CN115814602A - Self-microporous polymer membrane for lithium isotope separation, preparation method thereof and electrodialysis separation application - Google Patents
Self-microporous polymer membrane for lithium isotope separation, preparation method thereof and electrodialysis separation application Download PDFInfo
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- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 69
- 229920005597 polymer membrane Polymers 0.000 title claims abstract description 69
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 68
- 238000000926 separation method Methods 0.000 title claims abstract description 62
- 238000000909 electrodialysis Methods 0.000 title claims abstract description 55
- 238000005372 isotope separation Methods 0.000 title claims abstract description 39
- 238000002360 preparation method Methods 0.000 title abstract description 19
- 239000012528 membrane Substances 0.000 claims abstract description 69
- 150000003983 crown ethers Chemical class 0.000 claims abstract description 55
- 229920000642 polymer Polymers 0.000 claims abstract description 54
- 238000000034 method Methods 0.000 claims abstract description 40
- 239000003011 anion exchange membrane Substances 0.000 claims abstract description 31
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 19
- 239000000178 monomer Substances 0.000 claims abstract description 16
- 239000002904 solvent Substances 0.000 claims abstract description 15
- 230000001546 nitrifying effect Effects 0.000 claims abstract description 4
- 239000000243 solution Substances 0.000 claims description 41
- QSBFECWPKSRWNM-UHFFFAOYSA-N dibenzo-15-crown-5 Chemical compound O1CCOCCOC2=CC=CC=C2OCCOC2=CC=CC=C21 QSBFECWPKSRWNM-UHFFFAOYSA-N 0.000 claims description 25
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 claims description 18
- HEDRZPFGACZZDS-UHFFFAOYSA-N Chloroform Chemical compound ClC(Cl)Cl HEDRZPFGACZZDS-UHFFFAOYSA-N 0.000 claims description 18
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 10
- DTQVDTLACAAQTR-UHFFFAOYSA-N Trifluoroacetic acid Chemical compound OC(=O)C(F)(F)F DTQVDTLACAAQTR-UHFFFAOYSA-N 0.000 claims description 10
- 229920006254 polymer film Polymers 0.000 claims description 10
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 9
- 239000007810 chemical reaction solvent Substances 0.000 claims description 9
- 229910001416 lithium ion Inorganic materials 0.000 claims description 9
- PMZURENOXWZQFD-UHFFFAOYSA-L Sodium Sulfate Chemical compound [Na+].[Na+].[O-]S([O-])(=O)=O PMZURENOXWZQFD-UHFFFAOYSA-L 0.000 claims description 8
- 239000008151 electrolyte solution Substances 0.000 claims description 8
- NWZSZGALRFJKBT-KNIFDHDWSA-N (2s)-2,6-diaminohexanoic acid;(2s)-2-hydroxybutanedioic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O.NCCCC[C@H](N)C(O)=O NWZSZGALRFJKBT-KNIFDHDWSA-N 0.000 claims description 7
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 7
- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine monohydrate Substances O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-N 0.000 claims description 7
- 229910017604 nitric acid Inorganic materials 0.000 claims description 7
- AMXOYNBUYSYVKV-UHFFFAOYSA-M lithium bromide Chemical compound [Li+].[Br-] AMXOYNBUYSYVKV-UHFFFAOYSA-M 0.000 claims description 6
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 6
- HSZCZNFXUDYRKD-UHFFFAOYSA-M lithium iodide Chemical compound [Li+].[I-] HSZCZNFXUDYRKD-UHFFFAOYSA-M 0.000 claims description 6
- 229910052938 sodium sulfate Inorganic materials 0.000 claims description 6
- 235000011152 sodium sulphate Nutrition 0.000 claims description 6
- 150000003839 salts Chemical class 0.000 claims description 5
- 239000012298 atmosphere Substances 0.000 claims description 4
- NKDDWNXOKDWJAK-UHFFFAOYSA-N dimethoxymethane Chemical compound COCOC NKDDWNXOKDWJAK-UHFFFAOYSA-N 0.000 claims description 4
- 229910052751 metal Inorganic materials 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
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- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 3
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 3
- XQHAGELNRSUUGU-UHFFFAOYSA-M lithium chlorate Chemical compound [Li+].[O-]Cl(=O)=O XQHAGELNRSUUGU-UHFFFAOYSA-M 0.000 claims description 3
- MHCFAGZWMAWTNR-UHFFFAOYSA-M lithium perchlorate Chemical compound [Li+].[O-]Cl(=O)(=O)=O MHCFAGZWMAWTNR-UHFFFAOYSA-M 0.000 claims description 3
- 229910001486 lithium perchlorate Inorganic materials 0.000 claims description 3
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 claims description 3
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 2
- RTZKZFJDLAIYFH-UHFFFAOYSA-N Diethyl ether Chemical compound CCOCC RTZKZFJDLAIYFH-UHFFFAOYSA-N 0.000 abstract description 25
- 230000008901 benefit Effects 0.000 abstract description 7
- 230000007613 environmental effect Effects 0.000 abstract description 7
- YSSSPARMOAYJTE-UHFFFAOYSA-N dibenzo-18-crown-6 Chemical compound O1CCOCCOC2=CC=CC=C2OCCOCCOC2=CC=CC=C21 YSSSPARMOAYJTE-UHFFFAOYSA-N 0.000 abstract description 5
- 238000004134 energy conservation Methods 0.000 abstract description 4
- 150000004985 diamines Chemical class 0.000 abstract description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 20
- 150000002500 ions Chemical class 0.000 description 19
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 16
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- 238000012986 modification Methods 0.000 description 5
- 238000001179 sorption measurement Methods 0.000 description 5
- 239000000126 substance Substances 0.000 description 5
- KDLHZDBZIXYQEI-UHFFFAOYSA-N Palladium Chemical compound [Pd] KDLHZDBZIXYQEI-UHFFFAOYSA-N 0.000 description 4
- 239000003054 catalyst Substances 0.000 description 4
- 238000012512 characterization method Methods 0.000 description 4
- 238000003795 desorption Methods 0.000 description 4
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- 229910003002 lithium salt Inorganic materials 0.000 description 3
- 159000000002 lithium salts Chemical class 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- UKVIEHSSVKSQBA-UHFFFAOYSA-N methane;palladium Chemical compound C.[Pd] UKVIEHSSVKSQBA-UHFFFAOYSA-N 0.000 description 3
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 3
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- YMWUJEATGCHHMB-UHFFFAOYSA-N Dichloromethane Chemical compound ClCCl YMWUJEATGCHHMB-UHFFFAOYSA-N 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 2
- YZCKVEUIGOORGS-NJFSPNSNSA-N Tritium Chemical compound [3H] YZCKVEUIGOORGS-NJFSPNSNSA-N 0.000 description 2
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- FGIUAXJPYTZDNR-UHFFFAOYSA-N potassium nitrate Chemical compound [K+].[O-][N+]([O-])=O FGIUAXJPYTZDNR-UHFFFAOYSA-N 0.000 description 2
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 description 2
