CN119194119A - Method for recycling rare earth in NdFeB waste based on ternary eutectic solvent - Google Patents
Method for recycling rare earth in NdFeB waste based on ternary eutectic solvent Download PDFInfo
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 94
- 150000002910 rare earth metals Chemical class 0.000 title claims abstract description 69
- 238000000034 method Methods 0.000 title claims abstract description 46
- 229910001172 neodymium magnet Inorganic materials 0.000 title claims abstract description 45
- 239000002699 waste material Substances 0.000 title claims abstract description 33
- 239000002904 solvent Substances 0.000 title abstract description 16
- 238000004064 recycling Methods 0.000 title abstract description 14
- 230000005496 eutectics Effects 0.000 title abstract description 7
- 238000000605 extraction Methods 0.000 claims abstract description 116
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 21
- 239000007788 liquid Substances 0.000 claims abstract description 18
- 229910001404 rare earth metal oxide Inorganic materials 0.000 claims abstract description 10
- MWKFXSUHUHTGQN-UHFFFAOYSA-N decan-1-ol Chemical compound CCCCCCCCCCO MWKFXSUHUHTGQN-UHFFFAOYSA-N 0.000 claims description 100
- HLZKNKRTKFSKGZ-UHFFFAOYSA-N tetradecan-1-ol Chemical compound CCCCCCCCCCCCCCO HLZKNKRTKFSKGZ-UHFFFAOYSA-N 0.000 claims description 86
- 238000000926 separation method Methods 0.000 claims description 30
- -1 rare earth ions Chemical class 0.000 claims description 26
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 24
- 229910017604 nitric acid Inorganic materials 0.000 claims description 24
- 239000003795 chemical substances by application Substances 0.000 claims description 17
- 238000006243 chemical reaction Methods 0.000 claims description 11
- 239000012071 phase Substances 0.000 claims description 10
- ZMBHCYHQLYEYDV-UHFFFAOYSA-N trioctylphosphine oxide Chemical compound CCCCCCCCP(=O)(CCCCCCCC)CCCCCCCC ZMBHCYHQLYEYDV-UHFFFAOYSA-N 0.000 claims description 10
- 238000002360 preparation method Methods 0.000 claims description 9
- 239000000203 mixture Substances 0.000 claims description 8
- 239000008346 aqueous phase Substances 0.000 claims description 7
- 238000010438 heat treatment Methods 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- 229910052799 carbon Inorganic materials 0.000 claims description 5
- 239000002244 precipitate Substances 0.000 claims description 4
- 238000001354 calcination Methods 0.000 claims description 3
- 238000006555 catalytic reaction Methods 0.000 claims description 2
- 238000003837 high-temperature calcination Methods 0.000 claims description 2
- 230000005389 magnetism Effects 0.000 claims description 2
- 238000002386 leaching Methods 0.000 abstract description 27
- QJVKUMXDEUEQLH-UHFFFAOYSA-N [B].[Fe].[Nd] Chemical compound [B].[Fe].[Nd] QJVKUMXDEUEQLH-UHFFFAOYSA-N 0.000 abstract description 24
- 238000002474 experimental method Methods 0.000 abstract description 17
- 230000008569 process Effects 0.000 abstract description 16
- 239000012074 organic phase Substances 0.000 abstract description 13
- ZNCPFRVNHGOPAG-UHFFFAOYSA-L sodium oxalate Chemical compound [Na+].[Na+].[O-]C(=O)C([O-])=O ZNCPFRVNHGOPAG-UHFFFAOYSA-L 0.000 abstract description 10
- 229940039790 sodium oxalate Drugs 0.000 abstract description 10
- 231100000331 toxic Toxicity 0.000 abstract description 6
- 230000002588 toxic effect Effects 0.000 abstract description 6
- 238000005406 washing Methods 0.000 abstract description 5
- 150000001298 alcohols Chemical class 0.000 abstract description 4
- 239000008367 deionised water Substances 0.000 abstract description 4
- 229910021641 deionized water Inorganic materials 0.000 abstract description 4
- 239000012452 mother liquor Substances 0.000 abstract description 4
- MPQXHAGKBWFSNV-UHFFFAOYSA-N oxidophosphanium Chemical class [PH3]=O MPQXHAGKBWFSNV-UHFFFAOYSA-N 0.000 abstract 1
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 72
- 229910052742 iron Inorganic materials 0.000 description 42
- 229940043348 myristyl alcohol Drugs 0.000 description 36
- 229910052739 hydrogen Inorganic materials 0.000 description 30
- 239000001257 hydrogen Substances 0.000 description 30
- 239000000243 solution Substances 0.000 description 22
- 238000000638 solvent extraction Methods 0.000 description 17
- 230000035484 reaction time Effects 0.000 description 15
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 13
- 230000000694 effects Effects 0.000 description 13
- LQZZUXJYWNFBMV-UHFFFAOYSA-N dodecan-1-ol Chemical compound CCCCCCCCCCCCO LQZZUXJYWNFBMV-UHFFFAOYSA-N 0.000 description 11
- 239000003350 kerosene Substances 0.000 description 9
- 239000000370 acceptor Substances 0.000 description 8
- 239000002608 ionic liquid Substances 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 230000007246 mechanism Effects 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- 238000005185 salting out Methods 0.000 description 7
- 239000011734 sodium Substances 0.000 description 7
- 238000004458 analytical method Methods 0.000 description 6
- 239000012535 impurity Substances 0.000 description 6
- 150000002500 ions Chemical class 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 5
- 238000005421 electrostatic potential Methods 0.000 description 5
- 238000002354 inductively-coupled plasma atomic emission spectroscopy Methods 0.000 description 5
- 238000002329 infrared spectrum Methods 0.000 description 5
- 230000003993 interaction Effects 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 229910052692 Dysprosium Inorganic materials 0.000 description 4
- 238000001157 Fourier transform infrared spectrum Methods 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- 229910001447 ferric ion Inorganic materials 0.000 description 4
- 238000009854 hydrometallurgy Methods 0.000 description 4
- 238000011068 loading method Methods 0.000 description 4
- 238000001556 precipitation Methods 0.000 description 4
- 230000008929 regeneration Effects 0.000 description 4
- 238000011069 regeneration method Methods 0.000 description 4
- 238000012216 screening Methods 0.000 description 4
- 229910002651 NO3 Inorganic materials 0.000 description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 3
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 3
- 238000004364 calculation method Methods 0.000 description 3
- 230000008859 change Effects 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000007613 environmental effect Effects 0.000 description 3
- 230000002349 favourable effect Effects 0.000 description 3
- 239000012527 feed solution Substances 0.000 description 3
- 230000002209 hydrophobic effect Effects 0.000 description 3
- 238000000622 liquid--liquid extraction Methods 0.000 description 3
- 125000004430 oxygen atom Chemical group O* 0.000 description 3
- NOOLISFMXDJSKH-KXUCPTDWSA-N (-)-Menthol Chemical compound CC(C)[C@@H]1CC[C@@H](C)C[C@H]1O NOOLISFMXDJSKH-KXUCPTDWSA-N 0.000 description 2
- NOOLISFMXDJSKH-UHFFFAOYSA-N DL-menthol Natural products CC(C)C1CCC(C)CC1O NOOLISFMXDJSKH-UHFFFAOYSA-N 0.000 description 2
- 238000003775 Density Functional Theory Methods 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- 238000004566 IR spectroscopy Methods 0.000 description 2
- 229910052779 Neodymium Inorganic materials 0.000 description 2
- RDOXTESZEPMUJZ-UHFFFAOYSA-N anisole Chemical compound COC1=CC=CC=C1 RDOXTESZEPMUJZ-UHFFFAOYSA-N 0.000 description 2
- 125000004429 atom Chemical group 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- UFMZWBIQTDUYBN-UHFFFAOYSA-N cobalt dinitrate Chemical compound [Co+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O UFMZWBIQTDUYBN-UHFFFAOYSA-N 0.000 description 2
