lithium iron phosphate positive electrode powder with the content of mixed ferric phosphate of 60wt% and H according to the solid-to-liquid ratio of 1:13g/mL + Carrying out primary acid leaching on a sulfuric acid solution with the concentration of 1.5mol/L at the temperature of minus 20 ℃ for 100min, and filtering to obtain leaching liquid; the waste lithium iron phosphate positive electrode powder contains 5.6% of aluminum, 0.2% of nickel, 0.3% of magnesium, 0.1% of zinc, 0.08% of calcium and 33.72% of graphite powder;
(2) Dropwise adding hydrogen peroxide solution into the leaching solution at a speed of 10.0mL/min, carrying out oxidation reaction at a temperature of 60 ℃ for 60min, self-precipitating in a hydrothermal reaction kettle for 60min through a first heat preservation at a temperature of 220 ℃, and filtering to obtain a crude iron phosphate product; the dosage of the hydrogen peroxide is 2.0 times of the theoretical dosage;
(3) Mixing the crude iron phosphate with H according to the solid-to-liquid ratio of 1:5g/mL + Sulfuric acid solution with concentration of 20mol/L at 50 DEG CCarrying out secondary acid leaching for 5 hours under the condition, carrying out secondary heat preservation self-precipitation for 72 hours at the temperature of 250 ℃, and filtering to obtain high-purity ferric phosphate; the initial iron concentration of the second incubation self-precipitation was 2.5mol/L.
Example 4
The embodiment provides a method for recycling high-purity ferric phosphate from waste lithium iron phosphate anode powder, which comprises the following steps:
(1) Waste lithium iron phosphate positive electrode powder with 50wt% of mixed ferric phosphate content and H according to the solid-to-liquid ratio of 1:100g/mL + Phosphoric acid solution with the concentration of 0.1mol/L is subjected to primary acid leaching for 20min at the temperature of 5 ℃ and is centrifuged to obtain leaching solution; the waste lithium iron phosphate positive electrode powder contains 7.1% of aluminum, 1.0% of copper, 0.2% of nickel, 0.3% of magnesium, 0.1% of zinc, 0.08% of calcium and 31.22% of graphite powder;
(2) Dropwise adding hydrogen peroxide solution into the leaching solution at a speed of 3.0mL/min, carrying out oxidation reaction at the temperature of-20 ℃ for 50min, self-precipitating in a hydrothermal reaction kettle for 30min through a first heat preservation at the temperature of 100 ℃, and centrifuging to obtain a crude ferric phosphate product; the dosage of the hydrogen peroxide is 1.8 times of the theoretical dosage;
(3) Mixing the crude iron phosphate and H according to the solid-to-liquid ratio of 1:20g/mL + Performing secondary acid leaching on a concentrated hydrochloric acid solution with the concentration of 12mol/L at 20 ℃ for 10 hours, performing self-precipitation at 110 ℃ for 1 hour through a second heat preservation, and centrifuging to obtain high-purity ferric phosphate; the initial iron concentration of the second incubation self-precipitation is 3mol/L.
Example 5
The embodiment provides a method for recycling high-purity ferric phosphate from waste lithium iron phosphate anode powder, which comprises the following steps:
(1) Waste lithium iron phosphate positive electrode powder with 70wt% of mixed ferric phosphate content and H according to the solid-to-liquid ratio of 1:1g/mL + Nitric acid solution with the concentration of 12.0mol/L is subjected to primary acid leaching for 120min at 15 ℃, and then is settled to obtain leaching liquid; the waste lithium iron phosphate positive electrode powder contains 3.6% of aluminum, 1.2% of copper, 0.15% of nickel, 0.15% of magnesium, 0.15% of zinc, 0.2% of calcium and 24.55% of graphite powder;
(2) Dropwise adding hydrogen peroxide solution into the leaching solution at the speed of 4.0mL/min, carrying out oxidation reaction at the temperature of 0 ℃ for 30min, and then carrying out self-precipitation in a hydrothermal reaction kettle for 720min through a first heat preservation at the temperature of 150 ℃ to obtain a crude ferric phosphate product after sedimentation; the dosage of the hydrogen peroxide is 1.2 times of the theoretical dosage;
(3) Mixing the crude iron phosphate with H according to the solid-to-liquid ratio of 1:50g/mL + Performing secondary acid leaching on a nitric acid solution with the concentration of 4mol/L at the temperature of 100 ℃ for 1h, performing secondary heat preservation self-precipitation at the temperature of 170 ℃ for 0.5h, and obtaining high-purity ferric phosphate after sedimentation; the initial iron concentration of the second incubation self-precipitation was 0.1mol/L.
Example 6
This example provides a method for recovering high purity ferric phosphate from waste lithium iron phosphate positive electrode powder, which is the same as example 1 except that the hydrogen peroxide solution in step (2) is used in an amount 0.8 times the theoretical amount.
Example 7
This example provides a method for recovering high purity ferric phosphate from waste lithium iron phosphate positive electrode powder, which is the same as example 1 except that the hydrogen peroxide solution in step (2) is used in an amount 2.4 times the theoretical amount.