- 238000000956 solid--liquid extraction Methods 0.000 description 2
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- 229910052722 tritium Inorganic materials 0.000 description 2
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- ZSLUVFAKFWKJRC-IGMARMGPSA-N 232Th Chemical compound [232Th] ZSLUVFAKFWKJRC-IGMARMGPSA-N 0.000 description 1
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 1
- 229910013553 LiNO Inorganic materials 0.000 description 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 229910052776 Thorium Inorganic materials 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 125000003277 amino group Chemical group 0.000 description 1
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- 238000010438 heat treatment Methods 0.000 description 1
- 239000001307 helium Substances 0.000 description 1
- 229910052734 helium Inorganic materials 0.000 description 1
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 description 1
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- 125000000449 nitro group Chemical group [O-][N+](*)=O 0.000 description 1
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- OTYBMLCTZGSZBG-UHFFFAOYSA-L potassium sulfate Chemical compound [K+].[K+].[O-]S([O-])(=O)=O OTYBMLCTZGSZBG-UHFFFAOYSA-L 0.000 description 1
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- 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
Abstract
The invention discloses a self-contained microporous polymer membrane for lithium isotope separation, a preparation method and electrodialysis separation application thereof, wherein the lithium isotope separation membrane is a crown ether main chain type self-contained microporous polymer membrane, and the preparation method specifically comprises the following steps: nitrifying and hydrogenating the monomer dibenzocrown ether to obtain 2,6-diamino-dibenzocrown ether; passing the obtained diamine monomer through
Base polymerization is carried out to prepare a crown ether main chain type self-possessed microporous polymer; and (3) obtaining the polymer membrane with the micropores by a solvent volatilization method. The electrodialysis is mainly based on a system of a cathode plate, an electrodialysis membrane group and an anode plate which are arranged in sequence; the electrodialysis membrane group is composed of anion exchange membranes, the polymer membranes with micropores and the anion exchange membranes which are arranged in sequence. The invention has a porous polymer membrane pair 6 Li + / 7 Li + The selective separation performance is excellent, the single-stage selectivity is 1.16, the membrane preparation is simple, the separation process can be continuous, and the selective separation method has the advantages of environmental protection, energy conservation, high efficiency and the like.
Description
Technical Field
The invention relates to the technical field of isotope separation, in particular to a self-provided microporous polymer membrane for lithium isotope separation, a preparation method thereof and an application of electrodialysis separation.
Background
Lithium (Li) is the lightest metal and one of its uses is to provide a new energy source. It is estimated that 1kg of lithium contains energy corresponding to approximately 4000 tonnes of standard coal and can generate at least 10000 kwh. Lithium element is naturally present 6 Li and 7 two stable isotopes of Li, with abundances of about 7.5% and 92.5%, respectively. 6 Li and 7 both Li isotopes play an extremely important role in the nuclear power industry, 6 after Li is bombarded by neutrons, tritium (T) and helium (He) are generated, so that tritium in the fusion reactor can be continuously proliferated, therefore 6 Li is the requisite nuclear fusion reactor fuel. 7 Li is commonly used as a core coolant and a heat transfer agent for nuclear fusion reactors, 7 li can also act as a thorium stack molten salt medium. 6 Li and 7 the roles of Li are different, so that the development of a green and efficient lithium isotope separation method is of great significance.
Methods for separating lithium isotopes can be roughly classified into chemical methods and physical methods. The chemical method comprises a lithium amalgam method, ion exchange chromatography, extraction, fractional crystallization, fractional precipitation and the like; physical methods include electromagnetic methods, molten salt electrolysis methods, electron transfer, molecular distillation, laser separation, and the like. Currently, the only methods that have been used for industrial production are the lithium amalgam method. However, the lithium amalgam method uses a large amount of metallic mercury, is limited by insufficient mercury amount, is difficult to improve the production capacity on a large scale, and cannot meet the requirement of civil nuclear energy on lithium isotopes. In addition, the hazard of mercury to the human body and the environment is another important factor limiting the development of mercury. In order to avoid the use of toxic mercury, it is critical to develop alternative methods with good separation factors. Among them, solvent extraction and solid-liquid extraction using crown ether or polymeric crown ether as a lithium isotope acceptor are the most widely studied methods with good separation factors at present.
The crown ether-based solvent extraction method mainly utilizes the neutral chelating extractant of crown ether and the like to carry out the extraction 6 Li + And 7 Li + the ion selection effect of (2) and a chemical exchange method for realizing isotope exchange and enrichment in an exchange link. However, the process usually has the technical problems of difficult reutilization of crown ether, large using amount of solvent, easy back mixing and the like. In order to better utilize the extraction performance of crown ether and avoid the shortage of solvent extraction, the research is carried out on the immobilization of crown ether and polymer by using the polymer as a carrier and by grafting and other technologies, so that isotopes are separated by a solid-liquid extraction method.
However, the above extraction process for separating lithium isotopes still needs to be further improved in terms of simplicity of operation, environmental friendliness, and the like.
Disclosure of Invention
In view of the above, the present invention provides a self-microporous polymer membrane for lithium isotope separation, a preparation method thereof, and an application of electrodialysis separation, wherein the self-microporous polymer membrane provided by the present invention has an ion transport channel with a lithium isotope selection effect, can separate lithium isotopes through a membrane separation process, and has the advantages of simple operation, continuous operation, environmental protection, and the like.
