CN116478061A - Extractant for separating thorium and recycling rare earth elements as well as preparation method and application thereof - Google Patents
Extractant for separating thorium and recycling rare earth elements as well as preparation method and application thereof Download PDFInfo
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- CN116478061A CN116478061A CN202210038597.3A CN202210038597A CN116478061A CN 116478061 A CN116478061 A CN 116478061A CN 202210038597 A CN202210038597 A CN 202210038597A CN 116478061 A CN116478061 A CN 116478061A
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 102
- 229910052776 Thorium Inorganic materials 0.000 title claims abstract description 55
- ZSLUVFAKFWKJRC-IGMARMGPSA-N 232Th Chemical compound [232Th] ZSLUVFAKFWKJRC-IGMARMGPSA-N 0.000 title claims abstract description 54
- 238000002360 preparation method Methods 0.000 title claims abstract description 8
- 238000004064 recycling Methods 0.000 title description 5
- 238000000605 extraction Methods 0.000 claims abstract description 71
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 37
- 238000000034 method Methods 0.000 claims abstract description 21
- 230000008569 process Effects 0.000 claims abstract description 9
- 125000000217 alkyl group Chemical group 0.000 claims abstract description 6
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 claims description 66
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 58
- 239000007788 liquid Substances 0.000 claims description 39
- 239000012074 organic phase Substances 0.000 claims description 32
- 235000006408 oxalic acid Nutrition 0.000 claims description 22
- 238000000926 separation method Methods 0.000 claims description 21
- 238000005406 washing Methods 0.000 claims description 21
- 239000002699 waste material Substances 0.000 claims description 18
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 17
- PHMNXPYGVPEQSJ-UHFFFAOYSA-N Dimethoxane Chemical compound CC1CC(OC(C)=O)OC(C)O1 PHMNXPYGVPEQSJ-UHFFFAOYSA-N 0.000 claims description 12
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 claims description 12
- 150000001875 compounds Chemical class 0.000 claims description 12
- 239000002994 raw material Substances 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 239000002253 acid Substances 0.000 claims description 10
- -1 oxalyl chloride monoethyl ester Chemical class 0.000 claims description 10
- 239000013067 intermediate product Substances 0.000 claims description 8
- 150000007524 organic acids Chemical class 0.000 claims description 8
- 239000008346 aqueous phase Substances 0.000 claims description 7
- 238000002386 leaching Methods 0.000 claims description 7
- IMNFDUFMRHMDMM-UHFFFAOYSA-N N-Heptane Chemical compound CCCCCCC IMNFDUFMRHMDMM-UHFFFAOYSA-N 0.000 claims description 6
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 6
- 239000003085 diluting agent Substances 0.000 claims description 6
- 238000011068 loading method Methods 0.000 claims description 6
- 150000007522 mineralic acids Chemical class 0.000 claims description 6
- 238000002156 mixing Methods 0.000 claims description 6
- CTSLXHKWHWQRSH-UHFFFAOYSA-N oxalyl chloride Substances ClC(=O)C(Cl)=O CTSLXHKWHWQRSH-UHFFFAOYSA-N 0.000 claims description 6
- 150000007529 inorganic bases Chemical class 0.000 claims description 5
- 239000012527 feed solution Substances 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 4
- 239000003350 kerosene Substances 0.000 claims description 4
- GMTCPFCMAHMEMT-UHFFFAOYSA-N n-decyldecan-1-amine Chemical compound CCCCCCCCCCNCCCCCCCCCC GMTCPFCMAHMEMT-UHFFFAOYSA-N 0.000 claims description 4
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 claims description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- 229910001424 calcium ion Inorganic materials 0.000 claims description 3
- 229910017604 nitric acid Inorganic materials 0.000 claims description 3
- 238000001354 calcination Methods 0.000 claims description 2
- 229910052500 inorganic mineral Inorganic materials 0.000 claims description 2
- 229910052746 lanthanum Inorganic materials 0.000 claims description 2
- 239000011707 mineral Substances 0.000 claims description 2
- 229910052727 yttrium Inorganic materials 0.000 claims description 2
- 239000000284 extract Substances 0.000 abstract description 6
- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 25
- 239000000243 solution Substances 0.000 description 10
- 238000012360 testing method Methods 0.000 description 9
- 230000000694 effects Effects 0.000 description 8
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 description 6
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical group [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 239000011575 calcium Substances 0.000 description 5
- 239000012071 phase Substances 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- SOWBFZRMHSNYGE-UHFFFAOYSA-N oxamic acid Chemical compound NC(=O)C(O)=O SOWBFZRMHSNYGE-UHFFFAOYSA-N 0.000 description 4
- 239000002893 slag Substances 0.000 description 4
- STCOOQWBFONSKY-UHFFFAOYSA-N tributyl phosphate Chemical compound CCCCOP(=O)(OCCCC)OCCCC STCOOQWBFONSKY-UHFFFAOYSA-N 0.000 description 4
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 description 3
- 239000003795 chemical substances by application Substances 0.000 description 3
- 238000000151 deposition Methods 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 239000000047 product Substances 0.000 description 3
- 230000002285 radioactive effect Effects 0.000 description 3
