WO2022239864A1 - リチウム回収装置およびリチウム回収方法 - Google Patents
リチウム回収装置およびリチウム回収方法 Download PDFInfo
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- WO2022239864A1 WO2022239864A1 PCT/JP2022/020226 JP2022020226W WO2022239864A1 WO 2022239864 A1 WO2022239864 A1 WO 2022239864A1 JP 2022020226 W JP2022020226 W JP 2022020226W WO 2022239864 A1 WO2022239864 A1 WO 2022239864A1
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- electrolyte membrane
- aqueous solution
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- 238000011084 recovery Methods 0.000 title claims abstract description 174
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 102
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 101
- 238000000034 method Methods 0.000 title claims description 40
- 239000007864 aqueous solution Substances 0.000 claims abstract description 175
- 239000003792 electrolyte Substances 0.000 claims abstract description 159
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 45
- 238000012545 processing Methods 0.000 claims abstract description 13
- 239000012528 membrane Substances 0.000 claims description 156
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 43
- 150000002500 ions Chemical class 0.000 claims description 16
- 238000010438 heat treatment Methods 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 11
- 230000009467 reduction Effects 0.000 claims description 8
- 229910052751 metal Inorganic materials 0.000 claims description 3
- 239000002184 metal Substances 0.000 claims description 3
- 238000000638 solvent extraction Methods 0.000 claims description 3
- 229910021645 metal ion Inorganic materials 0.000 abstract description 20
- 238000006243 chemical reaction Methods 0.000 description 57
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 description 40
- 239000003014 ion exchange membrane Substances 0.000 description 21
- 150000001768 cations Chemical class 0.000 description 13
- 239000013535 sea water Substances 0.000 description 13
- 238000012546 transfer Methods 0.000 description 13
- 239000000460 chlorine Substances 0.000 description 12
- 230000007423 decrease Effects 0.000 description 11
- 239000002994 raw material Substances 0.000 description 11
- 230000007547 defect Effects 0.000 description 10
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 10
- 238000000909 electrodialysis Methods 0.000 description 9
- 238000012986 modification Methods 0.000 description 9
- 230000004048 modification Effects 0.000 description 9
- 239000007788 liquid Substances 0.000 description 8
- 150000001450 anions Chemical class 0.000 description 7
- 239000000243 solution Substances 0.000 description 7
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 6
- 230000003197 catalytic effect Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 6
- 238000002474 experimental method Methods 0.000 description 6
- 239000011734 sodium Substances 0.000 description 6
- 230000005684 electric field Effects 0.000 description 5
- 239000007772 electrode material Substances 0.000 description 5
- 238000005192 partition Methods 0.000 description 5
- 239000010936 titanium Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 229910052760 oxygen Inorganic materials 0.000 description 4
- 239000005279 LLTO - Lithium Lanthanum Titanium Oxide Substances 0.000 description 3
- -1 hydroxide ions Chemical class 0.000 description 3
- 238000013508 migration Methods 0.000 description 3
- 230000005012 migration Effects 0.000 description 3
- 239000012466 permeate Substances 0.000 description 3
- 229910052719 titanium Inorganic materials 0.000 description 3
- NAWXUBYGYWOOIX-SFHVURJKSA-N (2s)-2-[[4-[2-(2,4-diaminoquinazolin-6-yl)ethyl]benzoyl]amino]-4-methylidenepentanedioic acid Chemical compound C1=CC2=NC(N)=NC(N)=C2C=C1CCC1=CC=C(C(=O)N[C@@H](CC(=C)C(O)=O)C(O)=O)C=C1 NAWXUBYGYWOOIX-SFHVURJKSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 2
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 description 2
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 2
- 238000009835 boiling Methods 0.000 description 2
- 229910052801 chlorine Inorganic materials 0.000 description 2
- 239000010949 copper Substances 0.000 description 2
- 230000007797 corrosion Effects 0.000 description 2
- 238000005260 corrosion Methods 0.000 description 2
- 238000007710 freezing Methods 0.000 description 2
- 230000008014 freezing Effects 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 2
- 238000007654 immersion Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 description 2
- 239000001301 oxygen Substances 0.000 description 2
- 229910052697 platinum Inorganic materials 0.000 description 2
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 235000008694 Humulus lupulus Nutrition 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- NIXOWILDQLNWCW-UHFFFAOYSA-N acrylic acid group Chemical group C(C=C)(=O)O NIXOWILDQLNWCW-UHFFFAOYSA-N 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005341 cation exchange Methods 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910021525 ceramic electrolyte Inorganic materials 0.000 description 1
