CN115321505A - Method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater and application - Google Patents
Method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater and application Download PDFInfo
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- CN115321505A CN115321505A CN202210897000.0A CN202210897000A CN115321505A CN 115321505 A CN115321505 A CN 115321505A CN 202210897000 A CN202210897000 A CN 202210897000A CN 115321505 A CN115321505 A CN 115321505A
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- Prior art keywords
- lithium
- filtrate
- containing wastewater
- solid
- iron phosphate
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 83
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 82
- 239000002351 wastewater Substances 0.000 title claims abstract description 76
- 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 45
- 238000000034 method Methods 0.000 title claims abstract description 42
- 239000000706 filtrate Substances 0.000 claims abstract description 86
- 239000002893 slag Substances 0.000 claims abstract description 46
- 239000007788 liquid Substances 0.000 claims abstract description 37
- 238000000926 separation method Methods 0.000 claims abstract description 30
- 239000007787 solid Substances 0.000 claims abstract description 27
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims abstract description 26
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 21
- 238000006243 chemical reaction Methods 0.000 claims abstract description 21
- 239000011574 phosphorus Substances 0.000 claims abstract description 21
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 21
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 16
- 239000000203 mixture Substances 0.000 claims abstract description 15
- 238000002386 leaching Methods 0.000 claims abstract description 14
- 239000000047 product Substances 0.000 claims abstract description 14
- 238000005245 sintering Methods 0.000 claims abstract description 14
- 229910021529 ammonia Inorganic materials 0.000 claims abstract description 13
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 10
- 239000010452 phosphate Substances 0.000 claims abstract description 10
- 159000000003 magnesium salts Chemical class 0.000 claims abstract description 9
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims abstract description 9
- 238000002156 mixing Methods 0.000 claims abstract description 8
- 238000001035 drying Methods 0.000 claims abstract description 6
- 230000001502 supplementing effect Effects 0.000 claims abstract description 6
- DPTATFGPDCLUTF-UHFFFAOYSA-N phosphanylidyneiron Chemical compound [Fe]#P DPTATFGPDCLUTF-UHFFFAOYSA-N 0.000 claims abstract description 4
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 53
- 229910052742 iron Inorganic materials 0.000 claims description 20
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 16
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 16
- 238000004064 recycling Methods 0.000 claims description 11
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 claims description 9
- OEMGCAOEZNBNAE-UHFFFAOYSA-N [P].[Li] Chemical compound [P].[Li] OEMGCAOEZNBNAE-UHFFFAOYSA-N 0.000 claims description 9
- 229910001425 magnesium ion Inorganic materials 0.000 claims description 9
- ORUIBWPALBXDOA-UHFFFAOYSA-L magnesium fluoride Chemical compound [F-].[F-].[Mg+2] ORUIBWPALBXDOA-UHFFFAOYSA-L 0.000 claims description 6
- 229910001635 magnesium fluoride Inorganic materials 0.000 claims description 6
- 238000010979 pH adjustment Methods 0.000 claims description 6
- 230000002378 acidificating effect Effects 0.000 claims description 5
- 239000008394 flocculating agent Substances 0.000 claims description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 4
- 229910052760 oxygen Inorganic materials 0.000 claims description 4
- 239000001301 oxygen Substances 0.000 claims description 4
- 239000000126 substance Substances 0.000 claims description 4
- 238000002360 preparation method Methods 0.000 claims description 2
- 239000002253 acid Substances 0.000 abstract description 3
- 239000003513 alkali Substances 0.000 abstract description 2
- 230000003311 flocculating effect Effects 0.000 abstract 1
- CSNNHWWHGAXBCP-UHFFFAOYSA-L Magnesium sulfate Chemical compound [Mg+2].[O-][S+2]([O-])([O-])[O-] CSNNHWWHGAXBCP-UHFFFAOYSA-L 0.000 description 12
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 12
- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 12
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 description 11
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 10
- 229910052808 lithium carbonate Inorganic materials 0.000 description 10
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 10
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 9
- 229920002401 polyacrylamide Polymers 0.000 description 8
- 238000007789 sealing Methods 0.000 description 8
- 229910052759 nickel Inorganic materials 0.000 description 7
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 6
- 238000010438 heat treatment Methods 0.000 description 6
- 229910052943 magnesium sulfate Inorganic materials 0.000 description 6
- 235000019341 magnesium sulphate Nutrition 0.000 description 6
- 229910052748 manganese Inorganic materials 0.000 description 6
- 239000011572 manganese Substances 0.000 description 6
- 230000008569 process Effects 0.000 description 6
- 238000007873 sieving Methods 0.000 description 6
- 239000001488 sodium phosphate Substances 0.000 description 6
- 229910000162 sodium phosphate Inorganic materials 0.000 description 6
- 229910052938 sodium sulfate Inorganic materials 0.000 description 6
- 235000011152 sodium sulphate Nutrition 0.000 description 6
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 229910017052 cobalt Inorganic materials 0.000 description 5
- 239000010941 cobalt Substances 0.000 description 5
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 5
- 238000002425 crystallisation Methods 0.000 description 5
- 230000008025 crystallization Effects 0.000 description 5
- 238000001704 evaporation Methods 0.000 description 5
- 230000008020 evaporation Effects 0.000 description 5