- 238000013478 data encryption standard Methods 0.000 description 2
- 235000014113 dietary fatty acids Nutrition 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000003912 environmental pollution Methods 0.000 description 2
- 239000000284 extract Substances 0.000 description 2
- 229930195729 fatty acid Natural products 0.000 description 2
- 239000000194 fatty acid Substances 0.000 description 2
- 150000004665 fatty acids Chemical class 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 229940039748 oxalate Drugs 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 238000000425 proton nuclear magnetic resonance spectrum Methods 0.000 description 2
- 150000003242 quaternary ammonium salts Chemical class 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 230000001172 regenerating effect Effects 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- KWIUHFFTVRNATP-UHFFFAOYSA-N Betaine Natural products C[N+](C)(C)CC([O-])=O KWIUHFFTVRNATP-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 238000004057 DFT-B3LYP calculation Methods 0.000 description 1
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 1
- 229910002554 Fe(NO3)3·9H2O Inorganic materials 0.000 description 1
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 1
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 1
- HEFNNWSXXWATRW-UHFFFAOYSA-N Ibuprofen Chemical compound CC(C)CC1=CC=C(C(C)C(O)=O)C=C1 HEFNNWSXXWATRW-UHFFFAOYSA-N 0.000 description 1
- KWIUHFFTVRNATP-UHFFFAOYSA-O N,N,N-trimethylglycinium Chemical compound C[N+](C)(C)CC(O)=O KWIUHFFTVRNATP-UHFFFAOYSA-O 0.000 description 1
- 229910003205 Nd(NO3)3·6H2O Inorganic materials 0.000 description 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 1
- 229910002828 Pr(NO3)3·6H2O Inorganic materials 0.000 description 1
- 229910052777 Praseodymium Inorganic materials 0.000 description 1
- 238000003916 acid precipitation Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 125000000217 alkyl group Chemical group 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 230000001174 ascending effect Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000002585 base Substances 0.000 description 1
- 229960003237 betaine Drugs 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 229910052729 chemical element Inorganic materials 0.000 description 1
- 239000012295 chemical reaction liquid Substances 0.000 description 1
- YOYGIPRFEXDEIU-UHFFFAOYSA-N chloro-trihexyl-tetradecyl-$l^{5}-phosphane Chemical compound CCCCCCCCCCCCCCP(Cl)(CCCCCC)(CCCCCC)CCCCCC YOYGIPRFEXDEIU-UHFFFAOYSA-N 0.000 description 1
- 230000000052 comparative effect Effects 0.000 description 1
- 238000010668 complexation reaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000002950 deficient Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010790 dilution Methods 0.000 description 1
- 239000012895 dilution Substances 0.000 description 1
- 238000004945 emulsification Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011067 equilibration Methods 0.000 description 1
- 239000000374 eutectic mixture Substances 0.000 description 1
- 238000004880 explosion Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- VEPSWGHMGZQCIN-UHFFFAOYSA-H ferric oxalate Chemical compound [Fe+3].[Fe+3].[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O.[O-]C(=O)C([O-])=O VEPSWGHMGZQCIN-UHFFFAOYSA-H 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 239000011737 fluorine Substances 0.000 description 1
- 229910052731 fluorine Inorganic materials 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 150000002431 hydrogen Chemical class 0.000 description 1
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 1
- 229960001680 ibuprofen Drugs 0.000 description 1
- 229910052738 indium Inorganic materials 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 238000011835 investigation Methods 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 231100000053 low toxicity Toxicity 0.000 description 1
- 238000013507 mapping Methods 0.000 description 1
- 229940041616 menthol Drugs 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- UZKWTJUDCOPSNM-UHFFFAOYSA-N methoxybenzene Substances CCCCOC=C UZKWTJUDCOPSNM-UHFFFAOYSA-N 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229930014626 natural product Natural products 0.000 description 1
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 description 1
- 231100000252 nontoxic Toxicity 0.000 description 1
- 230000003000 nontoxic effect Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 235000006408 oxalic acid Nutrition 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 125000004437 phosphorous atom Chemical group 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 230000005588 protonation Effects 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000009853 pyrometallurgy Methods 0.000 description 1
- 238000009877 rendering Methods 0.000 description 1
- 238000012958 reprocessing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 235000010344 sodium nitrate Nutrition 0.000 description 1
- 239000004317 sodium nitrate Substances 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
- 239000002351 wastewater Substances 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B59/00—Obtaining rare earth metals
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
- C22B3/262—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds using alcohols or phenols
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
- C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
- C22B3/26—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds
- C22B3/38—Treatment or purification of solutions, e.g. obtained by leaching by liquid-liquid extraction using organic compounds containing phosphorus
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B7/00—Working up raw materials other than ores, e.g. scrap, to produce non-ferrous metals and compounds thereof; Methods of a general interest or applied to the winning of more than two metals
- C22B7/005—Separation by a physical processing technique only, e.g. by mechanical breaking
-
- 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
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P10/00—Technologies related to metal processing
- Y02P10/20—Recycling
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Mechanical Engineering (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Environmental & Geological Engineering (AREA)
- Materials Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Geochemistry & Mineralogy (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The invention discloses a method for recycling rare earth in neodymium iron boron waste based on ternary eutectic solvents, which is used for preparing and characterizing 13 types of HDESs composed of three Xinji phosphine oxides (TOPO) as HBAs and alcohol compounds as HBDs, and is characterized in that a batch countercurrent extraction experiment is carried out under the optimal condition by taking actual leaching liquid as mother liquor, and HDES is used for three-stage countercurrent extraction, the total rare earth concentration in the mother liquor is reduced from 4389.3mg/L to 33.5mg/L, so that the rare earth is completely recycled, the loaded organic phase can be stripped through 0.2mol/L sodium oxalate, the HDES after back extraction can enter circulation after washing by deionized water, and the HDES still maintains good stability after five times of circulation. And the rare earth after back extraction can be baked to finally form rare earth oxide products. The process is green and clean, does not need to use toxic volatile solvents, and has wide application prospect.