- 239000002901 radioactive waste Substances 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000002351 wastewater Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- ABLZXFCXXLZCGV-UHFFFAOYSA-N Phosphorous acid Chemical compound OP(O)=O ABLZXFCXXLZCGV-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000007795 chemical reaction product Substances 0.000 description 2
- 239000008367 deionised water Substances 0.000 description 2
- 229910021641 deionized water Inorganic materials 0.000 description 2
- 238000002474 experimental method Methods 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000001644 13C nuclear magnetic resonance spectroscopy Methods 0.000 description 1
- 238000005160 1H NMR spectroscopy Methods 0.000 description 1
- LJKDOMVGKKPJBH-UHFFFAOYSA-N 2-ethylhexyl dihydrogen phosphate Chemical compound CCCCC(CC)COP(O)(O)=O LJKDOMVGKKPJBH-UHFFFAOYSA-N 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 229910052765 Lutetium Inorganic materials 0.000 description 1
- 238000003916 acid precipitation Methods 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 125000002704 decyl group Chemical group [H]C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])C([H])([H])* 0.000 description 1
- SEGLCEQVOFDUPX-UHFFFAOYSA-N di-(2-ethylhexyl)phosphoric acid Chemical compound CCCCC(CC)COP(O)(=O)OCC(CC)CCCC SEGLCEQVOFDUPX-UHFFFAOYSA-N 0.000 description 1
- 239000000539 dimer Substances 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 238000004945 emulsification Methods 0.000 description 1
- 239000003344 environmental pollutant Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 238000005194 fractionation Methods 0.000 description 1
- 238000009854 hydrometallurgy Methods 0.000 description 1
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 1
- 239000005457 ice water Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910017053 inorganic salt Inorganic materials 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 239000011259 mixed solution Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 230000020477 pH reduction Effects 0.000 description 1
- 238000005191 phase separation Methods 0.000 description 1
- 239000002798 polar solvent Substances 0.000 description 1
- 231100000719 pollutant Toxicity 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 125000002924 primary amino group Chemical class [H]N([H])* 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 238000003904 radioactive pollution Methods 0.000 description 1
- 238000010992 reflux Methods 0.000 description 1
- 238000007127 saponification reaction Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000000638 solvent extraction Methods 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000003911 water pollution Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C233/00—Carboxylic acid amides
- C07C233/01—Carboxylic acid amides having carbon atoms of carboxamide groups bound to hydrogen atoms or to acyclic carbon atoms
- C07C233/56—Carboxylic acid amides having carbon atoms of carboxamide groups bound to hydrogen atoms or to acyclic carbon atoms having carbon atoms of carboxamide groups bound to carbon atoms of carboxyl groups, e.g. oxamides
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C231/00—Preparation of carboxylic acid amides
- C07C231/02—Preparation of carboxylic acid amides from carboxylic acids or from esters, anhydrides, or halides thereof by reaction with ammonia or amines
-
- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
- C07C231/00—Preparation of carboxylic acid amides
- C07C231/12—Preparation of carboxylic acid amides by reactions not involving the formation of carboxamide groups
-
- 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
-
- 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
Landscapes
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Engineering & Computer Science (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Life Sciences & Earth Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Manufacture And Refinement Of Metals (AREA)
- Extraction Or Liquid Replacement (AREA)
Abstract
The invention discloses an extractant, a preparation method and application thereof, wherein the extractant has a structure shown in the following formula 1, R can be the same or different and are independently selected from C 10‑20 An alkyl group. The extractant can effectively separate rare earth metals from thorium by less cascade stages, reduces the use amount of the extractant, solves the problem of difficult back extraction after the extractant extracts thorium, and reduces the process difficulty.
Description
Technical Field
The invention relates to the technical field of rare earth separation, in particular to an extractant for treating rare earth waste residues and recycling thorium and rare earth elements, and a preparation method and application thereof.
Background
In the rare earth separation industry, most of thorium is transferred to rare earth waste residues, causing radioactive pollution. The treatment of radioactive waste residues with high contents of rare earth elements (denoted as REEs or REEs) is a significant challenge facing the Rare Earth (RE) industry. Because radioactive elements can pollute the environment along with rainwater migration, the treatment of the rare earth radioactive waste residues has important significance, is beneficial to recycling rare earth and radioactive elements, and reduces the volume of solid pollutants.