Comparative example 1
This comparative example provides a method for recovering high purity iron phosphate from waste lithium iron phosphate positive electrode powder, which is the same as example 1 except that the primary acid leaching temperature in step (1) is-30 ℃.
Comparative example 2
This comparative example provides a method for recovering high purity iron phosphate from waste lithium iron phosphate positive electrode powder, which is the same as example 1 except that the primary acid leaching temperature in step (1) is 30 ℃.
Comparative example 3
This comparative example provides a method for recovering high purity ferric phosphate from waste lithium iron phosphate positive electrode powder, which removes sulfuric acid solution H in step (3) + The concentration was the same as in example 1 except that the concentration was 1mol/L.
The impurity contents in the crude iron phosphate and the high-purity iron phosphate obtained in examples 1 to 3 were measured by using an ICP-5300 type inductively coupled plasma spectrometer, and the results are shown in tables 1 and 2, respectively.
TABLE 1
TABLE 2
As can be seen from tables 1 and 2:
the crude iron phosphate in examples 1 to 3 was subjected to secondary acid leaching and secondary heat-preserving self-precipitation to obtain a high-purity iron phosphate having a substantially reduced impurity content of 44ppm or less, 45ppm or less copper, 42ppm or less nickel, 45ppm or less magnesium, 38ppm or less zinc, and 40ppm or less calcium.
For reasons of economy, the impurity content data in the crude iron phosphate and the high purity iron phosphate in examples 4 to 7 and comparative examples 1 to 3 are not shown.
The purity of the high purity iron phosphate in the above examples and comparative examples was measured by ICP to obtain the results shown in table 3.
TABLE 3 Table 3
| Purity (%) | Recovery (%) | |
| Example 1 | 99.92％ | 94％ |
| Example 2 | 99.91％ | 92％ |
| Example 3 | 99.93％ | 92.5％ |
| Example 4 | 99.96％ | 87％ |
| Example 5 | 99.94％ | 88％ |
| Example 6 | 99.92％ | 81％ |
| Example 7 | 99.92％ | 94％ |
| Comparative example 1 | 99.92％ | 93％ |
| Comparative example 2 | 99.89％ | 94％ |
| Comparative example 3 | 99.10％ | 70％ |
From Table 3, the following points can be seen:
(1) Comprehensive examples 1-7 show that the purity of the high-purity ferric phosphate obtained by the method for recovering the high-purity ferric phosphate from the waste lithium iron phosphate anode powder can reach more than 99.91 percent, and the recovery rate can reach more than 80 percent;
(2) It can be seen from the combination of examples 1 and examples 6 to 7 that the hydrogen peroxide solution in step (2) of example 1 was used in an amount 1.0 times the theoretical amount thereof, and that the high-purity iron phosphate in example 1 was 99.92% in purity and 94% in recovery, and the high-purity iron phosphate in examples 6 to 7 was the same as in example 1, but the recovery of the high-purity iron phosphate finally obtained was reduced to 81% and the recovery of the high-purity iron phosphate in example 7 was 94% in comparison with the hydrogen peroxide solution in examples 6 to 7 which was 0.8 times and 2.4 times the theoretical amount thereof, respectively, since the divalent iron ions in the leachate was not completely oxidized in example 6, but the waste of the hydrogen peroxide solution was caused; therefore, the hydrogen peroxide solution in the step (2) is further preferably used in a specific range, so that the recovery rate of the high-purity ferric phosphate is improved, and the recovery treatment cost is saved;
(3) It can be seen from the combination of example 1 and comparative examples 1 to 2 that the temperature of the primary acid leaching in step (1) of example 1 is-10 ℃, compared with the temperatures of the primary acid leaching in comparative examples 1 to 2 of-30 ℃ and 30 ℃ respectively, the temperature in comparative example 1 is lower, the leaching of metallic aluminum mixed in the waste lithium iron phosphate positive electrode powder can be inhibited, the purity of the high-purity iron phosphate is 99.92%, the recovery rate is 93%, but the too low temperature condition can bring more refrigeration load, the recovery cost is increased, and the purity of the high-purity iron phosphate in comparative example 2 is slightly reduced to 99.89%; therefore, the method controls the temperature of acid leaching to be between 20 ℃ below zero and 25 ℃, and the obtained high-purity ferric phosphate has high purity, high recovery rate and low recovery treatment cost;
(4) As can be seen from a combination of example 1 and comparative example 3, sulfuric acid solution H in step (3) of example 1 + At a concentration of 12mol/L, compared with sulfuric acid solution H in step (3) of comparative example 3 + At a concentration of 1mol/L, the sulfuric acid solution H in step (3) was used in comparative example 3 + The concentration is too low, and the crude ferric phosphate is difficult to dissolve, so the purity of the obtained high-purity ferric phosphate is reduced to only 99.1 percent, and the recovery rate is greatly reduced to 70 percent; it is thus shown that the present invention controls H in the second acid solution + The concentration is 4-36 mol/L, and the high purity ferric phosphate finally obtained can be realized with high purity and high recovery rate.