- 239000007791 liquid phase Substances 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 4
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 description 4
- 229910000388 diammonium phosphate Inorganic materials 0.000 description 4
- 235000019838 diammonium phosphate Nutrition 0.000 description 4
- 238000007599 discharging Methods 0.000 description 4
- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical group [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 238000002791 soaking Methods 0.000 description 4
- 239000011343 solid material Substances 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 3
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 description 3
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 description 3
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 description 3
- -1 fluoride ions Chemical class 0.000 description 3
- 229910001386 lithium phosphate Inorganic materials 0.000 description 3
- 239000000347 magnesium hydroxide Substances 0.000 description 3
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 150000002739 metals Chemical class 0.000 description 3
- 235000019837 monoammonium phosphate Nutrition 0.000 description 3
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 description 3
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 2
- TWRXJAOTZQYOKJ-UHFFFAOYSA-L Magnesium chloride Chemical compound [Mg+2].[Cl-].[Cl-] TWRXJAOTZQYOKJ-UHFFFAOYSA-L 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 239000006230 acetylene black Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 229910000398 iron phosphate Inorganic materials 0.000 description 2
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 2
- 239000011777 magnesium Substances 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- YIXJRHPUWRPCBB-UHFFFAOYSA-N magnesium nitrate Chemical compound [Mg+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O YIXJRHPUWRPCBB-UHFFFAOYSA-N 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 229910000029 sodium carbonate Inorganic materials 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910052723 transition metal Inorganic materials 0.000 description 2
- LWIHDJKSTIGBAC-UHFFFAOYSA-K tripotassium phosphate Chemical compound [K+].[K+].[K+].[O-]P([O-])([O-])=O LWIHDJKSTIGBAC-UHFFFAOYSA-K 0.000 description 2
- PXGOKWXKJXAPGV-UHFFFAOYSA-N Fluorine Chemical compound FF PXGOKWXKJXAPGV-UHFFFAOYSA-N 0.000 description 1
- 229910018119 Li 3 PO 4 Inorganic materials 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 229910019440 Mg(OH) Inorganic materials 0.000 description 1
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- TWYAWLYZDNVYPT-UHFFFAOYSA-N dihexan-2-yl hydrogen phosphate Chemical compound CCCCC(C)OP(O)(=O)OC(C)CCCC TWYAWLYZDNVYPT-UHFFFAOYSA-N 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000004134 energy conservation Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 229960004887 ferric hydroxide Drugs 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 238000000227 grinding Methods 0.000 description 1
- 239000002920 hazardous waste Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 description 1
- 229910001629 magnesium chloride 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
- 238000005259 measurement Methods 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 229910017604 nitric acid Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 229910000160 potassium phosphate Inorganic materials 0.000 description 1
- 235000011009 potassium phosphates Nutrition 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000029219 regulation of pH Effects 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 229910001428 transition metal ion Inorganic materials 0.000 description 1
- 150000003624 transition metals Chemical class 0.000 description 1
- 238000004065 wastewater treatment Methods 0.000 description 1
Images
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-
- 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
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01D—COMPOUNDS OF ALKALI METALS, i.e. LITHIUM, SODIUM, POTASSIUM, RUBIDIUM, CAESIUM, OR FRANCIUM
- C01D5/00—Sulfates or sulfites of sodium, potassium or alkali metals in general
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/14—Magnesium hydroxide
- C01F5/20—Magnesium hydroxide by precipitation from solutions of magnesium salts with ammonia
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F5/00—Compounds of magnesium
- C01F5/26—Magnesium halides
- C01F5/28—Fluorides
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/54—Reclaiming serviceable parts of waste accumulators
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M6/00—Primary cells; Manufacture thereof
- H01M6/52—Reclaiming serviceable parts of waste cells or batteries, e.g. recycling
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Engineering & Computer Science (AREA)
- Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Geology (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
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Abstract
The invention discloses a method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater, which comprises the following steps: (1) Adding soluble magnesium salt into lithium-containing wastewater, performing solid-liquid separation to obtain filtrate A, adding alkali, and performing solid-liquid separation to obtain solid residue and filtrate B; (2) Adding soluble phosphate into the filtrate B, adding acid, performing Fenton reaction, flocculating, and performing solid-liquid separation to obtain lithium-containing phosphorus iron slag and filtrate C; (3) And (3) performing ammonia leaching on the solid slag, performing solid-liquid separation to obtain a filtrate D, mixing the filtrate D with the lithium-containing ferrophosphorus slag, supplementing a lithium source and a phosphorus source to obtain a mixture, performing hydrothermal reaction on the mixture, drying, and sintering to obtain a finished lithium iron phosphate product. The method can recover lithium in the lithium-containing wastewater to the maximum extent and prepare high-value additional products.