The invention provides a self-contained microporous polymer membrane for lithium isotope separation, which is prepared from a crown ether main chain type polymer, wherein the crown ether main chain type polymer has a structure shown in a formula 1, and n is the polymerization degree;
preferably, the self-microporous polymer membrane has hydrophilicity.
Further preferably, the thickness of the polymer membrane with the micropores is 60 to 80 μm.
The invention provides a preparation method of the polymer membrane with micropores, which comprises the following steps:
s1, passing 2,6-diamino-dibenzo-15-crown-5-ether through
Base polymerization to obtain a crown ether main chain type polymer shown as a formula 1; the 2,6-diamino-dibenzo-15-crown-5-ether has a structure shown in formula 2;
s2, dissolving the crown ether main chain type polymer by using a solvent, and then volatilizing the solvent to obtain the polymer film with the micropores;
preferably, in step S1, 2,6-diamino-dibenzo-15-crown-5-ether represented by said formula 2 is obtained in the following manner:
firstly, using dibenzo-15-crown-5-ether as a monomer, chloroform as a reaction solvent and acetic acid as a dehydrating agent, and nitrifying the monomer by using nitric acid to obtain 2,6-dinitro-dibenzo-15-crown-5-ether; specifically, the molar ratio of nitric acid to monomer is 4:1, acetic acid is excessive, and the nitration condition is 70 ℃ for overnight reaction.
Then, the obtained 2,6-dinitro-dibenzo-15-crown-5-ether was reduced with hydrazine hydrate in a protective atmosphere using ethanol as a reaction solvent to obtain the 2,6-diamino-dibenzo-15-crown-5-ether. Specifically, the molar ratio of the hydrazine hydrate to 2,6-dinitro-dibenzo-15-crown-5-ether is 50: 1, an excessive amount of palladium-carbon catalyst is preferably adopted, the reduction condition is 90 ℃ for overnight reaction, and nitrogen is preferably selected as the protective atmosphere.
Preferably, in step S1, the method comprises
The Base polymerization is specifically as follows: reacting 2,6-diamino-dibenzo-15-crown-5-ether with dimethoxymethane for a certain time by using trifluoroacetic acid as a reaction solvent to obtain the crown ether main chain type polymer shown in the formula 1.
Preferably, in step S2, the solvent used for dissolving the crown ether main chain type polymer is chloroform, the mass concentration of the obtained solution is 1-2 wt.%, and the solvent is volatilized at room temperature to obtain the polymer membrane with micropores.
The invention provides a process for separating a polymer membrane having micropores as described above 6 Li and 7 application in Li isotopes.
The invention also provides a process for separating a polymer membrane having micropores from the membrane in combination with electrodialysis, as described above 6 Li and 7 application in Li isotopes.
Preferably, the electrodialysis separation is carried out by adopting a system comprising a self-polymerization microporous polymer membrane, wherein the system comprises a power supply and a cathode plate, an electrodialysis membrane group and an anode plate which are sequentially arranged; the electrodialysis membrane group comprises an anion exchange membrane, a polymer membrane with micropores and an anion exchange membrane which are sequentially arranged; a cathode chamber is formed between the cathode plate and the adjacent anion exchange membrane, and an anode chamber is formed between the anode plate and the adjacent anion exchange membrane; two poles of the power supply are respectively connected with the cathode plate and the anode plate; supplying an electrode solution to the cathode and anode compartments, supplying a solution containing a metal salt to the system 6 Li + Ions and 7 Li + an ionic electrolyte solution.
Preferably, the sequentially arranged anion exchange membranes are all commercial membranes AMX.
Preferably, the electrode solution introduced into the cathode chamber and the anode chamber is a sodium sulfate solution, and the concentration of the sodium sulfate solution can be 0.3 mol.L -1 。
Preferably, the electrolyte is one or more of lithium nitrate, lithium chloride, lithium bromide, lithium iodide, lithium carbonate, lithium sulfate, lithium chlorate, lithium perchlorate and lithium hydroxide.
Preferably, the electrodialysis separation is maintained in a constant current mode.
Compared with the prior art, the invention provides a self-provided microporous polymer membrane for lithium isotope separation, a preparation method thereof, electrodialysis separation application and the like. The membrane for lithium isotope separation is a crown ether main chain type self-provided microporous polymer membrane, and the crown ether main chain type polymer has a structure shown in a formula 1;the preparation process comprises the following steps: using dibenzo crown ether as a monomer, and obtaining 2,6-diamino-dibenzo-15-crown-5-ether (the structure is shown in formula 2) by nitration and hydrogenation reduction; passing the obtained diamine monomer through
Preparing a crown ether main chain type self-contained microporous polymer with a structure shown in a formula 1 by Base polymerization; and (3) obtaining the polymer membrane with the micropores by a solvent volatilization method.
The invention can select dibenzo crown ether as a monomer to prepare the crown ether main chain type self-provided microporous polymer film, and the crown ether is directly used as a polymer main chain to give full play to the effect of the polymer main chain 6 Li + 、 7 Li + Ion selection in separation. The embodiment of the invention combines amino modification on crown ether
The polymer main chain is directly prepared by one-step reaction of Base (TB) polymerization, the reaction condition is simple and mild, and the obtained polymer has excellent mechanical property. The TB unit is a rigid nitrogen-containing six-membered ring structure, the introduction of which causes the polymer to be distorted and folded, and is self-microporous 6 Li + 、 7 Li + Provides an ion channel; meanwhile, the crown ether can improve the hydrophilicity of the membrane, so that the membrane still has ideal ion flux under the condition of no charge. Most of the methods reported at present are to modify a polymer substrate by using a post-modification manner to introduce crown ether, and one of the innovations of the preparation method in the invention is as follows: the polymerization reaction directly takes crown ether as a main chain, and an ion transmission channel is constructed at the same time, so that the prepared crown ether main chain type self-possessed microporous polymer membrane has excellent ion selective separation performance and higher ion flux, and is beneficial to membrane separation of lithium isotopes; the film making process has simple and controllable steps and high efficiency.