Description
Technical Field
The invention belongs to the technical field of hydrometallurgy, and particularly relates to a method for recycling rare earth in neodymium iron boron waste based on ternary eutectic solvents.
Background
The importance of rare earth elements is self-evident, and the rare earth elements are key raw materials essential for advanced equipment manufacturing, new energy sources, new materials and other high-tech industries due to excellent magnetic, optical, electrical and chemical properties. At present, rare earth elements are mainly derived from mineral exploitation, but excessive exploitation can cause serious environmental pollution. Therefore, development of a new rare earth recycling system is urgently required.
In recent years, neodymium iron boron magnets are popular in the market due to their high energy density and low cost. The total demand of global rare earth permanent magnets is counted to be in an ascending trend in 2000 to 2017, wherein the neodymium-iron-boron permanent magnets account for more than 90%. The neodymium-iron-boron permanent magnet has wide application in the fields of wind driven generators, new energy automobiles and the like. It is known that neodymium-iron-boron permanent magnets are mainly composed of neodymium, iron and boron, wherein iron accounts for 60-70%. In addition, certain physical and magnetic properties thereof can be altered by the addition of other chemical elements (e.g., dy, tb, gd, nb, co, cu, ga) to accommodate a wide range of application requirements. In the production process, a large amount of raw material scraps, leftover materials and defective products can be generated due to the hard and brittle neodymium iron boron magnets. The service life of the NdFeB permanent magnet also depends on the application field. For example, the service life of a general electronic product is 2-3 years, and the service life of a wind driven generator is 20-30 years. Therefore, the waste neodymium-iron-boron permanent magnet becomes an important rare earth secondary resource. However, at present, no method for recycling the waste neodymium iron boron permanent magnet is relatively mature, economical and feasible. Therefore, how to recover rare earth from waste neodymium iron boron permanent magnets attracts more and more attention of students. The recycling method of the waste neodymium iron boron permanent magnet disclosed at present comprises direct recycling, alloy reprocessing after hydrogen explosion, hydrometallurgy, pyrometallurgy and the like. Where hydrometallurgy seems to be the best choice for spent neodymium iron boron magnet recovery, as hydrometallurgy can handle all types of permanent magnets. The hydrometallurgical treatment of the waste neodymium-iron-boron permanent magnet mainly comprises two links, namely leaching and rare earth separation. The leaching process is largely divided into complete leaching and selective leaching. However, even with selective leaching, it is difficult to limit the entry of impurity elements into the solution to affect the recovery of subsequent rare earths due to insufficient separation effects. The rare earth separation technology of the NdFeB permanent magnet waste mainly comprises a precipitation method, a solvent extraction method, an ionic liquid extraction method and the like. Rabatho et al recovered rare earth from neodymium iron boron magnetic waste mud by a selective precipitation method, removed iron by first adjusting the pH value for precipitation, then recovered rare earth by oxalic acid precipitation, and then calcined at high temperature to produce rare earth oxide products. The problem with this process is that iron precipitation results in a large rate of rare earth loss. The solvent extraction method is also used for recycling the waste neodymium-iron-boron permanent magnet due to the characteristics of strong continuity, high selectivity, more favorable industrialized operation and the like, but has the defects of easy emulsification, easy volatilization of solvent, large acid-base consumption, large wastewater discharge and the like, so that the further application of the method is limited. In view of environmental pollution caused by solvent extraction, in recent years, researchers have focused on turning to hydrophobic ionic liquids because of their advantages of low vapor pressure, high stability, wide liquid phase range, environmental friendliness, and the like. For example, xue et al designed and synthesized two carboxylic acid based ionic liquids ([ A336] [ BTA ] and [ A336] [ OTA ]) to efficiently extract Nd (III), koen Binnemans et al also proposed the use of undiluted fluorine free ionic liquid trihexyl (tetradecyl) phosphorus chloride to extract Fe (III) and Nd (III) from hydrochloric acid solutions. Although ionic liquids are more environmentally friendly than solvent extraction, their viscosity is much higher than that of solvent extraction, and the extraction process also needs to be carried out under the condition of high salting-out agent concentration to improve their extraction separation performance, and at the same time, the ionic liquid synthesis process is complex and purification is difficult, thus limiting their further application. The presence of the hydrophobic eutectic solvent (HDES) successfully solves the problems associated with ionic liquids. Generally, HDES is a eutectic mixture of two or more compounds consisting of a Hydrogen Bond Acceptor (HBA) and a Hydrogen Bond Donor (HBD). The preparation is simple, nontoxic, environment-friendly and relatively low in cost, and attracts more and more scholars attention in the field of liquid-liquid extraction. For example, van Osch et al were first looking for a hydrophobic nature of HDES and studied the extraction of volatile fatty acids from aqueous phase based on HDESs quaternary ammonium salts. Fan et al used natural products such as DL-menthol, anisole, etc. to prepare HDES to extract betaine in the aqueous phase. Tereshatove and the like expand the application of HDES In metal ion extraction, and the ibuprofen, menthol, quaternary ammonium salt and fatty acid composition HDES are adopted for the first time to extract and separate indium (In) In the aqueous phase.
Disclosure of Invention
In order to solve the above technical problems, the present invention provides HDES extractant, which includes trioctylphosphine oxide (TOPO), decanol (DA) and tetradecyl alcohol (MA).