Description
Technical Field
The invention belongs to the technical field of wastewater treatment, and particularly relates to a method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater and application thereof.
Background
The lithium ion battery has the advantages of high voltage, good cyclicity, large energy density, small self-discharge, no memory effect and the like, is widely applied to the electronic and wireless communication industries, and is also the preferred power supply of the light high-capacity battery of the electric automobile in the future. As various electronic products have been gradually popularized and maintain a faster update speed, the demand of lithium ion batteries is increasing day by day, the quantity of waste lithium ion batteries and waste materials produced by lithium ion batteries is increasing day by day, and the waste containing valuable metals belongs to hazardous waste, so that the best way for solving the problem is to recycle and reuse resources.
At present, many researches on the recovery of valuable metals in waste lithium ion batteries are carried out, and the more traditional recovery method adopts an acid leaching process, namely leaching the valuable metals in an electrode material by using acids such as sulfuric acid, nitric acid, hydrochloric acid and the like. In the existing lixivium purification process, iron and aluminum are mostly removed by adopting oxidation to adjust pH, and then D is adopted 2 The impurity ions are separated from the Ni, co and Mn extracted by EHPA (di- (2-hexyl) phosphoric acid), and finally, in order to recover lithium, carbonate is added into raffinate to precipitate lithium. The raffinate contains a large amount of lithium and needs to be removed separately, and the lithium is precipitated by sodium carbonate in general, because the solubility product constant of lithium carbonate is 8.15 multiplied by 10 -4 The Li recovery rate is low, and a part of lithium in the wastewater is not recovered. In addition, the wastewater contains a partFluorine ions and residual transition metal ions are separated.
In the related art, lithium is mainly recovered as lithium carbonate in a method for recovering lithium in wastewater. However, the solubility of lithium carbonate in water is inversely proportional to the temperature, the solubility of lithium carbonate at 20 ℃ is high, and 1.33g of lithium carbonate can be dissolved in every 100g of water, so that the method can only obtain high recovery efficiency by heating lithium-containing wastewater with low concentration to 90 ℃ to precipitate lithium carbonate, which usually consumes a large amount of energy. In the related technology, although resources such as lithium and alkali in the lithium-containing wastewater can be recycled, the whole process is long, and the occupied area of a recycling instrument is large. Meanwhile, the solution is not subjected to decrement concentration before evaporation, so that the energy consumption is high, and the requirements of energy conservation and emission reduction are not met.
In summary, there is a need to develop a more rational recovery method for lithium-containing wastewater.
Disclosure of Invention
The present invention is directed to solving at least one of the problems of the prior art. Therefore, the invention provides a method for comprehensively recovering lithium-containing wastewater to prepare lithium iron phosphate and application thereof, and the method can recover lithium in the lithium-containing wastewater to the maximum extent and prepare high-value additional products.
The technical purpose of the invention is realized by the following technical scheme:
a method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater comprises the following steps:
(1) Adding soluble magnesium salt into lithium-containing wastewater, carrying out solid-liquid separation to obtain filtrate A and magnesium fluoride slag, adjusting the pH of the filtrate A to be alkaline, and carrying out solid-liquid separation to obtain solid slag and filtrate B;
(2) Adding soluble phosphate into the filtrate B, adjusting the pH of the filtrate B to be acidic, and then adding Fe 2+ And H 2 O 2 Performing Fenton reaction, adding a flocculating agent, and performing solid-liquid separation to obtain lithium-containing phosphorus iron slag and filtrate C;
(3) And (2) performing ammonia leaching on the solid slag obtained in the step (1) and performing solid-liquid separation to obtain a filtrate D, mixing the filtrate D with the lithium-containing phosphorus iron slag obtained in the step (2), supplementing a lithium source and a phosphorus source to obtain a mixture, performing hydrothermal reaction on the mixture, drying, and sintering to obtain a finished lithium iron phosphate product.
Preferably, the content of lithium in the lithium-containing wastewater in the step (1) is less than 8g/L.
Preferably, after soluble magnesium salt is added into the lithium-containing wastewater in the step (1), the content of magnesium ions in the lithium-containing wastewater is 0.03-0.15mol/L.