- 238000000262 chemical ionisation mass spectrometry Methods 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 239000000428 dust Substances 0.000 description 1
- 238000003411 electrode reaction Methods 0.000 description 1
- 238000005868 electrolysis reaction Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
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- 230000004927 fusion Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 230000001771 impaired effect Effects 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- 238000005372 isotope separation Methods 0.000 description 1
- CEMTZIYRXLSOGI-UHFFFAOYSA-N lithium lanthanum(3+) oxygen(2-) titanium(4+) Chemical compound [Li+].[O--].[O--].[O--].[O--].[Ti+4].[La+3] CEMTZIYRXLSOGI-UHFFFAOYSA-N 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
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- 150000002739 metals Chemical class 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000035515 penetration Effects 0.000 description 1
- CLSUSRZJUQMOHH-UHFFFAOYSA-L platinum dichloride Chemical compound Cl[Pt]Cl CLSUSRZJUQMOHH-UHFFFAOYSA-L 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
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- 238000001179 sorption measurement Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910001428 transition metal ion Inorganic materials 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/14—Alkali metal compounds
- C25B1/16—Hydroxides
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
- C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B1/00—Electrolytic production of inorganic compounds or non-metals
- C25B1/01—Products
- C25B1/34—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis
- C25B1/46—Simultaneous production of alkali metal hydroxides and chlorine, oxyacids or salts of chlorine, e.g. by chlor-alkali electrolysis in diaphragm cells
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B15/00—Operating or servicing cells
- C25B15/02—Process control or regulation
- C25B15/023—Measuring, analysing or testing during electrolytic production
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B15/00—Operating or servicing cells
- C25B15/08—Supplying or removing reactants or electrolytes; Regeneration of electrolytes
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
- C25B9/00—Cells or assemblies of cells; Constructional parts of cells; Assemblies of constructional parts, e.g. electrode-diaphragm assemblies; Process-related cell features
- C25B9/17—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof
- C25B9/19—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms
- C25B9/21—Cells comprising dimensionally-stable non-movable electrodes; Assemblies of constructional parts thereof with diaphragms two or more diaphragms
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/42—Electrodialysis; Electro-osmosis ; Electro-ultrafiltration; Membrane capacitive deionization
- B01D61/422—Electrodialysis
Definitions
- the present invention relates to a lithium recovery device and a lithium recovery method for selectively recovering lithium ions from an aqueous solution.
- Lithium (Li) is a resource in high demand as a raw material for lithium-ion secondary batteries, fuel for nuclear fusion reactors, and the like, and a stable supply and cheaper extraction method is required.
- a stable supply source of Li there is, for example, seawater dissolved in the form of cations Li + .
- the positive electrode of a lithium ion secondary battery mainly contains Li in the form of lithium cobaltate (LiCoO 2 ) or the like, an inexpensive recovery technique from batteries discarded due to the end of battery life is expected.
- Patent Document 1 Non-Patent Document 1
- the lithium recovery apparatus 100 divides the processing tank 1 into a supply tank 11 and a recovery tank 12 with a lithium ion conductive electrolyte membrane (hereinafter referred to as an electrolyte membrane) 2, and an electrode 131 in the supply tank 11 and an electrode 132 in the recovery tank 12.
- a power source 151 is connected between and with the electrode 131 being the positive electrode.
- a Li-containing aqueous solution SW such as seawater is put into the supply tank 11 as a Li source, and a Li recovery aqueous solution AS such as pure water is put into the recovery tank 12 .
- the reaction of the following formula (1) occurs in the vicinity of the electrode 131 in the Li-containing aqueous solution SW of the supply tank 11, oxygen (O 2 ) is generated, and water, which is an anion, is generated. Since the oxide ions (OH ⁇ ) are reduced, the reaction of the following formula (2) occurs in which Li + in the Li-containing aqueous solution FS moves into the electrolyte membrane 2 in order to maintain the charge balance.