According to an embodiment of the present invention, in the HDES extraction agent, the molar ratio of DA, MA, TOPO is (9:1:5) - (1:9:5), (5:5:3) - (5:5:7), and exemplary are 9:1:5, 7:3:5, 5:5:3, 5:5:4, 5:5:5, 3:7:5, 1:9:5, and preferably 5:5:4.
According to an embodiment of the invention, the water content of HDES extraction agent is lower than 3%, preferably 2.95% -2.0%.
According to the embodiment of the invention, the organic carbon content in the HDES extractant aqueous phase is less than 100mg/L, preferably 10-95 mg/L.
According to an embodiment of the invention, the HDES extractant has a viscosity of less than 40 mPa-s, preferably 30 to 39.9 mPa-s.
According to the embodiment of the invention, the density of HDES extractant is about 0.85g/cm -3, preferably 0.84-0.86 g/cm -3.
The invention provides a preparation method of the HDES extractant, which comprises the step of mixing trioctylphosphine oxide (TOPO), decyl Alcohol (DA) and tetradecyl alcohol (MA) to prepare the HDES extractant.
Preferably, the components are mixed in the molar ratios described above. According to an embodiment of the present invention, the preparation method further comprises heating the reaction liquid obtained by mixing. Preferably, the heating temperature is 40-80 ℃, and exemplary temperatures are 40 ℃, 60 ℃ and 80 ℃.
The invention also provides the HDES extractant for recovering rare earth elements in neodymium iron boron waste materials. Preferably for recovering rare earth elements from the leaching solution of the waste neodymium-iron-boron permanent magnet.
The invention also provides a method for recovering rare earth in neodymium iron boron waste by using the HDES extractant, which comprises the steps of mixing the HDES extractant with the neodymium iron boron waste, carrying out countercurrent extraction, separating to obtain HDES loaded with rare earth ions, carrying out back extraction by using a back extractant to obtain rare earth precipitate, and finally roasting at a high temperature to obtain rare earth oxide.
According to an embodiment of the invention, the stripping agent is selected from at least one of HNO 3, HCl or Na 2C2O4, preferably from Na 2C2O4.
According to an embodiment of the invention, the initial acidity of the NdFeB waste material liquid is 0.5-2.5mol/L, and is exemplified by 0.5mol/L, 1mol/L, 1.5mol/L, 2mol/L and 2.5mol/L.
According to an embodiment of the invention, the counter-current extraction has an equilibration time of 0-30min, exemplary 5min, 10min, 15min, 20min, 25min, 30min.
According to an embodiment of the invention, the ratio O/A at the time of the countercurrent extraction is 1/2 to 4/1, and is exemplified by 1/2, 1/3, and 1/4.
According to an embodiment of the invention, the countercurrent extraction is a multistage countercurrent extraction, such as two, three, four, preferably three.
According to the embodiment of the invention, the high-temperature calcination temperature is 800-1000 ℃, and is 800 ℃, 900 ℃ and 1000 ℃ in an exemplary manner, and the calcination time is 2-4 h, and is 2h, 3h and 4h in an exemplary manner.
The invention also provides the rare earth oxide obtained by separation and preparation by the method.
The invention also provides application of the rare earth oxide obtained by separation by the method in the fields of fluorescence, magnetism, optics, catalysis and the like.
The invention has the beneficial effects that:
(1) The invention provides that HDESs based on trioctylphosphine oxide (TOPO) as a Hydrogen Bond Acceptor (HBA), decyl Alcohol (DA), dodecyl alcohol (LA) and tetradecyl alcohol (MA) as Hydrogen Bond Donors (HBD) is firstly applied to separating and recycling REEs from waste neodymium iron boron permanent magnet leaching liquid. According to the invention, HDESs can recover 99% of rare earth in the waste neodymium iron boron permanent magnet leaching solution in the presence of high-concentration iron ions, and the purity of the recovered rare earth oxide mixture is greater than 99%, so that the complete separation of rare earth and iron can be realized. And compared with the traditional solvent extraction, the method does not need to use volatile solvent (kerosene), and is green and clean. In addition, the traditional process needs to remove iron firstly and then uses traditional solvent extraction to recycle rare earth.
(2) The present invention comprehensively evaluates all physicochemical properties of HDESs based on TOPO as HBA, decyl Alcohol (DA), dodecyl alcohol (LA), tetradecyl alcohol (MA) as HBD. The best HDES (DA: MA: topo=5:5:4) was screened by comparing the extractive separation performance of the different HDESs under the same conditions. The invention researches the influence factors (such as nitric acid concentration, iron ion concentration, reaction time, comparison and the like) of the HDES extraction separation performance under a nitric acid system. And evaluate the peeling and regenerating properties of HDES. Under the optimal condition, a new process for recycling the waste neodymium-iron-boron permanent magnet is designed and a batch countercurrent extraction experiment is carried out. The process of the invention does not need to consume acid, alkali or salt and other chemicals in addition to a small amount of nitric acid used in leaching and sodium oxalate used in back extraction.
(3) The invention provides a brand new process for recycling rare earth in waste neodymium iron boron permanent magnet nitric acid leaching solution based on HDES, which prepares and characterizes 13 HDESs, wherein the low viscosity (< 50 mPa.s), the low water solubility (< 100 mg/L), the low water content (< 3%) and the large density difference (about 0.15g/cm -3) with water all make the process become an extracting agent with potential. Through a series of screening work, the novel ternary HDES (for example DA: MA: TOPO=5:5:4) has the best extraction separation performance in the leaching liquid of the waste NdFeB nitric acid system, and an ion association mechanism is provided by optimizing extraction conditions (nitric acid concentration, iron ion concentration and reaction time) and combining infrared spectrum analysis. Ternary HDES (e.g., DA: MA: topo=5:5:4) still has good stability after five cycles. Comparing solvent extraction with HDES extraction, HDES has better extraction separation performance, and the load is far greater than that of solvent extraction. Under the optimal condition, HDES is adopted to carry out three-stage countercurrent extraction with the ratio (O/A) of 2 and the actual leaching solution, rare earth residue (0.1%) is almost absent in the raffinate, and the loaded organic phase can realize the stripping and separation of rare earth and a small amount of iron in the loaded organic phase through 0.2mol/L sodium oxalate. Ternary HDES (e.g., DA: MA: topo=5:5:4) still has good stability after five cycles. The process does not need salting-out agent and toxic volatile solvent, and is favorable for safe and clean production.
Drawings
Fig. 1 is a structural formula of hydrogen bond acceptors (TOPO) and hydrogen bond donors (DA, LA, MA).