On the basis, the invention has another innovation point that: the polymer membrane with the micropores is combined with an electrodialysis membrane separation process for lithium isotope separation. The electrodialysis is based on a cathode plate, a cathode plate and a cathode plate which are arranged in sequence,A system of electrodialysis membrane groups and anode plates; wherein the electrodialysis membrane group can be composed of commercial anion exchange membranes-the self-microporous polymer membrane-commercial anion exchange membranes arranged in sequence. The invention combines the polymer membrane with micropores with electrodialysis to separate lithium isotope, and the crown ether pair is based on 6 Li + 、 7 Li + Under the driving action of an external electric field, 6 Li + has an electrical mobility greater than 7 Li + And the two have synergistic effect, so that the separation efficiency of the lithium isotope is effectively improved. In the embodiment of the present invention, it is, 6 Li +/7 Li + the selective separation performance is excellent, and the single-stage selectivity is 1.16. Therefore, the method for separating the lithium isotopes has the characteristics of safety, environmental protection, continuous and stable separation process, energy conservation, high efficiency and the like.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the embodiments or the prior art descriptions will be briefly described below, it is obvious that the drawings in the following description are only embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the provided drawings without creative efforts.
FIG. 1 is a nuclear magnetic hydrogen spectrum of PIM-DB15C5-TB prepared in example 1;
FIG. 2 is a graph of the contact angle of a dibenzo-15-crown-5-ether-based self-microporous polymer membrane of example 1;
FIG. 3 is a graph showing the nitrogen adsorption and desorption of dibenzo-15-crown-5-ether-based polymer membrane having micropores in example 1;
FIG. 4 is a graph of the room temperature stress strain curve of the dibenzo-15-crown-5-ether-based self-microporous polymer membrane of example 1;
FIG. 5 is a schematic view of the operation of the permeation device described in example 2;
FIG. 6 is a graph of the static diffusion profile of dibenzo-15-crown-5-ether-based self-microporous polymer membrane to lithium nitrate in example 1;
FIG. 7 is an embodimentExample 1 pairs of self-assembled microporous polymer membranes based on dibenzo-15-crown-5-Ether 6 Li + 、 7 Li + Static diffusion separation curve diagram of mixed solution;
FIG. 8 is a schematic diagram of the operating principle of the electrodialysis system as described in example 3;
FIG. 9 is a dibenzo-15-crown-5-ether-based self-assembled microporous polymer membrane pair of example 3 6 Li + 、 7 Li + Distributing the electrodialysis result of the mixed solution;
FIG. 10 is a graph of the static diffusion separation of dibenzo-15-crown-5-ether based self-microporous polymer membrane from an actual lithium salt system in example 4;
fig. 11 is a graph of the electrodialysis results of self-microporous polymer membranes of dibenzo-15-crown-5-ether in example 4 versus an actual lithium salt system.
Detailed Description
The technical solutions in the embodiments of the present application are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present application, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
The invention provides a self-contained microporous polymer membrane for lithium isotope separation, which is prepared from a crown ether main chain type polymer, wherein the crown ether main chain type polymer has a structure shown in a formula 1, and n is the polymerization degree;
compared with the extraction process, the membrane separation process based on crown ether has the advantages of greenness, environmental protection, simplicity, convenience, continuous operation and the like, and is a promising lithium isotope separation method. Self-microvoided polymers have inherent microvoids (typically < 2nm in pore size) due to limited polymer chain stacking and can be readily dissolved in common organic solvents by solution casting and sprayingThe coating is processed simply and exhibits excellent film-forming ability. Furthermore, the intrinsic micropores of the polymer membrane with micropores can provide abundant ion channels for ion transmission. The invention combines crown ether with the ion transport channel, and is expected to construct an ion transport channel with lithium isotope selection effect. Furthermore, under the action of an external electric field, 6 Li + has an electrical mobility greater than 7 Li + The electron physical migration and the ion selection effect of the crown ether are coupled, so that the extraction efficiency of the lithium isotope can be effectively improved.
The invention expects to combine a membrane separation method and an electric field isotope separation method through a crown ether-based self-contained microporous polymer membrane, design an electrodialysis membrane separation system, and enhance the separation effect of lithium isotopes by utilizing the synergistic effect of the two separation methods on the separation of the lithium isotopes, thereby achieving the purpose of quickly and efficiently separating the lithium isotopes.
The preferred embodiment of the present invention provides a method for preparing a lithium isotope separation membrane, which is a method for preparing a self-microporous polymer membrane for lithium isotope separation, comprising the steps of:
(1) Using dibenzo-15-crown-5-ether as a monomer, chloroform as a reaction solvent and acetic acid as a dehydrating agent, and nitrifying the monomer by using nitric acid to obtain 2,6-dinitro-dibenzo-15-crown-5-ether;
(2) Carrying out catalytic reduction on 2,6-dinitro-dibenzo-15-crown-5-ether obtained in the step (1) by using hydrazine hydrate in a reaction solvent ethanol under the protection of nitrogen and by using palladium-carbon to obtain 2,6-diamino-dibenzo-15-crown-5-ether;
(3) Subjecting the reduction product 2,6-diamino-dibenzo-15-crown-5-ether obtained in the step (2) to
Base is polymerized to prepare a crown ether main chain type self-contained microporous polymer;
(4) And (3) dissolving the crown ether main chain type self-micropore polymer obtained in the step (3) by using an organic solvent, and obtaining the self-micropore polymer membrane for separating lithium isotopes by using an organic solvent volatilization method.
In the invention, the crown ether monomer of the crown ether main chain type self-contained micropore polymer is dibenzo-15-crown-5-ether and can be commercially available. In the embodiment of the invention, the dibenzocrown ether monomer and nitric acid are subjected to nitration reaction, and the molar ratio of the nitric acid to the dibenzo-15-crown-5-ether is preferably 4: 1. The nitration reaction is preferably carried out in chloroform as solvent, with an excess of acetic acid; the reaction conditions are specifically as follows: the reaction is carried out overnight at 70 ℃, and then extraction, water washing and the like are carried out after decompression concentration, thus obtaining 2,6-dinitro-dibenzo-15-crown-5-ether. In the present invention, the operations such as extraction and washing are not particularly limited.