In the field of solvent extraction, many extractants have been investigated for thorium (Th) removal. Under mild conditions, th extraction and stripping at low cost and with little contamination is an important issue. It is difficult to simultaneously achieve efficient extraction and stripping separation using one extractant. Tributyl phosphate (TBP) is a commonly used extractant for the separation of lithium, thorium and rare earths. In Th separation, TBP is required to extract Th at a higher acidity and to perform back extraction under severe conditions. Di (2-ethylhexyl) phosphate (P204) and mono-2-ethylhexyl phosphate (P507) are the two most widely used extractants in hydrometallurgy. Because of their good selectivity, they are widely used in many metal separation industries. In order to reduce the waste water generated during saponification, CN102146512B discloses an extraction system based on non-saponified P204 and P507, which is effective in separating Rare Earth Elements (REEs) and Th, but removal of Th from the organic phase is a great challenge, requiring the addition of high concentrations of acids above 6mol/L during stripping. A primary amine extractant N1923 ((C) has been developed n H 2n+1 ) 2 CHNH 2 N=9-11), the current study aimed at using N1923 to selectively isolate Th in sulfuric or nitric acid medium, but its poor extraction performance in hydrochloric acid medium limited its industrial application. The introduction of N atoms into the organophosphine extractant and redistribution of electrons in the molecule has also been studied, and several extractants have been designed to separate Ce 4+ And Th (Th) 4+ 。
Aiming at the problem that thorium is difficult to strip from rare earth feed liquid, the existing phosphonic acid type extractant is difficult to separate rare earth from thorium, separation can be realized through a plurality of stages, and under the conventional phosphonic acid separation condition, thorium is enriched in an organic phase, the extractant is invalid after a plurality of cascade extractions, and a new extractant is required to be replaced.
In addition, if the back extraction acidity is lower, the acid-base consumption can be reduced, and the generation of wastewater and inorganic salt in the separation process can be reduced. Oxalic acid has become a potential extractant in order to reduce the acidity of the stripping. Oxalic acid has been reported to be used for the separation of light rare earth elements with toluene as a diluent. The oxalic acid obtained by introducing nitrogen atoms into oxalic acid is favorable for improving the extraction performance, however, the oxalic acid is difficult to dissolve in a conventional solvent, the problem of poor oil solubility in extraction and purification of rare earth exists, and the polar solvent used as an oil phase after extraction is seriously lost.
Disclosure of Invention
Aiming at the problem that the existing extractant is difficult to strip, the invention provides an extractant for separating thorium (Th) and Rare Earth Elements (REE) from rare earth waste residues in order to reduce the strip step and the process difficulty. In addition, the extraction agent can extract and separate rare earth elements and thorium in a cascade stage with a small number of stages (such as four-stage extraction, three-stage washing and one-stage back extraction), so that the problem that the extraction agent is difficult to back extract after extracting thorium can be greatly solved, and the extraction agent can be recycled for a plurality of times.
The technical scheme of the invention is as follows:
an extractant having a structure represented by the following formula 1:
wherein R may be the same or different and are independently selected from C 10-20 Alkyl, preferably C 10-16 Alkyl, more preferably C 10-12 Alkyl groups are particularly preferably decyl. That is, the extractant of the present invention is preferably 2- (didecylamino) oxalic acid (DDOA) which is a compound represented by the following formula 2:
according to an embodiment of the invention, the extractant is used to separate thorium (Th) and Rare Earth Elements (REEs).
According to an embodiment of the present invention, the Rare Earth Element (REE) is selected from at least one of La, ce, pr, nd, pm, sm, eu, sc, Y, gd, tb, dy, ho, er, tm, yb, lu.
According to an embodiment of the invention, the loading of the extractant to thorium is 2-3g/L, exemplary 2.81g/L, when the concentration of the extractant is 0.04 mol/L.
According to the embodiment of the invention, the extractant is improved on the basis of the oxamic acid, so that the oil solubility of the extractant can be improved, the water solubility of the extractant is reduced, the water solubility is lower than 110mg/L, the extraction capacity is improved, and the loss of an organic phase is reduced.
According to the embodiment of the invention, the extractant also has good stripping performance, and the stripping rate reaches 98% after three times of stripping under the condition of 3mol/L hydrochloric acid stripping.
According to embodiments of the invention, the extractant of the invention also has good recyclability, and the extraction efficiency of thorium can be maintained at 98% after 5 extraction and stripping cycles.
The invention also provides a preparation method of the extractant, which comprises the following steps:
(1) Mixing and reacting a compound shown in a formula A with oxalyl chloride monoethyl ester to prepare an intermediate product, namely a compound shown in a formula B;
HNR 2 formula A;
wherein R has the meaning as described above;
(2) And (3) reacting the intermediate product in the step (1) with inorganic base, and then acidizing by acid to prepare the extractant.
According to an embodiment of the present invention, in step (1), the temperature of the reaction is 0 to 8 ℃, preferably 0 to 5 ℃.