Further preferably, after soluble magnesium salt is added into the lithium-containing wastewater in the step (1), the content of magnesium ions in the lithium-containing wastewater is 0.05-0.10mol/L.
Preferably, the soluble magnesium salt is at least one of magnesium sulfate, magnesium chloride or magnesium nitrate, more preferably magnesium sulfate.
Preferably, the pH adjustment to be alkaline in the step (1) means that the pH is adjusted to 10 to 13.
Further preferably, the pH adjustment to be alkaline in the step (1) means that the pH is adjusted to 11.5 to 12.
Preferably, in the step (2), after the soluble phosphate is added into the filtrate B, the phosphorus content in the filtrate B is 0.01-0.50mol/L.
Further preferably, in the step (2), after the soluble phosphate is added to the filtrate B, the phosphorus content in the filtrate B is 0.01-0.20mol/L.
Preferably, in step (2), the soluble phosphate is at least one of sodium phosphate or potassium phosphate, more preferably sodium phosphate.
Preferably, in the step (2), the pH adjustment to be acidic means pH adjustment to be 3 to 5.5.
More preferably, in the step (2), the pH adjustment to be acidic means that the pH is adjusted to 3 to 4.
Preferably, in step (2), fe is added 2+ And H 2 O 2 In a molar ratio of (1-3): 1.
further preferably, in the step (2), fe is added 2+ And H 2 O 2 In a molar ratio of (1-1.5): 1.
preferably, in the step (2),after the Fenton reaction is carried out, the phosphorus content in the filtrate B is less than 10 -5 mol/L, and chemical oxygen demand is lower than 200mg/L.
Preferably, in the step (2), the addition amount of the flocculating agent is not less than 0.005g/L.
Further preferably, in the step (2), the addition amount of the flocculant is not less than 0.008g/L.
Preferably, the flocculant is a nonionic polymeric flocculant, more preferably polyacrylamide.
Preferably, in the step (2), the filtrate C can be directly discharged after pH regulation, or enter an MVR system for evaporation and crystallization to prepare anhydrous sodium sulphate and pure water.
Preferably, in the step (3), the solid-liquid ratio of the solid slag to the ammonia water in the ammonia leaching of the solid slag is 50-500g/L.
More preferably, in the step (3), the solid-liquid ratio of the solid slag to the ammonia water in the ammonia leaching of the solid slag is 50 to 300g/L.
Preferably, in the step (3), the concentration of ammonia water used for ammonia leaching of the solid slag is 4-10mol/L, and the ammonia leaching time is 1-3h.
More preferably, in the step (3), the concentration of ammonia water used for ammonia leaching of the solid residue is 4-6mol/L, and the ammonia leaching time is 1-2h.
Preferably, in the step (3), the ratio of lithium, phosphorus and iron elements in the mixture is (1.0-1.1): (0.95-1.0): (0.95-1.0).
Further preferably, in the step (3), the ratio of lithium, phosphorus and iron elements in the mixture is (1.0-1.05): (0.98-1.0): 0.98-1.0).
Preferably, in step (3), the lithium source is at least one of lithium carbonate, lithium hydroxide or lithium oxalate.
Preferably, in the step (3), the phosphorus source is at least one of ammonium monohydrogen phosphate, lithium phosphate, ammonium dihydrogen phosphate or phosphoric acid.
Preferably, in the step (3), the temperature of the hydrothermal reaction is 100-200 ℃ and the time is 1-20h.
Further preferably, in the step (3), the temperature of the hydrothermal reaction is 150-180 ℃ and the time is 3-15h.
Preferably, in step (3), the hydrothermal reaction is performed in a sealed environment.
Preferably, in the step (3), the drying is carried out by heating at 80-100 ℃ until the liquid phase is completely evaporated, and recovering ammonia water to return to the ammonia leaching link for use.
Preferably, in the step (3), the sintering is carried out in an inert atmosphere, the sintering temperature is 300-1000 ℃, and the time is 5-15h.
Further preferably, in the step (3), the sintering is carried out in an inert atmosphere, the sintering temperature is 500-850 ℃, and the time is 8-12h.
Preferably, in the step (3), the obtained material is further subjected to crushing, sieving and iron removal treatment after sintering.