In FIG. 2, (a), (b) and (c) are respectively the hydrogen spectra of DA: TOPO (2:1) HDES, the comparison of DA: TOPO (2:1) HDES with the infrared spectra of its precursors, and the electrostatic potential diagrams of hydrogen bond acceptors (TOPO) and hydrogen bond donors (DA, LA, MA) on Van der Waals surfaces.
Fig. 3 (a) and (b) are graphs showing the results of comparison of the effect of HDES of five different combinations of hydrogen bond donors on extraction rate and the three HDES separation coefficients of iron and rare earth, respectively.
FIG. 4 shows the effect of DA: MA: TOPO on extraction in different molar ratios in ternary HDES.
Fig. 5 (a) and (b) are graphs showing the effect of the concentration of the salting-out agent (NaNO 3) on the extraction rate and the infrared spectrogram comparison result of HDES of the rare earth (Dy, nd, pr) and the rare earth (Dy, nd, pr) under load.
In FIG. 6, (a), (b) and (c) are graphs showing the results of the effects of nitric acid concentration, ferric ion concentration and reaction time on the extraction rate, respectively.
In FIG. 7, (a), (b) and (c) are respectively graphs showing the effect of the concentrations of three stripping agents (HNO 3,HCl,Na2C2O4) on the stripping rate, graphs showing the effect of the regeneration performance of DA: MA: TOPO (5:5:4) HDES for five cycles on the extraction rate, and graphs showing the comparison of the infrared spectra of DA: MA: TOPO (5:5:4) HDES before and after five cycles.
Fig. 8 (a) and (b) are graphs showing the comparison of TOPO capacity at HDES and kerosene load Pr, respectively, and a comparison of single load extraction rate based on actual leachate.
Fig. 9 (a) and (b) are graphs showing the results of the comparative effect on the extraction rate, respectively, on the microphone cloth Wei Tu for the countercurrent extraction of rare earth.
Fig. 10 is a process flow diagram for recovering rare earth from NdFeB magnet leaching solution.
Detailed Description
The technical scheme of the invention will be further described in detail below with reference to specific embodiments. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the invention. All techniques implemented based on the above description of the invention are intended to be included within the scope of the invention.
Unless otherwise indicated, the starting materials and reagents used in the following examples were either commercially available or may be prepared by known methods.
Example 1
1. Experimental part
1.1 Reagents and materials
In the following examples of the present invention, the composition of Dy (NO 3)3·6H2 O (99.99%,),Nd(NO3)3·6H2O(99.99%,),Pr(NO3)3·6H2O(99.99%,),Fe(NO3)3·9H2O(99.99%,),Co(NO3)2·6H2O(99.99%,) Dissolved in deionized water to prepare a simulated feed solution for pre-screening HDES and optimizing extraction process conditions, HNO 3 can be used to adjust the acidity of the solution. NaNO 3 can be used to adjust the concentration of salting-out agent. In addition to HNO 3, the stripping agent choices include HCl (36-38%, hirude reagent) and Na 2C2O4 (99%). Precursor materials for use in preparing HDES include trioctylphosphane oxide (TOPO) (98%, macklin), decanol (DA) (97%,) Dodecanol (LA) (99%, adamas-beta)) Myristyl Alcohol (MA) (98%,). For comparison of solvent extraction, conventional solvent sulfonated kerosene (Shanghai rare earth chemical Co., ltd.) was also selected.
1.2 Instruments and analytical methods
The concentration of metal ions in the water sample was determined by inductively coupled plasma atomic emission spectrometry (ICP-OES, jy-Horiba ICP-OES Ultima 2), the density, viscosity, water content of HDES and solubility of HDES in the aqueous phase were determined by Biolin automated surface tensiometer Sigma 701 (density accuracy ± 0.001g x cm -3), viscosity by rotary viscometer (NDJ-5, shanghai, china, accuracy ± 2%), metrohm 831kf coulometer (accuracy ± 0.01 wt%), and total organic carbon analysis (TOC, shimadzu TOC-L CPH analyzer), respectively, the concentration of the element loaded in the HDES organic phase was calculated by mass conservation law. The acidity of the sample can be obtained by inverse calculation by measuring the acidity by a digital pH meter of pHS-3C (accuracy.+ -. 0.01) manufactured by Shanghai Raney instruments factory after dilution by a weighing method. The purity of the final rare earth product is determined by EDS. HDES A 1 H NMR spectrum was determined by means of an AV III-500Bruker spectrometer using CDCl 3 as solvent. Fourier transform infrared spectra (FT-IR) of HDES before and after extraction were measured by Thermo Nicolet IS instrument, with wavenumbers in the range 400-4000cm -1.
1.3 Calculation method
The initial structure of HBDs and HBAs was constructed by the GaussView 5.0 procedure. Quantum stoichiometry was performed by a Gaussian 09 program. Van der Waals half-empirical contribution of the density functional theory calculation (DFT) at the B3LYP/6-311G (D, p) level plus the Grimme DFT-D3 (BJ) method is used to optimize stable configurations. The optimized structure is then frequency calculated on the same method and basis to confirm that no virtual frequencies are present. The multiwfn3.8 program was used in conjunction with the VMD1.9.3 program to perform electrostatic potential (ESP) analysis and mapping.
1.4HDES preparation
Physical and chemical properties of the Hydrogen Bond Acceptor (HBA) and Hydrogen Bond Donor (HBD) components selected in the invention are shown in Table 2, and all HDES are prepared by mixing HBA and HBD according to a given molar ratio, placing the mixture in a glass bottle, and heating the mixture at 60 ℃ for 15 min. Physical properties of HDES prepared are shown in table 2. All HDESs remained colorless and transparent after 48 hours of standing at room temperature (25 ℃ C..+ -. 2), and had a good fluidity.
1.5 Extraction and stripping experiments
All extraction experiments are carried out at room temperature, the initial acidity of the feeding simulation solution is 1mol/L, elements contained in the simulation feed liquid comprise Nd, dy, pr, fe and Co, the initial concentration is 0.01mol/L, the ratio of HDES to the water phase is 1:1, and in order to ensure full reaction, the extraction process is carried out by shaking for 30min at a vibration speed of 300 rpm. After extraction, the elemental concentration in the raffinate was determined by ICP-OES.
The influence of the initial acidity (0.5-2.5 mol/L) of the feed liquid, the balance time (0-30 min), the iron ion concentration (0.01-0.21 mol/L) and the like on the rare earth extraction performance and the rare earth and iron separation performance of HDES compared with the influence of the O/A (1/2-4/1) and the like is examined.