According to an embodiment of the present invention, in step (1), the molar ratio of the compound represented by formula A to oxalyl chloride monoethyl ester is (0.05-2): 1, exemplary 1:1.
Preferably, the compound of formula a is didecylamine.
According to an embodiment of the present invention, in step (1), a solvent such as methylene chloride, toluene may also be added.
According to an embodiment of the present invention, in step (1), oxalyl chloride monoethyl ester may be added by means of dropwise addition. Illustratively, the rate of addition is 30 drops per minute.
According to the embodiment of the invention, in the step (1), after the reaction is finished, the reaction product can be washed by water, an organic phase is collected, and an organic solvent is removed, namely an intermediate product.
According to an embodiment of the present invention, in step (2), the inorganic base is sodium hydroxide, or potassium hydroxide.
According to an embodiment of the present invention, in step (2), the molar ratio of the compound represented by formula A to the inorganic base is 1 (1-3); preferably 1:2.
According to an embodiment of the invention, in step (2), the acid is hydrochloric acid or sulfuric acid; the concentration of the acid is 4 to 8mol/L, and is exemplified by 6mol/L.
According to an embodiment of the present invention, in step (2), after the acidification is completed, the reaction product is concentrated with methylene chloride, and then the methylene chloride solution is removed to prepare the extractant. For example, the methylene chloride solution is distilled off under reduced pressure.
The invention also provides application of the extractant, which is used for separating thorium and rare earth elements.
The invention also provides a method for recovering thorium and rare earth elements from rare earth waste residues, which comprises the following steps:
(S1) roasting rare earth waste residues, mixing the rare earth waste residues with inorganic acid, and heating and leaching to obtain a raw material liquid containing thorium and rare earth elements;
(S2) extracting the organic phase containing thorium and rare earth elements by adopting a raw material liquid containing the extractant;
(S3) washing the organic phase obtained after the extraction in step (S2) with a washing liquid so that the rare earth element is incorporated into the aqueous phase and thorium remains in the organic phase;
(S4) stripping the organic phase containing thorium obtained in the step (S3) by using a stripping liquid to recover thorium.
According to an embodiment of the present invention, in step (S1), calcium ions, aluminum ions, and the like are further included in the raw material liquid.
According to an embodiment of the invention, the method further comprises the step (S5): adding (NH) to the aqueous phase containing the rare earth element obtained in the step (S3) 4 ) 2 SO 4 After removing calcium sulfate, a residual liquid was obtained.
According to an embodiment of the invention, the method further comprises the step (S6): adding an organic acid into the residual liquid obtained in the step (S5), and separating Al and rare earth elements.
According to an embodiment of the present invention, in step (S1), the temperature of the calcination is 800-1000 ℃, and is exemplified by 900 ℃.
According to an embodiment of the present invention, in step (S1), the inorganic acid is selected from at least one of hydrochloric acid, nitric acid, sulfuric acid; preferably, the concentration of the mineral acid is 4-6mol/L, and preferably hydrochloric acid.
According to an embodiment of the present invention, in step (S1), the mass ratio of the rare earth slag to the inorganic acid is 1:10.
According to an embodiment of the invention, in step (S1), the temperature of the heat leaching is 30-50 ℃, and is exemplified by 40 ℃.
According to an embodiment of the invention, in step (S2), the ratio by volume of the feed solution containing thorium and rare earth elements to the organic phase is 3 (5-7).
According to an embodiment of the present invention, in step (S2), the organic phase further includes a diluent, which is at least one of kerosene, toluene, and n-heptane.
According to an embodiment of the present invention, in step (S2), the concentration of the extractant is 0.01 to 0.08mol/L, and exemplified by 0.01mol/L, 0.015mol/L, 0.02mol/L, 0.03mol/L, 0.04mol/L, 0.05mol/L, 0.06mol/L, 0.07mol/L, or 0.08mol/L, and preferably from 0.015mol/L to 0.02mol/L.
According to an embodiment of the invention, in step (S2), the extraction temperature is 20-40 ℃, preferably 25-30 ℃; the extraction time is 5-30min, preferably 10-20min.
According to an embodiment of the present invention, in the step (S3), the washing liquid is hydrochloric acid or sulfuric acid, and the concentration of the washing liquid is exemplified by 0.2mol/L.
According to an embodiment of the present invention, in step (S3), the volume ratio of the washing liquid to the organic phase in step (S2) is 5 (5-7).
According to an embodiment of the invention, in step (S4), the stripping liquid is, for example, hydrochloric acid (HCl), or sulfuric acid; preferably, the concentration of the strip liquor is 1-6mol/L, illustratively 1mol/L, 2mol/L, 3mol/L, 4mol/L, 5mol/L or 6mol/L, preferably 6mol/L.
According to an embodiment of the invention, in step (S4), the volume ratio of the stripping liquid to the organic phase in step (S2) is 5 (5-7).