Preferably, the method for preparing the lithium iron phosphate by comprehensively recovering the lithium-containing wastewater comprises the following steps:
(1) Adding magnesium sulfate into the lithium-containing wastewater to ensure that the content of magnesium ions in the wastewater is 0.05-0.10mol/L;
(2) Performing solid-liquid separation to obtain magnesium fluoride slag and filtrate A;
(3) Adjusting the pH value of the filtrate A to 11.5-12 by using sodium hydroxide, and performing solid-liquid separation to obtain solid slag and filtrate B;
(4) Adding sodium phosphate into the filtrate B to ensure that the phosphorus content in the filtrate B is 0.01-0.20mol/L;
(5) Adjusting pH of filtrate B to 3-4, adding Fe 2+ And H 2 O 2 Added Fe 2+ /H 2 O 2 The molar ratio is 1.0-1.5:1, performing Fenton reaction treatment on the filtrate B until the phosphorus content in the filtrate B is lower than 10-5mol/L and the COD (chemical oxygen demand) is lower than 200mg/L;
(6) Adding PAM into the filtrate B, wherein the addition amount of the PAM is not less than 0.008g/L, and the PAM refers to polyacrylamide;
(7) Performing solid-liquid separation to obtain lithium-phosphorus-containing iron slag and filtrate C, and directly discharging the filtrate C after regulating the pH value, or performing evaporative crystallization in an MVR system to prepare anhydrous sodium sulphate and pure water;
(8) Adding the solid residue obtained in the step (3) into 4-6mol/L ammonia water according to the solid-to-liquid ratio of 50-300g/L, soaking for 1-2h, and carrying out solid-liquid separation to obtain magnesium hydroxide residue and filtrate D;
(9) After mixing the filtrate D with the lithium-phosphorus-containing iron slag obtained in the step (7), supplementing a lithium source and a phosphorus source, so that Li: P: fe = (1.0-1.05): (0.98-1.0) in the mixture; the lithium source is lithium carbonate, lithium hydroxide and lithium oxalate, and the phosphorus source is ammonium monohydrogen phosphate, lithium phosphate, ammonium dihydrogen phosphate and phosphoric acid;
(10) Transferring the mixture into a reaction kettle, sealing, and carrying out hydrothermal reaction at 150-180 ℃ for 3-15h;
(11) After the hydrothermal reaction is finished, opening the reaction kettle for sealing, continuously heating at 80-100 ℃ until the liquid phase is completely evaporated, and recovering ammonia water;
(12) Sintering the solid material remained after evaporation for 8-12h at 500-850 ℃ in an inert atmosphere, and crushing, sieving and removing iron to obtain the finished product of the lithium iron phosphate.
The method is applied to the preparation of lithium iron phosphate or lithium batteries.
The beneficial effects of the invention are:
1. according to the method for preparing the lithium iron phosphate by comprehensively recovering the lithium-containing wastewater, firstly, a soluble magnesium salt is adopted to remove fluoride ions in the wastewater, then, the pH is adjusted to be alkaline, magnesium ions and nickel-cobalt-manganese transition metals in the magnesium ions are removed, then, excessive phosphate is added, lithium in the wastewater is further precipitated, the lithium content is reduced, the chemical oxygen demand of the wastewater is reduced through a Fenton reaction, meanwhile, redundant phosphate radicals are removed, an iron phosphate precipitate is formed, finally, the wastewater is further flocculated and settled through a flocculating agent, the lithium phosphate, the iron phosphate and the like are separated from the wastewater while the wastewater is purified, and a carbon source is provided for preparing the lithium iron phosphate in the next step;
2. in the method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater, solid slag is leached by ammonia water, after nickel, cobalt and manganese in the solid slag are dissolved, an ammonia-containing nickel, cobalt and manganese-containing solution is obtained and mixed with lithium-containing ferrophosphorus slag, the ammonia water is recovered by raw material supplement, hydrothermal reaction and evaporation, so that nickel, cobalt and manganese are used as doping elements, and a transition metal-doped lithium iron phosphate finished product is prepared by calcination, thereby recovering lithium, transition metal and the like in the wastewater, and further obtaining the high-added-value lithium iron phosphate cathode material.
The reaction principle is as follows:
adding soluble magnesium salt into lithium-containing wastewater: mg (magnesium) 2+ +2F - →MgF 2 ↓。
Adjust the pH of filtrate a to alkaline: mg (magnesium) 2+ +2OH - →Mg(OH) 2 ↓Me 2+ +2OH - →Me(OH) 2 ↓ (Me is at least one of Ni, co and Mn).
To filtrate B was added soluble phosphate: 3Li + +PO 4 3- →Li 3 PO 4 ↓。
Adding Fe 2+ And H 2 O 2 Performing a Fenton reaction: fe 3+ +PO 4 3- →FePO 4 ↓Fe 3+ +3OH - →Fe(OH) 3 ↓。
Ammonia leaching the solid slag: me (OH) 2 +6NH 3 →[Me(NH 3 ) 6 ](OH) 2 。
Carrying out hydrothermal reaction on the mixture, drying and sintering: li 3 PO 4 +3NH 3 ·H 2 O→3LiOH+(NH 4 ) 3 PO 4 [Me(NH 3 ) 6 ] 2+ +PO 4 3- →Me 3 (PO 4 ) 2 +6NH 3 4LiOH+4FePO 4 +C→4LiFePO 4 +CO 2 +2H 2 O。
Drawings
FIG. 1 is a schematic flow chart of example 1 of the present invention;
fig. 2 is an SEM image of lithium iron phosphate obtained in example 1 of the present invention.