Three different stripping agents (HNO 3,HCl,Na2C2O4) were used to carry out stripping experiments on the loaded HDES (loading conditions: nitric acid concentration of 1mol/L in solution, dy 3+,Nd3+,Pr3+,Fe3+,Co2+ ion concentration of 0.01mol/L in comparison to 1:1, reaction time of 15 min), the non-stripped rare earth elements in the organic phase were completely stripped by strong acid in comparison to 1:1, and the residual ion concentration of the stripping solution was determined by ICP-OES. The maximum load of HDES was calculated by conservation law of the material by measuring the raffinate obtained each time by repeating the contact reaction 5 times with the same HDES times using 5 times fresh feed. The mechanism of extracting rare earth in a nitric acid system by HDES is presumed through infrared and salting-out agent experiments.
1.6 Leaching and recovery of NdFeB waste
The NdFeB (NdFeB) scrap selected in the invention is purchased from Alibaba Hebei beyond metal products limited. The complete leaching is achieved by using 3mol/L nitric acid under the conditions of S/L=0.02 g/L and 80 ℃ oil bath constant temperature heating for 2 hours, and no solid residue exists after the reaction is finished. The main components and concentrations of the actual feed liquid after complete leaching are shown in table 1 below. Under the optimal experimental conditions (nitric acid concentration is 2.21mol/L, compared with 2:1, the reaction time is 15min, the temperature is room temperature (25 ℃), and the three-stage countercurrent extraction is performed), the established HDES is selected for batch countercurrent extraction experiments. Carrying out HDES of back extraction on rare earth element loaded rare earth element by using sodium oxalate, washing and drying rare earth oxalate precipitate, and then roasting for 3 hours at 800 ℃ in a muffle furnace to prepare rare earth oxide.
TABLE 1 principal Components and concentration of actual feed liquid after complete leaching of NdFeB
2. Results and discussion
2.1 Characterization 2.1HDESs
Because phenol is relatively toxic and water-soluble, it is a major trend to find low-toxicity, low-water-solubility Hydrogen Bond Donors (HBD) and trioctyl phosphorus oxide (TOPO) to prepare eutectic solvents. The invention selects Decyl Alcohol (DA), dodecyl alcohol (LA) and tetradecyl alcohol (MA) as Hydrogen Bond Donors (HBD) and hydrogen bond acceptors (TOPO) to prepare eutectic solvents (DESs) for selectively recovering rare earth elements in a nitric acid system. The invention prepares 13 DESs altogether, the chemical structures of selected materials (hydrogen bond acceptors (TOPO) and hydrogen bond donors (DA, LA, MA)) are shown in figure 1, the physical and chemical properties of the materials are summarized in the attached table 2, and the selected materials mainly have the advantages of almost negligible water solubility, non-volatility, relatively low-cost pure components, stable physical and chemical properties, environmental friendliness and the like.
The HDESs prepared by the method can keep a uniform and transparent liquid state after being stored for 48 hours at room temperature. We take HDES for the composition DA: TOPO (molar ratio of 2:1) as an example, it can be seen that the 1 H NMR (fig. 2 (a)) and FT-IR (fig. 2 (b)) analyses of HDES did not show any new peaks compared to the two original components, indicating that no chemical reaction between Decanol (DA) and TOPO occurred. As can be seen by FT-IR analysis, the P=O stretching vibration peak in HDES is at 1139.72cm -1, and compared with the P=O stretching vibration peak (1144.06 cm-1) of pure TOPO, the P=O stretching vibration peak is obviously shifted to low frequency, and the change indicates that hydrogen bonding exists between the P=O stretching vibration peak and the P=O stretching vibration peak.
Electrostatic potential (ESP) is an important tool for identifying interaction sites and hydrogen bonding interactions. As is apparent from fig. 2 (c), the oxygen (O) atom at the p=o double bond position of TOPO exhibits the most negative potential (shown as red region). In contrast, the hydrogen (H) atoms in the-OH groups of the linear alcohols DA, LA and MA show the most positive potential (shown as blue region). Thus, TOPO and linear alcohols are expected to form intermolecular hydrogen bonds in the region of maximum/minimum potential under the drive of electrostatic attraction. As described above, these findings further support the results obtained from infrared spectroscopy, thereby confirming the presence of hydrogen bond interactions between TOPO and linear alcohols.
Good physicochemical properties are the conditions that must be possessed by an extractant with excellent performance, for which we have determined the main physicochemical properties of HDESs produced (including water content, organic carbon content in the aqueous phase, viscosity, density, etc.). As can be seen from Table 2, even after HDESs prepared under 1:1 conditions was fully contacted with deionized water for 24 hours. HDESs still has water content lower than 3%, and the organic carbon content in the water phase is lower than 100mg/L. Therefore, HDESs prepared by the method has good hydrophobicity and environmental friendliness.
Considering that the leaching of spent neodymium iron boron magnets requires the use of strong acid leaching, we have to evaluate HDES's stability under acidic conditions. Taking LA: TOPO (molar ratio of 2:1) as an example, after HDES is balanced with 3mol/L nitric acid, no new peak appears in 1 H NMR spectrum, which shows that the HDES has good stability under the condition of strong acid. It can also be seen from the FT-IR spectrum that the p=o stretching vibrational peak shifts to low frequencies, possibly due to its HDES protonation. In the liquid-liquid extraction process, the low viscosity of the organic phase is beneficial to improving the mass transfer rate and the extraction efficiency, and the problems of difficult phase separation and the like are avoided. The HDESs prepared by the invention has the viscosity of less than 40 mPas at room temperature, which is far lower than most reported ionic liquids with high hydrophobicity. Thus, no toxic volatile organic solvents need be added during the extraction process. In addition, the density of HDESs prepared by the method is about 0.85, and the density of HDESs is greatly different from that of water phase, so that HDESs is better separated from water after liquid-liquid extraction.