According to an embodiment of the invention, in step (S4), the stripping temperature is 20-40 ℃, preferably 25-30 ℃; the back extraction time is 5-30min, preferably 10-20min.
According to an embodiment of the present invention, the above extraction separation process comprises n-stage extraction, m-stage washing and p-stage back extraction, wherein n is 2 to 6, m is 1 to 4, and p is 1 to 4; preferably n is 2-4, m is 1-3, and p is 1-3.
Illustratively, the organic phase is fed from stage 1, the feed solution containing thorium and rare earth elements is fed from stage n, the wash solution is fed from stage n+m, and the strip solution is fed from stage n+m+p.
According to an embodiment of the present invention, in step (S6), the organic acid is, for example, oxalic acid; the concentration of the organic acid is 0.05-1.5mol/L, preferably 1.4mol/L; the volume ratio of the organic acid to the residual liquid is 1:4-7, preferably 1:5.
According to an embodiment of the present invention, in step (S6), the enrichment mechanism of oxalic acid on rare earth elements is as follows:
2RE 3+ +3H 2 C 2 O 4 +xH 2 O＝RE 2 (C 2 O 4 ) 3 ·xH 2 O↓+6H +
the invention has the beneficial effects that:
(1) Compared with the oxamic acid extractant in the prior art, the extractant represented by DDOA can be completely dissolved in common diluents such as kerosene, so that the loss of the extractant in a water phase is reduced, and the extraction cycle performance is improved.
(2) The extractant represented by 2- (didecylamino) oxalic acid (DDOA) can remove radioactive elements Th in rare earth waste residues, the loading capacity of Th can reach 2.81g/L, and the treatment requirement of ion adsorption of rare earth waste residues can be met. The whole extraction process is carried out at lower acidity, and after 3 times of back extraction by 3mol/L hydrochloric acid, the Th back extraction rate reaches 98 percent. In the course of the extraction, 2mol of DDOA can extract 1mol of Th 4+ . After 5 extraction and stripping cycles, the extraction efficiency of thorium can be maintained at 98%.
(3) After 4-level extraction and 3-level washing, the Th concentration of the outlet of the rare earth water phase is lower than 0.22mg/L, the recovery rate of rare earth elements reaches 91 percent, and the rare earth elements are added (NH) 4 ) 2 SO 4 Ca removal 2+ After that, the recovery rate of rare earth elements reaches 86%; the recovery rate of rare earth elements can reach 80% after the Al ions are separated by adding oxalic acid.
(4) Through the extractant of the application, rare earth metal and thorium can be efficiently separated by cascade stages with fewer stages, the usage amount of the extractant is reduced, the problem of difficult back extraction after the extractant extracts thorium is solved, and the process difficulty is reduced.
Drawings
FIG. 1 is a leaching process of rare earth slag in example 1;
FIG. 2 is a cascade extraction process of example 1;
FIG. 3 is a flow chart for separating rare earth slag in example 1;
FIG. 4 is a graph showing the effect of varying amounts by volume of oxalic acid on depositing rare earth elements (designated REEs) in test example 1;
FIG. 5 is a graph showing the separation effect of different concentrations (0.02 mol/L, 0.06mol/L and 0.08 mol/L) of extractant on rare earth elements and thorium in test example 2;
FIG. 6 is a graph of stripping rates for stripping using different concentrations of HCl in test example 3.
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.
Preparation example 1
0.1mol of didecylamine was added to a reaction vessel cooled in advance in ice water, didecylamine was dissolved with 150mL of methylene chloride, and 0.1mol of oxalyl chloride monoethyl ester was slowly dropped into the vessel at a rate of 30 drops per minute. After the reaction is carried out for half an hour at a temperature of less than 278K, salt generated in methylene dichloride is washed off by deionized water, an organic phase is collected, and 200mL of deionized water is used for washing twice; finally, the methylene dichloride is evaporated to obtain an intermediate product of the ethyl 2- (didecylamino) oxalate.
Cooling the intermediate product to room temperature, transferring the intermediate product to a mixed solution of ethanol and distilled water, adding 0.2mol of NaOH, refluxing for 4 hours, acidifying with 6mol/L of HCl, adding a proper amount of dichloromethane, concentrating the product, and then distilling the dichloromethane solution under reduced pressure to obtain yellow viscous liquid, namely the extractant 2- (didecylamino) oxalic acid. Nuclear magnetic data: 1H NMR (500 MHz, DMSO) delta 3.31-3.07 (m, 4H), 1.60-1.37 (m, 4H), 1.40-1.10 (m, 28H), 0.85 (dd, 6H) 13C NMR (126 MHz, DMSO) delta 165.63,163.42,40.31,31.79,29.45,29.42,29.40,29.20,22.58,14.34.
The yield of 2- (didecylamino) oxalic acid (DDOA) was 85%, and the structure thereof was as follows.