The reaction formula is preferably as follows:
in the embodiment of the invention, 2,6-dinitro-dibenzocrown ether obtained by nitration is subjected to hydrogenation reduction reaction to obtain 2,6-diamino-dibenzocrown ether (which is 2,6-diamino-dibenzo-15-crown-5-ether) with the structure shown in the specification;
in the invention, the hydrogenation reduction specifically comprises the following steps: the nitro group in the 2,6-dinitro-dibenzocrown ether obtained is reduced to an amino group using ethanol as a reaction solvent and hydrazine hydrate as a reducing agent in a protective atmosphere such as nitrogen. Preferably, the molar ratio of hydrazine hydrate to 2,6-dinitro-dibenzocrown ether is 50: 1. Further, in the reduction reaction of the embodiment of the present invention, it is preferable to use a palladium on carbon catalyst (Pd/C) and to add an excess amount of the catalyst, and the reaction conditions are 90 ℃ overnight.
After 2,6-diamino-dibenzo-15-crown-5-ether shown in formula 2 is obtained, the invention provides
The Base is polymerized to prepare the crown ether main chain type self-polymerization microporous polymer with a structural formula shown as formula 1, PIM-DB15C5-TB for short。
In the present invention, in the above-mentioned step
The Base polymerization is specifically as follows: adding the obtained reduction product 2,6-diamino-dibenzocrown ether into a round-bottom flask preferably according to the mol ratio of the reduction product to dimethoxymethane of 1: 5, and dropwise adding trifluoroacetic acid into an ice-water bath under the protection of nitrogen atmosphere; the mass-volume ratio of 2,6-diamino-dibenzocrown ether to trifluoroacetic acid can be 1 g: 5-15mL. After the dropwise addition is finished, stirring the obtained mixed solution at normal temperature to react for 48-72 hours, preferably for 48 hours; the normal temperature is generally 10-40 ℃, and the conventional stirring operation is adopted.
The reaction formula is preferably as follows:
in the structure of the self-microporous polymer PIM-DB15C5-TB based on dibenzo-15-crown-5-ether and Troger's base, the TB unit is a rigid nitrogen-containing six-membered ring structure, so that the crown ether main chain type polymer is twisted and folded and self-microporous, and can be used as a microporous polymer 6 Li + 、 7 Li + Provides an ion channel. Meanwhile, the obtained polymer with the structure of formula 1 has excellent mechanical properties. The polymer main chain is prepared by directly utilizing the crown ether (the crown ether is the main chain), and the preparation steps are simpler; in formula 1, n is the degree of polymerization.
The invention adopts the crown ether main chain type polymer to prepare the self-possessed microporous membrane for lithium isotope separation. The PIM-DB15C5-TB polymer separation membrane is a self-microporous polymer, and the existence of a TB structure (a nitrogen-containing six-membered ring in the structure and a structure in a circle of the following formula) of the membrane introduces free volume required by ion transmission, so that the flux of the membrane has certain advantages compared with the flux of a traditional compact membrane.
In addition, the PIM-DB15C5-TB membrane in the application is uncharged (no ion functional group is introduced), and the uncharged characteristic of the membrane enables crown ether to have better ion selection on lithium isotopes, and the selectivity of the membrane has obvious advantage although flux is sacrificed to a certain extent. The polymer membrane with the micropores has hydrophilicity, and the crown ether structure can improve the hydrophilicity of the membrane, so that the membrane still has ideal ion flux under the condition of no charge.
In the invention, the film is prepared by obtaining the polymer film with micropores by an organic solvent volatilization method; the method comprises the following steps: the solvent used for dissolving the polymer is preferably chloroform, the mass concentration of the polymer solution is generally 1 to 2wt.%, and the mass concentration is preferably 1.25wt.%; the polymer film can be placed in a glass culture dish to volatilize the organic solvent at room temperature, and the polymer film with the micropores for separating the lithium isotopes is obtained. Specifically, the thickness of the lithium isotope separation membrane is preferably 60 to 80 μm.
The polymer membrane with micropores can be applied to membrane separation 6 Li and 7 li isotope, and further, the invention also provides an electrodialysis separation application of the polymer membrane with micropores for lithium isotope separation.
The previously reported crown ether extraction separation methods mostly adopt (1) solvent extraction agent and (2) adsorption type material, and the two disadvantages include: for (1), a large amount of organic solvent is required to be used, and the environment is not friendly; in the case of (2), after the adsorption, the desorption process using an acid is required, and the operation is complicated. The membrane separation method has the advantages that the membrane separation method is environment-friendly and continuous in operability, only solution needs to be replaced, the membrane does not need to be further treated in the separation process, and the membrane separation method is simple and convenient to operate.
Wherein the electrodialysis separation of the invention is carried out by a system comprising a self-polymerization microporous polymer membrane, the system comprising a power supply and sequentially arranged cathodesPolar plate, electrodialysis membrane group, anode plate; the electrodialysis membrane group comprises an anion exchange membrane, a polymer membrane with micropores and an anion exchange membrane which are sequentially arranged; a cathode chamber is formed between the cathode plate and the adjacent anion exchange membrane, and an anode chamber is formed between the anode plate and the adjacent anion exchange membrane; two poles of the power supply are respectively connected with the cathode plate and the anode plate; supplying an electrode solution to the cathode and anode compartments, supplying a solution containing a metal salt to the system 6 Li + Ions and 7 Li + an ionic electrolyte solution.
The electrodialysis system comprises a conventional power supply; for the cathode plate, the electrodialysis membrane group and the anode plate which are arranged in sequence, the electrodialysis membrane group can be formed by arranging commercial anion exchange membranes, lithium isotopes are separated from the microporous polymer membranes and the commercial anion exchange membranes in sequence. A cathode chamber is arranged between the cathode plate and the adjacent anion exchange membrane, and an anode chamber is arranged between the anode plate and the adjacent anion exchange membrane; and connecting the negative end of the power supply to the negative plate, and connecting the positive end of the power supply to the positive plate. The system also includes a depleting compartment (i.e., providing the initial feed liquid to be separated) and a concentrating compartment (i.e., receiving side, containing the separated feed liquid); the electrode solution can be circularly supplied to the cathode chamber and the anode chamber; circulating supply of the liquid containing substance into the desalination chamber 6 Li + Ions and 7 Li + an ionic electrolyte solution, with water (typically deionized water) being circulated into the concentrating compartments.
In the present invention, the anion exchange membranes may be all commercial membranes AMX (Astom co., ltd).