TABLE 2 physicochemical Properties of HDESs at 25.+ -. 2 ℃
2.2HDESs screening
According to the invention, firstly, the extraction and separation performance of HDESs kinds of HBDs and HBAs (TOPO) prepared by 5 different combinations according to the mol ratio of 1:1 in the waste neodymium-iron-magnet simulated feed liquid is evaluated. As can be seen from FIG. 3 (a), the rare earth extraction rates of DA, LA, DA, MA, and HDES are almost equivalent to those of HBA (TOPO), while the rare earth extraction rate of HDES prepared from LA, MA (molar ratio 1:1) and HBA (TOPO) is greatly reduced, while HDES prepared from MA and HBA (TOPO) has almost no extraction performance in the system, so HDESs prepared from LA, MA, HBD and HBA (TOPO) is first excluded. In terms of iron extraction performance, DA: MA < LA < DA, thus rendering HDES prepared from DA: MA and HBA (TOPO) far greater in separation performance than the other two. This is probably because the hydrogen bonding action to which TOPO as a hydrogen bonding acceptor is subjected gradually increases, resulting in that HDESs performance of extracting iron is inhibited, and thus the separation coefficient of rare earth and iron is improved. The final choice was therefore to prepare HDES with DA and MA together as HBD and TOPO as HBA for subsequent experiments.
We prepared different HDES by varying the molar ratio between DA, MA and TOPO and studied the effect of each component on its performance by comparing the extractive separation performance of different HDES under the same conditions, the results are shown in FIG. 4. As can be seen from fig. 4, in the case of a fixed TOPO molar amount, when the molar ratio of DA to MA is 1 or less, the rare earth extraction rate is not significantly changed, while the extraction rate of iron is gradually reduced to 0, and when the molar ratio of DA to MA to TOPO is 3:7:5, the rare earth extraction rate is greatly reduced. This is probably due to the fact that MA hydrogen bonding forces to TOPO in HDES are much greater than DA hydrogen bonding forces to TOPO. In addition, with a fixed molar ratio of DA to MA, the extraction rate of rare earth to iron overall tends to increase with increasing mole fraction of TOPO, probably because TOPO, a component in HDES, plays a major role in the extraction process. Finally, HDES prepared from DA: MA: TOPO according to a molar ratio of 5:5:4 is preferable as an extractant from the viewpoint of combining rare earth extraction performance and impurity separation performance.
2.3 Investigation of extraction mechanism
In order to explore the extraction mechanism of HDES in an extraction system so as to better regulate and control the extraction process to achieve the optimal extraction effect. In order to avoid the mutual influence between elements, we use a single element solution (the solution composition is that single element (rare earth element Dy, nd or Pr), the concentration of rare earth element is 0.1mol/L, the concentration (acidity) of hydrogen ion is 1 mol/L.) to observe the influence of salting-out agent (changing the concentration of nitrate anion by adding sodium nitrate, compared with 1:1, the reaction time is 20 min.) on the extraction process, and it can be found from FIG. 5 (a) that as the concentration of NaNO 3 in the solution increases from 0 to 0.7mol/L, the extraction rate of all rare earth elements increases from about 30% to 75%, the reaction proceeds forward, which indicates that NO 3 - anion participates in the reaction. FIG. 5 (b) is a graph showing the characteristics of infrared spectra before and after HDES supporting rare earth (Dy, nd, pr), wherein 2918-2924cm -1、2847-2858cm-1、1460-1466cm-1 are respectively asymmetric stretching vibration, symmetric stretching vibration and shearing vibration peaks of TOPO alkyl chain, and P=O stretching vibration peaks of TOPO are near 1144-1150cm -1. Meanwhile, the tensile vibration peak of P=O of HDES after rare earth ions are loaded is moved from 1140cm -1 to 1122cm -1 or so, which shows that TOPO is dominant in the extraction process in HDES and has interaction with rare earth ions. Meanwhile, the electronegativity of the O atom is larger than that of the P atom, so that the electron cloud of the double bond of P=O is biased to the O atom, but the lone pair electron of the O atom can form a complex with the rare earth ion, so that the electron cloud changes, and the stretching vibration peak of P=O is further promoted to be red shifted. In summary, the extraction mechanism of HDES in the system of the present invention is presumed to be an ion association mechanism, and the equation is:
2.4 optimization of extraction conditions
In order to further improve the extraction separation performance of HDES, the influence of parameters such as nitric acid concentration, reaction time, iron ion concentration and the like on the extraction rate (Dy 3+,Nd3+,Pr3+,Fe3+,Co2+ is contained in simulated feed liquid, the initial ion concentration is 0.01mol/L, compared with 1:1, the reaction time is 15min. In the influence experiment of nitric acid concentration on the extraction rate, the nitric acid concentration is changed from 0.5mol/L to 2.5mol/L through fixing other conditions, the reaction time is changed from 1min to 25min through fixing other conditions in the influence experiment of the reaction time on the extraction rate, and the iron ion concentration is changed from 0.01mol/L to 0.21mol/L through fixing other conditions in the influence experiment of the iron ion concentration on the extraction rate) is examined. The experimental results are shown in fig. 6 (a), (b) and (c).
In FIG. 6 (a), it is shown that the extraction ratio of rare earth and iron tends to decrease as the nitric acid concentration increases from 0.5mol/L to 2.5 mol/L. This is probably because, at high acidity, hydrogen ions compete with rare earth ions, and as the concentration of nitric acid increases, the competition ability of hydrogen ions increases, resulting in a decrease in the extraction rate of rare earth and iron.
In addition, FIG. 6 (c) shows that after the reaction time reaches 10min, the extraction rate of rare earth does not change significantly, indicating that the kinetic equilibrium of rare earth extraction has been reached. However, when the reaction time is further prolonged to 25min, the extraction rate of iron still tends to increase, which indicates that the extraction kinetics of rare earth is faster relative to the extraction kinetics of iron, so that the separation performance of rare earth and iron can be further improved by properly adjusting the reaction time.
Considering that the concentration of iron ions in the actual feed liquid is higher, the influence of the iron ions on the extraction separation performance is researched by improving the concentration of the iron ions. As can be seen from FIG. 6 (b), as the iron ion concentration increases from 0.01mol/L to 0.21mol/L, the rare earth extraction rate overall increases, which is probably due to the fact that nitrate participates in coordination, and the reaction proceeds forward due to the increase in nitrate concentration in the feed solution, and the extraction rate increases. The extraction rate of iron is also increased from 0.09% to 3.11%, and the iron loading in the organic phase is also increased from 0.0005g/L to 0.3647g/L. This is mainly due to homoionic effects.