Example 1
In the following embodiments, the cascade process flow ratio is: 6mL of organic phase, 3mL of raw material liquid containing thorium and rare earth elements, 5mL of washing liquid hydrochloric acid, 5mL of back extraction liquid, and the concentration of an extractant is 0.015mol/L, and three-stage washing and four-stage extraction are adopted.
The specific process of recovering thorium and rare earth elements from rare earth waste slag by using an extractant is as follows:
(S1) as shown in FIG. 1, mixing rare earth waste residue after heating and roasting at 900 ℃ with 5mol/L hydrochloric acid, wherein the mass ratio of the rare earth waste residue to the inorganic acid is 1:10, heating and leaching at 40 ℃, and filtering to obtain a raw material liquid containing thorium and rare earth elements, namely a leaching liquid; the raw material liquid also comprises calcium ions and aluminum ions; the content of thorium in the raw material liquid containing thorium and rare earth elements is 13mg/L.
(S2) mixing the extractant prepared in preparation example 1 with 5mL of diluent kerosene to form an organic phase, wherein the concentration of the extractant is 0.015mol/L, and extracting 3mL of raw material liquid containing thorium and rare earth elements at 25 ℃ by adopting the organic phase for 15min.
(S3) washing the organic phase obtained after the extraction in the step (S2) by using 5mL of 0.2mol/L hydrochloric acid washing solution so that the rare earth element is introduced into the aqueous phase and thorium remains in the organic phase.
(S4) carrying out back extraction on the organic phase containing thorium obtained in the step (S3) by using 5mL of 6mol/L back extraction liquid hydrochloric acid, and recovering thorium, wherein the back extraction temperature is 25 ℃ and the time is 10min. As shown in fig. 2, the extraction stage number n is 4, the washing stage number m is 3, and the stripping stage number p is 1; the organic phase is added from stage 1, the feed solution containing thorium and rare earth elements is added from stage 4, the washing solution is added from stage 7, and the stripping solution is added from stage 8.
(S5) As shown in FIG. 3, (NH) is added to the aqueous phase containing the rare earth element obtained in the step (S3) 4 ) 2 SO 4 After removing calcium sulfate, a residual liquid was obtained.
(S6) adding 1mL of oxalic acid with the concentration of 1.4mol/L into the residual liquid obtained in the step (S5), and separating Al and rare earth elements, wherein the volume ratio of the oxalic acid to the residual liquid is 1:5.
When the concentration of the extractant is 0.015mol/l, th in the raffinate after one extraction 4+ The concentration was 4.4mg/L (i.e., first extraction). After 2 to 4 times of extraction, the Th concentration is reduced to below 1 mg/L. Compared to tributyl phosphate, an organophosphine extractant of the present application can extract Th under mild conditions (i.e., pH 4) rather than strongly acidic (e.g., 6mol/L hydrochloric acid, pH 0 or less), using less acid during separation. The residual Th in the rare earth waste residue is less than 0.22mg/L, and the loss of REE is also less. Washing for 1-3 times to wash the rare earth element REE into the water phase. The extractant has good oil solubility, can be subjected to primary back extraction by hydrochloric acid, has simple separation process and less wastewater containing inorganic salts, and has application potential in the field of ion adsorption rare earth radioactive waste residue treatment.
In step (S5), most of Ca 2+ Conversion to CaSO 4 Ca is removed 2+ After that, the REE content was 86%.
Test example 1
Study on effect of oxalic acid on depositing rare earth elements
The enrichment mechanism of oxalic acid to rare earth in the step (S6) is as follows:
2RE 3+ +3H 2 C 2 O 4 +xH 2 O＝RE 2 (C 2 O 4 ) 3 ·xH 2 O↓+6H +
the test was performed by changing the volume of oxalic acid in the step (S6) in the above example 1. FIG. 4 is a graph showing the effect of depositing rare earth elements from different volumes of oxalic acid, and it can be seen from FIG. 4 that 1mL of oxalic acid can effectively precipitate REEs when 5mL of residual liquid is contacted with 1.4mol/L of oxalic acid of different volumes. Under the condition, the recovery rate of REEs after extraction by adopting the extractant is 91 percent, the recovery rate of rare earth elements after oxalic acid precipitation can reach 80 percent, and Ca 2+ The precipitation rate of (2) is about 10%. As the volume of the oxalic acid solution increases,additional oxalic acid to produce Ca (C) 2 O 4 ) 2 . Thus, the present invention selects 1mL oxalic acid, all Al 3+ Are all maintained in the aqueous phase to avoid Al when obtaining a single RE product 3+ Influence on extraction.