In the present invention, the electrode solution introduced into the cathode chamber and the anode chamber is not required to be electrolyzed at the electrodes in principle, and specifically, 0.2 to 0.5 mol. L -1 The solution of sodium sulfate, sodium nitrate, potassium sulfate, potassium nitrate or the like is preferably 0.3 mol/L -1 Sodium sulfate solution.
In the embodiment of the invention, the feed liquid in the desalting chamber is 6 Li + Ions and 7 Li + an ionic mixed electrolyte solution. The electrolyte solution is prepared in a laboratory 6 Li + 、 7 Li + When the ions are mixed with the solution, the ion-exchange membrane is used, 6 Li + 、 7 Li + the molar ratio is 1: 1, the solution is prepared from 1000ppm 6 Li + The standard solution is prepared with 1000ppm of lithium nitrate solution with the concentration of 0.083mo1.L -1 。
The electrolyte solution 6 Li + 、 7 Li + When the ions are in natural abundance ratio, the solution concentration is 0.1 mol.L -1 The electrolyte may be one or more of lithium nitrate, lithium chloride, lithium bromide, lithium iodide, lithium carbonate, lithium sulfate, lithium chlorate, lithium perchlorate, and lithium hydroxide.
In a specific embodiment of the invention, the deionized water has a conductivity of less than 2 μ S-cm -1 。
In a specific embodiment of the invention, the electrodialysis is maintained in a constant current mode; the current density was maintained at 0.5mA cm -2 ，1mA·cm -2 ，2mA·cm -2 In one of the above-mentioned processes, 6 Li +/7 Li + the separation selectivity of (a) increases with decreasing current density.
In summary, the invention discloses a self-microporous polymer membrane for lithium isotope separation, a preparation method thereof and an electrodialysis separation application. The lithium isotope separation membrane is a crown ether main chain type self-provided microporous polymer membrane, and the preparation method comprises the following steps: the dibenzocrown ether is used as a monomer, and is subjected to nitration and hydrogenation reduction to obtain 2,6-diamino-dibenzocrown ether; passing the resulting diamine monomer through
Base polymerization is carried out to prepare a crown ether main chain type self-possessed microporous polymer; the obtained polymer is prepared into the polymer membrane with micropores by a solvent volatilization method. The electrodialysis is based on a system comprising a power supply, and a cathode plate, an electrodialysis membrane group and an anode plate which are sequentially arranged; wherein the electrodialysis membrane group consists of a commercial anion exchange membrane-the self-microporous polymer membrane-a commercial anion exchange membrane which are arranged in sequence. The invention prepares a crown ether main chain type self-polymerization microporous polymer and a film for lithium isotope separation, which 6 Li + / 7 Li + The selective separation performance is excellent, the single-stage selectivity is 1.16, the membrane preparation process is simple and controllable, the separation process can be continuous, and the selective separation method has the advantages of environmental friendliness, energy conservation, high efficiency and the like.
In order to better understand the technical content of the invention, specific examples are provided below to further illustrate the invention.
Example 1
The preparation of the polymer film with self-micropore for lithium isotope based on dibenzo-15-crown-5-ether comprises the preparation and film preparation of the polymer, and the synthetic route of the polymer is as follows:
(1) 0.50g of dibenzo-15-crown-5-ether was weighed into a 50mL round-bottom flask, dissolved by adding 10mL of chloroform, followed by dropwise addition of 9mL of acetic acid, followed by stirring for 5min after the completion of the dropwise addition, followed by dropwise addition of 0.3mL of nitric acid, followed by stirring for 1h after the completion of the dropwise addition, followed by warming to 70 ℃ and reacting overnight. Then decompressing and evaporating the reaction liquid to dryness, adding methylene dichloride for redissolving, washing for 2-3 times, drying overnight by using anhydrous sodium sulfate, filtering, decompressing and evaporating filtrate to dryness to obtain 2,6-dinitro-dibenzo-15-crown-5-ether.
(2) Weighing 0.59g of 2,6-dinitro-dibenzo-15-crown-5-ether into a 50mL round bottom flask, adding 18mL of ethanol, then adding 138mg of palladium-carbon catalyst and 5.23g of hydrazine hydrate, heating to 90 ℃ under the protection of nitrogen atmosphere for refluxing, reacting overnight, filtering the reaction solution while hot, and evaporating the obtained filtrate under reduced pressure to dryness to obtain 2,6-diamino-dibenzo-15-crown-5-ether.
(3) Weighing 0.40g of 2,6-diamino-dibenzo-15-crown-5-ether into a 5mL round bottom flask, adding 0.44g of dimethoxymethane, dropwise adding 4mL of trifluoroacetic acid in an ice water bath under the protection of nitrogen, reacting for 48h, slowly pouring the reaction liquid into ammonia water to precipitate the polymer, detecting to obtain the compound with the structure (PIM-DB 15C 5-TB) shown as the formula 1, washing with water, and drying. FIG. 1 is a nuclear magnetic hydrogen spectrum of PIM-DB15C5-TB prepared in example 1.
(4) 0.25g of PIM-DB15C5-TB polymer is weighed and dissolved by using 20mL of chloroform, and then the polymer solution is transferred to a glass culture dish, and the solvent is evaporated and evaporated under normal temperature and pressure to obtain the self-contained microporous polymer membrane for lithium isotope separation. A glass petri dish with a diameter of 6.5cm was used as the coating material, and the thickness of the lithium isotope separation membrane was 60 to 80 μm.
The following is a characterization of dibenzo-15-crown-5-ether-based self-microporous polymer membranes for lithium isotope separation:
(1) Contact Angle testing
And separating the prepared lithium isotope from the microporous polymer film, drying in an oven, and taking a flat film sample for static contact angle measurement. Measurement was performed by the pendant drop method using deionized water at room temperature; after placing a water drop on the surface of the membrane in the air with a micro syringe, and leaving it to stand for 5 seconds, an image of the water drop was recorded, and the water contact angle was measured from the recorded image, and the result was shown in fig. 2, which is 72.48 °, indicating that the PIM-DB15C5-TB membrane is hydrophilic.
(2) BET Nitrogen adsorption/desorption test
The prepared polymer with micropores is dried under vacuum for 24h, about 0.1g is weighed into a test glass tube, and BET nitrogen adsorption and desorption test is carried out, and the obtained nitrogen adsorption and desorption curve is shown in figure 3. According to FIG. 3, the BET multipoint specific surface area is 38.28m 2 The result is that the polymer with micropores has a certain amount of micropores and has channels for ion transmission.