In conclusion, the method for recycling the high-purity ferric phosphate from the waste lithium iron phosphate positive electrode powder provided by the invention has the advantages that the purity of the high-purity ferric phosphate is more than or equal to 99.9%, the recycling rate is more than 80%, the process flow is simple, the treatment cost is low, and the method is suitable for large-scale popularization and application.
The applicant declares that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that are easily conceivable within the technical scope of the present invention disclosed by the present invention fall within the scope of the present invention and the disclosure.
Claims (19)
1. The method for recovering high-purity ferric phosphate from waste lithium iron phosphate anode powder is characterized by comprising the following steps of:
(1) Mixing waste lithium iron phosphate anode powder and a first acid solution, performing primary acid leaching at the temperature of-20-25 ℃, and performing solid-liquid separation to obtain leaching liquid; the content of ferric phosphate in the waste lithium iron phosphate anode powder is not less than 50wt%;
(2) Mixing the leaching solution and the hydrogen peroxide solution, carrying out oxidation reaction, and sequentially carrying out first heat preservation self-precipitation and solid-liquid separation to obtain a crude product of ferric phosphate; the dosage of the hydrogen peroxide solution is 1.0 to 2.0 times of the theoretical dosage;
(3) Mixing crude iron phosphate and H + At a concentration of 12 to 36mol/LAnd (3) carrying out secondary acid leaching on the second acid solution, and sequentially carrying out second heat preservation self-precipitation and solid-liquid separation to obtain the high-purity ferric phosphate, wherein the contents of aluminum, copper, nickel, magnesium, zinc and calcium in the ferric phosphate product are less than or equal to 50ppm.
2. The method of claim 1, wherein the first acid solution of step (1) comprises any one or a combination of at least two of sulfuric acid solution, hydrochloric acid solution, or phosphoric acid solution.
3. The method of claim 1, wherein the first acid solution is H + The concentration is 0.1-12 mol/L.
4. The method of claim 1, wherein the solid-to-liquid ratio of the waste lithium iron phosphate positive electrode powder and the first acid solution in the step (1) is 1 (1-100) g/mL.
5. The method according to claim 1, wherein the primary acid leaching is for 20 to 600 minutes.
6. The method of claim 1, wherein the hydrogen peroxide solution is added dropwise.
7. The method of claim 1, wherein the hydrogen peroxide solution has a drop rate of 1.0 to 10.0mL/min.
8. The method according to any one of claims 1 to 5, wherein the time of the oxidation reaction in step (2) is 5 to 60 minutes.
9. The method according to claim 1, wherein the temperature of the oxidation reaction is-20 to 60 ℃.
10. The method according to any one of claims 1 to 6, wherein the temperature of the first thermal self-precipitation in step (2) is 100 to 220 ℃.
11. The method of claim 1, wherein the first thermal insulation self-precipitation time is 30 to 720 minutes.
12. The method of any one of claims 1-7, wherein the second acid solution of step (3) comprises any one or a combination of at least two of sulfuric acid solution, hydrochloric acid solution, or phosphoric acid solution.
13. The method according to claim 1, wherein the solid-to-liquid ratio of the secondary acid leaching is 1 (1-50) g/mL.
14. The method according to claim 1, wherein the temperature of the secondary acid leaching is 20-100 ℃.
15. The method according to claim 1, wherein the secondary acid leaching is for a period of 1 to 72 hours.
16. The method according to any one of claims 1 to 7, wherein the temperature of the second incubated self-precipitation of step (3) is 110 to 250 ℃.
17. The method of claim 1, wherein the second incubation self-precipitation time is 0.5 to 72 hours.
18. The method of claim 1, wherein the initial iron concentration of the second incubated self-precipitation is 0.1-3.0 mol/L.
19. The method according to claim 1, characterized in that it comprises the steps of:
(1) Waste lithium iron phosphate positive electrode powder with solid-to-liquid ratio of 1 (1-100) g/mL and mixed ferric phosphate content not less than 50wt% and H + First acid solution with concentration of 0.1-12 mol/L is subjected to primary acid leaching for 20-600 min at the temperature of-20-25 ℃ and then is subjected to solid-liquid separation to obtain leaching liquid;
(2) Dropwise adding hydrogen peroxide solution into the leaching solution at a speed of 1.0-10.0 mL/min, carrying out oxidation reaction at a temperature of-20-60 ℃ for 5-60 min, carrying out self-precipitation at a first heat preservation temperature of 100-220 ℃ for 30-720 min, and carrying out solid-liquid separation to obtain a crude product of ferric phosphate; the dosage of the hydrogen peroxide is 1.0 to 2.0 times of the theoretical dosage;
(3) Mixing the crude iron phosphate and H according to the solid-to-liquid ratio of 1 (1-50) g/mL + Performing secondary acid leaching for 1-72 h at 20-100 ℃ with a second acid solution with the concentration of 12-36 mol/L, performing secondary heat preservation self-precipitation at 110-250 ℃ for 0.5-72 h, and performing solid-liquid separation to obtain high-purity ferric phosphate; the initial iron concentration of the second heat-preserving self-precipitation is 0.1-3.0 mol/L.
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