Detailed Description
The present invention will be further described with reference to specific examples, in which the water quality of the lithium-containing wastewater used in examples 1 to 3 and comparative example 1 is as follows: 105.6g/L of sodium sulfate, 2.3g/L of sodium chloride, 5.9g/L of lithium, 5.2mg/L of total content of nickel, cobalt and manganese, 185.5mg/L of fluorine and 17000mg/L of COD.
Example 1:
a method for preparing lithium iron phosphate by comprehensively recycling lithium-containing wastewater, as shown in fig. 1, comprising the following steps:
(1) Adding magnesium sulfate into the lithium-containing wastewater to ensure that the content of magnesium ions in the wastewater is 0.05mol/L;
(2) Performing solid-liquid separation to obtain magnesium fluoride slag and filtrate A;
(3) Adjusting the pH value of the filtrate A to 11.5 by using sodium hydroxide, and carrying out solid-liquid separation to obtain solid slag and filtrate B;
(4) Adding sodium phosphate into the filtrate B to ensure that the phosphorus content in the filtrate B is 0.20mol/L;
(5) Adjusting pH of the filtrate B to 3.5, performing Fenton reaction on the filtrate B, and adding Fe 2+ And H 2 O 2 Added Fe 2+ /H 2 O 2 The molar ratio is 1.5:1 until the phosphorus content in the filtrate B is less than 10 -5 mol/L, COD is lower than 200mg/L;
(6) Adding PAM into the filtrate B, wherein the addition amount of PAM is 0.008g/L;
(7) Performing solid-liquid separation to obtain lithium-phosphorus-containing iron slag and filtrate C, and directly discharging the filtrate C after regulating the pH value, or performing evaporative crystallization in an MVR system to prepare anhydrous sodium sulphate and pure water;
(8) Adding the solid slag obtained in the step (3) into 4mol/L ammonia water according to the solid-liquid ratio of 50g/L, soaking for 1h, and carrying out solid-liquid separation to obtain magnesium hydroxide slag and filtrate D;
(9) Mixing the filtrate D with the lithium-phosphorus-containing iron slag obtained in the step (7), and then supplementing lithium carbonate and ammonium monohydrogen phosphate to ensure that the ratio of Li to P to Fe = 1.05;
(10) Transferring the mixture into a reaction kettle, sealing, and carrying out hydrothermal reaction for 3h at 180 ℃;
(11) After the hydrothermal reaction is finished, opening the reaction kettle for sealing, continuously heating at 100 ℃ until the liquid phase is completely evaporated, and recovering ammonia water;
(12) Sintering the evaporated residual solid material for 8 hours at 850 ℃ in an inert atmosphere, crushing, sieving and removing iron to obtain a finished lithium iron phosphate product, wherein an SEM image of the prepared finished lithium iron phosphate product is shown in figure 2.
Example 2:
a method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater comprises the following steps:
(1) Adding magnesium sulfate into the lithium-containing wastewater to ensure that the content of magnesium ions in the wastewater is 0.08mol/L;
(2) Performing solid-liquid separation to obtain magnesium fluoride slag and filtrate A;
(3) Adjusting the pH value of the filtrate A to 11.8 by using sodium hydroxide, and carrying out solid-liquid separation to obtain solid slag and filtrate B;
(4) Adding sodium phosphate into the filtrate B to ensure that the phosphorus content in the filtrate B is 0.10mol/L;
(5) Adjusting pH of the filtrate B to 3, performing Fenton reaction on the filtrate B, and adding Fe 2+ And H 2 O 2 Added Fe 2 + /H 2 O 2 The molar ratio is 1.3:1 until the phosphorus content in the filtrate B is less than 10 -5 mol/L, COD is lower than 200mg/L;
(6) Adding PAM into the filtrate B, wherein the addition amount of the PAM is 0.009g/L;
(7) Performing solid-liquid separation to obtain lithium-phosphorus-containing iron slag and filtrate C, and directly discharging the filtrate C after regulating the pH value or entering an MVR system for evaporation and crystallization to prepare anhydrous sodium sulphate and pure water;
(8) Adding the solid slag obtained in the step (3) into 5mol/L ammonia water according to the solid-liquid ratio of 150g/L, soaking for 1.5h, and carrying out solid-liquid separation to obtain magnesium hydroxide slag and filtrate D;
(9) Mixing the filtrate D with the lithium-phosphorus-containing iron slag obtained in the step (7), and then supplementing lithium hydroxide and ammonium dihydrogen phosphate to ensure that the ratio of Li to P to Fe = 1.03;
(10) Transferring the mixture into a reaction kettle, sealing, and carrying out hydrothermal reaction for 9 hours at 170 ℃;
(11) After the hydrothermal reaction is finished, opening the reaction kettle for sealing, continuously heating at 90 ℃ until the liquid phase is completely evaporated, and recovering ammonia water;
(12) And sintering the evaporated residual solid material for 10 hours at the temperature of 700 ℃ in an inert atmosphere, and crushing, sieving and removing iron to obtain a finished lithium iron phosphate product.