2.5HDES stripping and regeneration
Simple, green, clean stripping and reuse are important metrics for HDES as extractant. Three stripping agents (HCl, HNO 3 and Na 2C2O4) are selected for the stripping regeneration experiment. It can be found from fig. 7 (a) that the stripping effect of hydrochloric acid is superior to that of nitric acid under the same conditions, probably because chloride ions of hydrochloric acid do not participate in the extraction reaction, do not affect the progress of the reaction, and nitrate ions of nitric acid participate in the coordination, resulting in poor stripping effect. Although 5mol/L hydrochloric acid can realize complete back extraction of rare earth, in consideration of factors such as excessive back extraction acidity and possible incapability of stripping small amount of loaded iron elements in HDES in subsequent actual feed liquid, sodium oxalate (Na 2C2O4) is selected for back extraction experiments. This is because sodium oxalate can separate rare earth as a precipitate, while iron oxalate exists as a solution, which is advantageous for further separation of rare earth and iron elements and for improvement of purity of the final product. As can be seen from FIG. 7 (a), the complete stripping of HDES can be achieved with 0.2mol/L sodium oxalate.
After complete back extraction, HDES of washing with deionized water for several times can be used for the next round. In order to better embody the circulating performance of HDES, the actual leaching solution is used as circulating feed liquid. As can be seen from FIG. 7 (b), the extraction yield of HDES of the present invention remained substantially unchanged in five cycles, showing higher stability. By infrared spectroscopy, we can also see that there is substantially no change in structure between before and after HDES cycles. Therefore, HDES of the invention has better back extraction regeneration and reutilization performance.
2.6HDES comparison with solvent extraction
The highest concentration of TOPO in kerosene was reported to be 0.5mol/L. However, the concentration of TOPO in HDES can be as high as about 1mol/L, much higher than in kerosene, due to the hydrogen bonding interactions present in HDES. The invention takes the rare earth element Pr which is the most difficult to extract in the NdFeB permanent magnet as an example, and compares the loading capacities of HDES and solvent extraction. Although the concentration of TOPO in HDES is much higher than that in kerosene, the loadings of the rare earth element Pr are almost similar, and we speculate that it is possible that some TOPO cannot participate in the reaction because of the relatively strong force of HBD (mixed alcohol DA: MA, molar ratio 5: 5) on TOPO. In order to better reflect the difference between TOPO in HDES and kerosene solvent, we compare the actual leaching solution as mother liquor, and it can be seen from FIG. 8 (b) that the extraction capacity of HDES to rare earth is better than that of TOPO in kerosene, and meanwhile, compared with TOPO which can Co-extract a small amount of impurity elements in kerosene (the extraction rate of Fe is 4.38% and the extraction rate of Co is 0.61%), HDES can achieve that other impurity elements such as Fe, co and the like are not extracted under the condition, thereby realizing the complete separation of rare earth and impurity elements. Meanwhile HDES does not need to use volatile toxic solvents, and provides a new idea for green clean production.
2.7 New process for recovering rare earth from actual feed liquid
To investigate the effect of the phase ratio on the separation and extraction performance of HDES, we performed a series of experiments (simulating that the elements contained in the feed liquid have Dy 3+,Nd3+,Pr3+,Fe3+,Co2+, the initial ion concentration is 0.01mol/L, the phase ratio is 1:1, and the reaction time is 15min. By fixing other conditions, the phase ratio (O/A) is changed from 1:2 to 4:1.) and plotted the relationship between the phase ratio and the rare earth extraction rate. It can be seen from fig. 9 (a) that the HDES system significantly improves the extraction efficiency for rare earth when the ratio is increased from 1:2 to 4:1, probably because the probability of the TOPO molecules acting in HDES and the rare earth ions in solution contacting each other to collide increases with the increase in the ratio. At the same time, as the phase ratio increases, the extraction rate of the impurity element iron also increases, but the extraction rate of iron tends to stabilize after the phase ratio reaches 4:1, which indicates that HDES may already be saturated with iron. In order to realize complete recovery of rare earth in the waste NdFeB magnet leaching solution, multistage countercurrent extraction is needed, and parameters are optimized by utilizing MaCabe-Thiele diagram. We select a 2:1 ratio and plot the slope of the line in the graph at 1/2 to estimate the number of stages required to extract rare earth. As can be seen from the results of fig. 9 (b), three extraction stages are required to achieve complete extraction and separation of rare earth elements. Therefore, under the optimal experimental conditions, a new process for recycling rare earth in NdFeB waste leaching solution is developed, and batch countercurrent extraction experiments are carried out.
Firstly, adopting HDES to extract rare earth elements from a feed solution selectively by three-stage countercurrent extraction with the ratio (O/A) of 2:1, stripping and regenerating HDES organic phase loaded with rare earth by using 0.2mol/L sodium oxalate, washing the organic phase, then entering the circulation, and roasting rare earth oxalate products after washing and drying to obtain rare earth products. The detailed parameters of the countercurrent extraction experiment are shown in Table 3. The total rare earth ion concentration in the mother liquor is reduced from 4325.7mg/L to 32.32mg/L through three-stage countercurrent extraction, the rare earth recovery rate reaches more than 99%, and the iron loaded in the organic phase is about 266mg/L, but a small amount of iron loaded in the organic phase can be further completely separated from rare earth through sodium oxalate back extraction.
TABLE 3 results of countercurrent extraction experiments
In summary, the invention provides a brand new process for recycling rare earth in the nitric acid leaching solution of the waste neodymium iron boron permanent magnet based on HDES, which totally prepares and characterizes 13 HDESs, and is an extractant with potential based on low viscosity (< 50 mPa.s), low water solubility (< 100 mg/L), low water content (< 3%) and large density difference with water (about 0.15g/cm -3). Through a series of screening work, the novel ternary HDES (DA: MA: TOPO=5:5:4) has optimal extraction and separation performance in the leaching liquid of the waste NdFeB nitric acid system, and an ion association mechanism is provided by researching and optimizing extraction conditions (nitric acid concentration, iron ion concentration and reaction time) and combining infrared spectrum analysis. Ternary HDES (DA: MA: topo=5:5:4) still had better stability after five cycles. Meanwhile, compared with solvent extraction and HDES extraction, the invention finds that HDES has better extraction and separation performance, and the load capacity is far greater than that of solvent extraction. Under the optimal condition, HDES is adopted to carry out three-stage countercurrent extraction with the ratio (O/A) of 2 and the actual leaching solution, rare earth residues are almost absent in the raffinate (the rare earth residue is as low as 0.1 percent), and the loaded organic phase can realize the stripping and separation of rare earth and a small amount of iron in the loaded organic phase through 0.2mol/L sodium oxalate. Ternary HDES (DA: MA: topo=5:5:4) still had better stability after five cycles. The process does not need salting-out agent and toxic volatile solvent, and is favorable for safe and clean production.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
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