Test example 2
Research on separation effect of extractant with different concentrations on rare earth elements and thorium
Taking DDOA as an example, as shown in FIG. 5, the separation of rare earth elements and thorium by the extractants of different concentrations (0.02 mol/L, 0.06mol/L, 0.08 mol/L) was studied and the concentration of the extractant in the step (S2) in the above-mentioned example 1 was changed to conduct the test. Namely, the rare earth waste residue is separated when the concentration of the extractant is respectively 0.02mol/L, 0.06mol/L and 0.08mol/L. As can be seen from FIG. 5, when the extractant concentration was 0.02mol/L, the extraction efficiency of Th was 88%, and at this time, rare earth elements were hardly extracted. Therefore, the high selectivity of the extractant can simplify the separation process and reduce the dosage of the extractant. When the concentration of the extractant is increased to 0.06mol/L and 0.08mol/L, the extraction efficiency of each REE is improved, lu 3+ The extraction efficiency of (2) exceeds 40%. Although extraction efficiency of Th is still high, separation effect of REE and Th is not good. It can be seen that the concentration of extractant is relative to Th 4+ The effect of extraction is small. In addition, the Chemical Oxygen Demand (COD) of the raffinate in the whole experiment is less than 105mg/L, and the extractant has low water solubility, so that the water pollution can be reduced. Sm at the lowest concentration of DDOA (i.e., 0.02 mol/L) 3+ Is higher than Lu 3+ . But under the same conditions Lu 3+ Is far more difficult than Sm 3+ Thus, th was selected in the subsequent study 4+ And Lu 3+ A comparison is made.
With 0.04mol/L extractant, the loadings of Th and Lu reached 2.81g/L and 1.86g/L, respectively, and the extractant was present as dimers due to hydrogen ion interactions on DDOA, which limited its loading capacity. Because the concentration of Th in the actual rare earth waste residue leaching solution is far lower than 100mg/L, the loading capacity of Th can meet the requirement of waste residue treatment. In the invention, the extractant does not generate obvious emulsification after multiple extractions.
Test example 3
Research on stripping effect
The test was performed by changing the concentration of the strip hydrochloric acid in step (S4) in example 1. FIG. 6 is a graph of stripping rates using different concentrations of HCl, and as can be seen from FIG. 6, when stripping is performed using 1mol/LHCl, the second stripping rate and the third stripping rate are not significantly changed, and are both 15%. However, under the condition of 3mol/L HCl, the first stripping rate of Th can be increased to 78%, and after 3 times of stripping, the stripping rate reaches about 98% (namely, the three-stage stripping rate is about 98%). In the subsequent experiments, hydrochloric acid with higher concentration of 6mol/L is selected for back extraction to ensure that not only thorium can be back extracted, but also other impurities can be cleaned in the back extraction process. Good stripping performance of DDOA facilitates fractionation and product enrichment.
Research on the cycle performance of extractant
In this study, each cycle was first extracted and back extracted with 6mol/L hydrochloric acid. The specific process is as follows: the procedure of example 1 was followed, wherein 5ml of a freshly prepared organic phase (wherein the concentration of the extractant was 0.02 mol/L) was extracted to give a raw material liquid, followed by stripping using 5ml of 6mol/L hydrochloric acid as a cycle, and after the completion of the stripping, the raw material liquid was extracted with the organic phase after the stripping in the previous cycle, and stripping was performed, and the extraction rates were measured for each cycle to give five extraction rates.
After five cycles, the extraction rate of thorium can be maintained above 98%. The phase separation is obvious, the organic phase and the water phase are clear, and the volume of the organic phase is basically unchanged. The organic phase had substantially the same properties before and after extraction, with no significant change in color and performance. The above results indicate that the physicochemical properties of DDOA remain stable after multiple cycles. The recycling properties of the organic phase are important in terms of extraction and separation. Extraction of the easily extractable components and stripping of the difficult-to-extract components are accomplished in a continuous cycle. After repeated circulation, the extraction capacity of the extractant should not be significantly reduced. The extractant pair Th represented by DDOA in the invention 4+ Has high extraction efficiency and Th 4+ Is easy to be back-extracted.
The embodiments of the present invention have been described above by way of example. However, the scope of the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc. made by those skilled in the art, which fall within the spirit and principles of the present invention, are intended to be included within the scope of the present invention.
Claims (10)
1. An extractant, characterized in that it has a structure represented by the following formula 1:
wherein R may be the same or different and are independently selected from C 10-20 An alkyl group.
2. The extractant according to claim 1, wherein the extractant is 2- (didecylamino) oxalic acid (DDOA) which is a compound represented by the following formula 2.
Preferably, the extractant is used to separate thorium and rare earth elements.
Preferably, the rare earth element is selected from at least one of La, ce, pr, nd, pm, sm, eu, sc, Y, gd, tb, dy, ho, er, tm, yb, lu.
Preferably, when the concentration of the extractant is 0.04mol/L, the loading of the extractant to thorium is 2-3g/L.