Example 3:
a method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater comprises the following steps:
(1) Adding magnesium sulfate into the lithium-containing wastewater to ensure that the content of magnesium ions in the wastewater is 0.10mol/L;
(2) Performing solid-liquid separation to obtain magnesium fluoride slag and filtrate A;
(3) Adjusting the pH value of the filtrate A to 12 by using sodium hydroxide, and carrying out solid-liquid separation to obtain solid slag and filtrate B;
(4) Adding sodium phosphate into the filtrate B to ensure that the phosphorus content in the filtrate B is 0.01mol/L;
(5) Adjusting pH of the filtrate B to 4, performing Fenton reaction on the filtrate B, and adding Fe 2+ And H 2 O 2 Added Fe 2 + /H 2 O 2 The molar ratio is 1.0:1 until the phosphorus content in the filtrate B is less than 10 -5 mol/L, COD is lower than 200mg/L;
(6) Adding PAM into the filtrate B, wherein the addition amount of PAM is 0.01g/L;
(7) Performing solid-liquid separation to obtain lithium-phosphorus-containing iron slag and filtrate C, and directly discharging the filtrate C after regulating the pH value, or performing evaporative crystallization in an MVR system to prepare anhydrous sodium sulphate and pure water;
(8) Adding the solid slag obtained in the step (3) into 6mol/L ammonia water according to the solid-to-liquid ratio of 300g/L, soaking for 2h, and carrying out solid-liquid separation to obtain magnesium hydroxide slag and filtrate D;
(9) After mixing the filtrate D with the lithium-phosphorus-containing iron slag obtained in the step (7), adding lithium oxalate and phosphoric acid, so that the ratio of Li to P to Fe = 1.0;
(10) Transferring the mixture into a reaction kettle, sealing, and carrying out hydrothermal reaction for 15 hours at 150 ℃;
(11) After the hydrothermal reaction is finished, opening the reaction kettle for sealing, continuously heating at 80 ℃ until the liquid phase is completely evaporated, and recovering ammonia water;
(12) And sintering the evaporated residual solid material for 12 hours at 500 ℃ in an inert atmosphere, and crushing, sieving and removing iron to obtain a finished lithium iron phosphate product.
Comparative example 1:
a method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater comprises the following steps:
(1) Adding sodium carbonate into the lithium-containing wastewater to enable the carbonate content in the wastewater to be 0.20mol/L, and carrying out solid-liquid separation to obtain carbonate;
(2) Adjusting the pH value of the wastewater to 4, carrying out Fenton reaction treatment on the wastewater, and adding Fe 2+ And H 2 O 2 Added Fe 2+ /H 2 O 2 The molar ratio is 1.5:1, the addition amount is the same as that of the example 1;
(3) Adding PAM into the wastewater, wherein the adding amount of the PAM is 0.008g/L;
(4) Solid-liquid separation, wherein the iron content of the wastewater is higher, the pH is lower than 4.6, and the wastewater cannot reach the standard to be discharged, and the solid enters the next working procedure;
(5) Mixing the obtained solid with lithium carbonate, ammonium monohydrogen phosphate and ferric hydroxide, wherein the ratio of Li to P to Fe = 1.05;
(6) Grinding the mixture for 2h, and drying at 150 ℃ for 4h;
(7) Sintering the dried material for 9 hours at 850 ℃ under inert atmosphere;
(8) And crushing, sieving and removing iron to obtain a finished product of the lithium iron phosphate.
Test example:
1. the water quality of the wastewater (filtrate C) discharged in the process of comprehensively recovering and preparing lithium iron phosphate in examples 1 to 3 and comparative example 1 was measured, and the measurement results are shown in table 1.