(3) Room temperature stress strain test
The prepared polymer film with micropores is dried under vacuum for 24h, and a sample of 1 × 4cm is cut out to be subjected to a room temperature stress strain test, and the obtained result is shown in fig. 4. According to fig. 4, it remains stable at an applied stress of 26.5MPa, indicating that the film has good mechanical properties.
Example 2
Dibenzo-15-crown-5-ether-based Li for lithium isotope separation from microporous polymer membranes + Ion penetration test
1. A self-microporous polymer membrane for lithium isotope separation based on dibenzo-15-crown-5-ether was prepared as in example 1 and subjected to the relevant characterization.
2. Soaking a lithium isotope separation membrane PIM-DB15C5-TB to be tested in deionized water overnight, placing the membrane in a penetration device (shown in figure 5), wherein the physical and chemical properties of the front and back surfaces of the PIM-DB15C5-TB membrane are the same, and adding 0.1 mol.L on the penetration side -1 Lithium nitrate (LiNO) 3 ) Adding equal volume of deionized water to the receiving side of the solution, wherein the initial conductivity of the deionized water is less than 2 mu S-cm -1 The conductivity on the receiving side is monitored using a conductivity meter, and the measured conductivity is converted to concentration according to a standard curve. The results are shown in FIG. 6, which indicates that the PIM-DB15C5-TB film has superior Li + Ion conductivity.
Example 3
Of polymeric membranes with micropores for lithium isotope separation based on dibenzo-15-crown-5-ether 6 Li + / 7 Li + Separation test
1. A self-microporous polymer membrane for lithium isotope separation based on dibenzo-15-crown-5-ether was prepared as in example 1 and subjected to the relevant characterization.
2. Of laboratory systems 6 Li + / 7 Li + 1: 1 feed liquid separation test
(1) Using commercially available 1000ppm 6 Li + Standard solution prepared with 1000ppm lithium nitrate solution prepared in laboratory 6 Li + / 7 Li + The concentration of the mixed solution is 0.083m01. L with the molar ratio of 1: 1 -1 。
(2) Soaking lithium isotope separation membrane PIM-DB15C5-TB to be tested in deionized water overnight, placing the membrane in a permeation device (shown in figure 5), and adding the prepared solution to the permeation side 6 Li + / 7 Li + The mixed solution is 1: 1, the receiving side is added with the same volume of deionized water, and the initial conductivity of the deionized water is lower than 2 mu S-cm -1 . The solution on the receiving side was detected by inductively coupled plasma mass spectrometry (ICP-MS), and the results are shown in FIG. 7, based on dibenzo-15-crown-5-etherLithium isotope separation membrane pair 6 Li、 7 As a result of static diffusion of the 1: 1 mixed solution of Li, the optimum selectivity was 1.08.
(3) As shown in fig. 8, an electrodialysis device is constructed, and the electrodialysis system comprises a power supply, and a cathode plate, an electrodialysis membrane group and an anode plate which are arranged in sequence; the electrodialysis membrane group is formed by sequentially arranging anion exchange membranes AMX-lithium isotopes separated from microporous polymer membranes-anion exchange membranes AMX. A cathode chamber (cathode-end polarization chamber) is formed between the cathode plate and the adjacent anion exchange membrane, and an anode chamber (anode-end polarization chamber) is formed between the anode plate and the adjacent anion exchange membrane; connecting the negative end of the power supply to the negative plate and the positive end of the power supply to the positive plate; 0.3mol-L is circularly supplied to the cathode chamber and the anode chamber -1 Sodium sulfate solution, and supplying the solution to desalting chamber (providing initial feed chamber before separation) 6 Li + 、 7 Li + Electrolyte solution with 1: 1 mixed ions, and deionized water with initial conductivity lower than 2 μ S-cm is supplied to the concentrating chamber (for receiving separated material liquid) -1 。
The electrodialysis adopts a constant current mode, and the working current density is 2 mA-cm in sequence -2 ，1mA·cm -2 ，0.5mA·cm -2 . The solution in the concentration chamber was sampled and detected by inductively coupled plasma mass spectrometry (ICP-MS), and the results are shown in FIG. 9, for a 1: 1 ratio of a dibenzo-15-crown-5-ether based lithium isotope separation membrane PIM-DB15C5-TB 6 Li + 、 7 Li + The optimum selectivity of the electrodialysis separation result of the mixed solution is 1.12, 6 Li +/7 Li + the separation selectivity of (a) increases with decreasing current density.
Example 4
1. A self-microporous polymer membrane for lithium isotope separation based on dibenzo-15-crown-5-ether was prepared as in example 1 and subjected to the relevant characterization.
2. Actual System (0.1 mol. L) -1 Lithium nitrate) feed solution 6 Li +/7 Li + Separation test
(1) Preparation 0.1mol·L -1 The lithium nitrate solution of (1).
(2) Soaking the lithium isotope separation membrane PIM-DB15C5-TB to be tested in deionized water overnight, placing the membrane in a permeation device (shown in figure 5), and adding 0.1 mol.L on the permeation side -1 The receiving side is added with equal volume of deionized water, and the initial conductivity of the deionized water is lower than 2 mu S-cm -1 . The solution on the receiving side was detected by inductively coupled plasma mass spectrometry (ICP-MS), and as a result, as shown in fig. 10, lithium isotopes based on dibenzo-15-crown-5-ether were separated from the polymer film having micropores, and the solution on the receiving side was analyzed by ICP-MS 6 Li+、 7 Li + The separation selectivity was 1.06 as a result of the static diffusion separation of the actual system.