3. Extractant according to claim 1 or 2, characterized in that the extractant has a water solubility of 110mg/L or less.
Preferably, the extractant has good stripping performance, and the stripping rate reaches 98% after three times of stripping under the condition of 3mol/L hydrochloric acid stripping.
Preferably, the extractant has good reusability, and after 5 extraction and stripping cycles, the extraction efficiency of thorium remains at 98%.
4. A process for the preparation of an extractant according to any one of claims 1 to 3, comprising the steps of:
(1) Mixing and reacting a compound shown in a formula A with oxalyl chloride monoethyl ester to prepare an intermediate product, namely a compound shown in a formula B;
HNR 2 formula A;
wherein R may be the same or different and are independently selected from C 10-20 An alkyl group;
(2) And (3) reacting the intermediate product in the step (1) with inorganic base, and then acidizing by acid to prepare the extractant.
5. The process according to claim 4, wherein in step (1), the temperature of the reaction is between 0 and 8 ℃, preferably between 0 and 5 ℃.
Preferably, in step (1), the molar ratio of the compound of formula A to oxalyl chloride monoethyl ester is (0.05-2): 1.
Preferably, the compound of formula a is didecylamine.
Preferably, in step (2), the molar ratio of the compound represented by formula A to the inorganic base is 1 (1-3).
Preferably, in step (2), the acid is hydrochloric acid or sulfuric acid; the concentration of the acid is 4-8mol/L.
6. Use of an extractant according to any one of claims 1 to 3 in the separation of thorium and rare earth elements.
7. A method for recovering thorium and rare earth elements from rare earth waste residues, which is characterized by comprising the following steps:
(S1) roasting rare earth waste residues, mixing the rare earth waste residues with inorganic acid, and heating and leaching to obtain a raw material liquid containing thorium and rare earth elements;
(S2) extracting with a feed solution containing organic phase thorium and rare earth elements containing the extractant of any one of claims 1 to 3;
(S3) washing the organic phase obtained after the extraction in step (S2) with a washing liquid so that the rare earth element is incorporated into the aqueous phase and thorium remains in the organic phase;
(S4) stripping the organic phase containing thorium obtained in the step (S3) by using a stripping liquid to recover thorium.
8. The method according to claim 7, wherein in the step (S1), calcium ions and/or aluminum ions are further included in the raw material liquid.
Preferably, the method further comprises the step (S5): adding (NH) to the aqueous phase containing the rare earth element obtained in the step (S3) 4 ) 2 SO 4 After removing calcium sulfate, a residual liquid was obtained.
Preferably, the method further comprises the step (S6): adding an organic acid into the residual liquid obtained in the step (S5), and separating Al and rare earth elements.
9. The method according to claim 7 or 8, wherein in step (S1), the temperature of calcination is 800-1000 ℃.
Preferably, in step (S1), the inorganic acid is selected from at least one of hydrochloric acid, nitric acid, sulfuric acid; preferably, the concentration of the mineral acid is 4-6mol/L, preferably hydrochloric acid.
Preferably, in step (S2), the organic phase further includes a diluent, and the diluent is at least one of kerosene, toluene, and n-heptane.
Preferably, in step (S2), the concentration of the extractant is 0.01 to 0.08mol/L.
10. The method according to any one of claims 7 to 9, wherein in step (S3), the washing liquid is hydrochloric acid or sulfuric acid, and the concentration of the washing liquid is exemplified by 0.2mol/L.
Preferably, in step (S4), the strip liquor is hydrochloric acid or sulfuric acid; preferably, the concentration of the strip liquor is 1-6mol/L.
Preferably, the extraction separation process comprises n-level extraction, m-level washing and p-level back extraction, wherein n is 2-6, m is 1-4, and p is 1-4; preferably n is 2-4, m is 1-3, and p is 1-3.
Preferably, in step (S6), the organic acid is oxalic acid; the concentration of the organic acid is 0.05-1.5mol/L; the volume ratio of the organic acid to the residual liquid is 1:4-7.
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Non-Patent Citations (4)
| Title |
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| CHAO BIE, YUN GAO, JIA SU, YAMIN DONG, XIANGGUANG GUO, XIAOQI SUN: "The efficient separation of thorium from rare earth using oxamic acid in hydrochloric acid medium", SEPARATION AND PURIFICATION TECHNOLOGY, vol. 251, 12 July 2020 (2020-07-12) * |
| CHAO BIE等: "The selective recovery of rare earth from radioactive waste residue using improved oxamic acid for environmental and resource concerns", SSRN, 3 November 2021 (2021-11-03) * |
| GUO, CHUANGLONG，ZHI, YONGGANG: "Effective solvent extraction of La, Ce and Pr from hydrochloric acid with a novel extractant N, N-dihexyloxamic acid", JOURNAL OF CHEMICAL TECHNOLOGY AND BIOTECHNOLOGY, vol. 92, no. 7, 19 December 2016 (2016-12-19), pages 1596 - 1600 * |
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