Table 1: and (3) detecting the water quality of the wastewater:
it can be known from table 1 that the content of Li in the wastewater discharged during the process of comprehensively recycling lithium-containing wastewater to prepare lithium iron phosphate by using the method for comprehensively recycling lithium-containing wastewater of the present invention is not more than 10.2mg/L, which is much less than the content of Li in the wastewater discharged during the process of comprehensively recycling lithium-containing wastewater of the present invention in comparison example 1, and that neither nickel, cobalt, manganese nor iron in the wastewater discharged during the process of comprehensively recycling lithium-containing wastewater to prepare lithium iron phosphate is detected by using the method for comprehensively recycling lithium-containing wastewater of the present invention, and F is not more than 7.8mg/L.
2. With the lithium iron phosphate positive electrode materials obtained in examples 1 to 3 and comparative example 1,acetylene black is used as a conductive agent, PVDF is used as a binder, the acetylene black and the PVDF are mixed according to a mass ratio of 8; the diaphragm is Celgard2400 polypropylene porous membrane; the solvent in the electrolyte is a solution composed of EC, DMC and EMC according to a mass ratio of 1 6 ，LiPF 6 The concentration of (b) is 1.0mol/L; a 2023 button cell battery was assembled in a glove box. The battery is subjected to charge-discharge cycle performance test, and 0.2C and 1C discharge specific capacities are tested within the range of cut-off voltage of 2.2-4.3V; the results of testing electrochemical performance are shown in table 2.
Table 2: electrochemical performance test results of the battery:
as can be seen from table 2, after the lithium iron phosphate prepared by the method for comprehensively recycling lithium-containing wastewater to prepare lithium iron phosphate of the present invention is assembled into a battery, the 0.2C discharge capacity can reach more than 147.6mAh/g, the 1C discharge capacity can reach more than 140.1mAh/g, and the electrochemical performance is superior to that of the lithium iron phosphate prepared by the method for comprehensively recycling lithium-containing wastewater to prepare lithium iron phosphate of comparative example 1.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. A method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater is characterized by comprising the following steps: the method comprises the following steps:
(1) Adding soluble magnesium salt into lithium-containing wastewater, carrying out solid-liquid separation to obtain filtrate A and magnesium fluoride slag, adjusting the pH of the filtrate A to be alkaline, and carrying out solid-liquid separation to obtain solid slag and filtrate B;
(2) Adding soluble phosphate into the filtrate B, adjusting the pH of the filtrate B to be acidic, and then adding Fe 2+ And H 2 O 2 Performing Fenton reaction, adding a flocculating agent, and performing solid-liquid separation to obtain lithium-phosphorus-containing iron slag and filtrate C;
(3) And (2) carrying out ammonia leaching on the solid slag obtained in the step (1) and then carrying out solid-liquid separation to obtain a filtrate D, mixing the filtrate D with the lithium-containing phosphorus iron slag obtained in the step (2), supplementing a lithium source and a phosphorus source to obtain a mixture, carrying out hydrothermal reaction on the mixture, drying and sintering to obtain a finished lithium iron phosphate product.
2. The method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater according to claim 1, which is characterized by comprising the following steps of: after soluble magnesium salt is added into the lithium-containing wastewater in the step (1), the content of magnesium ions in the lithium-containing wastewater is 0.03-0.15mol/L.
3. The method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater according to claim 1, which is characterized by comprising the following steps of: the pH adjustment in the step (1) to be alkaline means that the pH is adjusted to be 10-13.
4. The method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater according to claim 1, which is characterized by comprising the following steps of: in the step (2), after soluble phosphate is added into the filtrate B, the phosphorus content in the filtrate B is 0.01-0.50mol/L.
5. The method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater according to claim 1, which is characterized by comprising the following steps of: in the step (2), the pH value is adjusted to be acidic, namely the pH value is adjusted to be 3-5.5.
6. The method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater according to claim 1, which is characterized by comprising the following steps of: in the step (2), fe is added 2+ And H 2 O 2 Mole ofThe ratio is (1-3): 1.
7. the method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater according to claim 1, which is characterized by comprising the following steps of: in the step (2), after the Fenton reaction is carried out, the phosphorus content in the filtrate B is less than 10 -5 mol/L, and chemical oxygen demand is lower than 200mg/L.
8. The method for comprehensively recycling lithium-containing wastewater to prepare lithium iron phosphate according to claim 1, characterized by comprising the following steps: in the step (2), the addition amount of the flocculating agent is not less than 0.005g/L.
9. The method for preparing lithium iron phosphate by comprehensively recovering lithium-containing wastewater according to claim 1, which is characterized by comprising the following steps of: in the step (3), when the solid slag is subjected to ammonia leaching, the solid-liquid ratio of the solid slag to ammonia water is 50-500g/L.
10. Use of a method according to any one of claims 1 to 9 for the preparation of lithium iron phosphate or lithium batteries.
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