(3) As shown in fig. 8, an electrodialysis device is constructed, and the electrodialysis system comprises a power supply, and a cathode plate, an electrodialysis membrane group and an anode plate which are arranged in sequence; the electrodialysis membrane group is an anion exchange membrane, a lithium isotope separation self-contained microporous polymer membrane and an anion exchange membrane which are sequentially arranged. A cathode chamber is formed between the cathode plate and the adjacent anion exchange membrane, and an anode chamber is formed between the anode plate and the adjacent anion exchange membrane; connecting the negative electrode end of the power supply to the negative plate, and connecting the positive electrode end of the power supply to the positive plate; electrode solution is circularly supplied to the cathode chamber and the anode chamber, and 0.1 mol.L is circularly supplied to the desalting chamber -1 Is circulated to the concentration chamber with deionized water having an initial conductivity of less than 2 μ S-cm -1 . The electrodialysis adopts a constant current mode, and the working current density is 2 mA-cm in sequence -2 ，1mA·cm -2 ，0.5mA·cm -2 . The solution in the concentration chamber was sampled and detected by inductively coupled plasma mass spectrometry (ICP-MS), and as a result, as shown in fig. 11, the optimum selectivity of the electrodialytic separation of lithium isotopes based on dibenzo-15-crown-5-ether from the actual system with microporous polymer membranes was 1.16.
The separation of a laboratory system from an actual system can be regarded as a separate example of different concentrations; the difference is that the laboratory system 6 Li + / 7 Li + 1: 1, can be more conveniently embodiedMembrane intrinsic separation selectivity; practical systems (i.e. ordinary lithium salt solutions, simulating natural abundance ratios) 6 Li + / 7 Li + ) The membrane shows the separation performance when the membrane is used for separating actual solution (such as seawater).
According to the embodiments, the polymerization reaction directly takes the crown ether as the main chain, and an ion transmission channel is constructed, so that the prepared crown ether main chain type self-micropore polymer membrane has excellent ion selective separation performance, higher ion flux and is beneficial to membrane separation of lithium isotopes; the film making process has simple and controllable steps and high efficiency.
On the basis, the invention combines the polymer membrane with self micropores with an electrodialysis membrane separation process for lithium isotope separation. The electrodialysis is based on a system comprising a power supply, and a cathode plate, an electrodialysis membrane group and an anode plate which are sequentially arranged; wherein, the electrodialysis membrane group can be composed of a commercial anion exchange membrane-the self-microporous polymer membrane-a commercial anion exchange membrane which are arranged in sequence. The invention combines the polymer membrane with micropores with electrodialysis to separate lithium isotope, and the crown ether pair is based on 6 Li + 、 7 Li + Under the driving action of an external electric field, 6 Li + has an electrical mobility greater than 7 Li + And the two have synergistic effect, so that the separation efficiency of the lithium isotope is effectively improved. In the embodiment of the present invention, it is, 6 Li + / 7 Li + the selective separation performance is excellent, and the single-stage selectivity is 1.16. The method for separating the lithium isotopes has the characteristics of safety, environmental protection, continuous and stable separation process, energy conservation, high efficiency and the like.
The above embodiments are described herein only to aid in the understanding of the method of the present invention and its core ideas. It should be noted that, for those skilled in the art, it is possible to make various improvements and modifications to the present invention without departing from the principle of the present invention, and those improvements and modifications also fall within the scope of the claims of the present invention.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A self-contained microporous polymer membrane for lithium isotope separation is characterized by being prepared from a crown ether main chain type polymer, wherein the crown ether main chain type polymer has a structure shown in a formula 1, and n is the polymerization degree;
2. the self-contained microporous polymer membrane according to claim 1, wherein the self-contained microporous polymer membrane is hydrophilic.
3. A method of making a self-contained microporous polymer membrane according to any of claims 1-2, comprising the steps of:
s1, passing 2,6-diamino-dibenzo-15-crown-5-ether through
Base polymerization to obtain a crown ether main chain type polymer shown as a formula 1; the 2,6-diamino-dibenzo-15-crown-5-ether structure is shown as formula 2;
s2, dissolving the crown ether main chain type polymer by using a solvent, and then volatilizing the solvent to obtain the polymer film with the micropores;
4. the method for preparing a polymer membrane with self-micropores according to claim 3, wherein in step S1, the 2,6-diamino-dibenzo-15-crown-5-ether represented by formula 2 is obtained as follows:
using dibenzo-15-crown-5-ether as a monomer, chloroform as a reaction solvent and acetic acid as a dehydrating agent, and nitrifying the monomer by using nitric acid to obtain 2,6-dinitro-dibenzo-15-crown-5-ether;
and reducing the obtained 2,6-dinitro-dibenzo-15-crown-5-ether by using hydrazine hydrate in a protective atmosphere by using ethanol as a reaction solvent to obtain the 2,6-diamino-dibenzo-15-crown-5-ether.
5. The method of claim 3, wherein in step S1, the microporous polymer membrane is prepared
The Base polymerization is specifically as follows: reacting 2,6-diamino-dibenzo-15-crown-5-ether with dimethoxymethane for a certain time by using trifluoroacetic acid as a reaction solvent to obtain the crown ether main chain type polymer shown in the formula 1.
6. The method according to claim 3, wherein in step S2, the solvent used for dissolving the crown ether main chain type polymer is chloroform, the mass concentration of the obtained solution is 1-2 wt.%, and the solvent is volatilized at room temperature to obtain the polymer membrane with micropores.
7. Separation of a self-supporting microporous polymer membrane as claimed in any of claims 1 to 2 6 Li and 7 application in Li isotopes.
8. Separation of polymer membranes with self-micropores according to any of claims 1 to 2 in combination with electrodialysis 6 Li and 7 application in Li isotopes.
9. The use of claim 8, wherein the electrodialysis separation is performed using a system comprising a self-polymerized microporous polymer membrane, the system comprising a power source and a cathode plate, an electrodialysis membrane set, an anode plate arranged in sequence; the electrodialysis membrane group comprises an anion exchange membrane, a polymer membrane with micropores and an anion exchange membrane which are sequentially arranged; a cathode chamber is formed between the cathode plate and the adjacent anion exchange membrane, and an anode chamber is formed between the anode plate and the adjacent anion exchange membrane; two poles of the power supply are respectively connected with the cathode plate and the anode plate; supplying an electrode solution to the cathode and anode compartments, supplying a solution containing a metal salt to the system 6 Li + ion and 7 electrolyte solution of Li + ions.
10. The use according to claim 9, characterized in that the electrode solution introduced in the cathode and anode chambers is a sodium sulphate solution; the electrolyte is one or more of lithium nitrate, lithium chloride, lithium bromide, lithium iodide, lithium carbonate, lithium sulfate, lithium chlorate, lithium perchlorate and lithium hydroxide.
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