- the reaction of the following formula (3) occurs in the vicinity of the electrode 132 to generate hydrogen (H 2 ) and increase OH ⁇ .
- a reaction of the following formula (4) is caused in which Li + moves to the Li recovery aqueous solution AS.
- Li + contained in the electrolyte membrane 2 (electrolyte) is expressed as Li + (electrolyte).
- Li + from the Li-containing aqueous solution SW permeates the electrolyte membrane 2 to Li Move to the recovery aqueous solution AS.
- Li + is selectively transferred from the Li-containing aqueous solution SW to the Li recovery aqueous solution AS, and an aqueous Li + aqueous solution (lithium hydroxide (LiOH) aqueous solution) is obtained in the recovery tank 12 .
- Li + aqueous solution lithium hydroxide (LiOH) aqueous solution
- the reaction of formulas (1) and (3) increases as the amount of electrons e ⁇ transferred per time from the Li-containing aqueous solution SW to the electrode 131 and from the electrode 132 to the Li-recovering aqueous solution AS increases. becomes faster, and the amount of movement of Li + per time also increases.
- the electrodes 131 and 132 are preferably provided in contact with the electrolyte membrane 2 (Patent Document 1). It has a porous structure such as a mesh so as to be in contact with the electrolyte membrane 2 .
- the present inventors did not apply a voltage for electrodialysis from both sides of the electrolyte membrane, but formed a circuit with electrodes spaced apart from the electrolyte membrane.
- a technique for suppressing the potential difference between both surfaces of a membrane Patent Document 2.
- the lithium recovery apparatus 100A includes an electrode 133 separated from the electrolyte membrane 2 in the recovery tank 12, and the electrode 133 is attached to the surface of the electrolyte membrane 2 on the supply tank 11 side. They are paired and connected to power supply 105 .
- the power source 105 may be two power sources connected in series, and the power source on the positive electrode side may be connected between the electrodes 131 and 132 attached to both sides of the electrolyte membrane 2 .
- the present invention has been made in view of the above problems, and an object of the present invention is to provide a lithium recovery method and a lithium recovery apparatus using an electrodialysis method with high selectivity and high productivity.
- the inventors of the present invention formed a circuit with electrodes having a lower potential on the negative electrode side and spaced apart from the electrolyte membrane so that the electrolyte membrane would not exhibit electronic conductivity even if the potential difference between the two surfaces was large. I figured it out.
- the lithium recovery apparatus includes a treatment tank partitioned into a first tank and a second tank, and the water or aqueous solution contained in the second tank contains the lithium ions contained in the first tank. It is a device for transferring lithium ions from an aqueous solution.
- the lithium recovery apparatus according to the present invention comprises: a lithium ion conductive electrolyte membrane partitioning the processing tank; porous electrodes provided in contact with both surfaces of the lithium ion conductive electrolyte membrane; A sub-electrode provided in the two tanks and spaced apart from the electrode of the porous structure and the lithium ion conductive electrolyte membrane, and between the electrodes of the porous structure, the side of the first tank as a positive electrode.
- the battery When the battery is on, the current does not flow to the electrode of the porous structure on the side of the second tank or flows from the positive electrode of the second power supply.
- the lithium recovery method in a processing tank partitioned into a first tank and a second tank by a lithium ion conductive electrolyte membrane, It is a method of transferring lithium ions from an aqueous solution containing lithium ions.
- the first tank side is connected as a positive electrode between electrodes of a porous structure provided in contact with both surfaces of the lithium ion conductive electrolyte membrane.
- a first power supply and a second power supply connected in series to the negative electrode of the first power supply and connected to a sub-electrode provided with the negative electrode spaced apart from the lithium ion conductive electrolyte membrane are connected to the second tank side.
- a voltage is applied such that current does not flow through the electrodes of the porous structure provided in the , or flows from the positive electrode of the second power supply.
- lithium can be recovered selectively and at high speed even from an aqueous solution, such as seawater, in which lithium has an extremely low concentration and coexists with other metal ions, thereby improving productivity. can be improved, and the energy efficiency is less likely to decrease.
- FIG. 1 is a schematic diagram illustrating the configuration of a lithium recovery device according to an embodiment of the present invention
- FIG. FIG. 2 is a schematic diagram of the lithium recovery device shown in FIG. 1 for explaining the lithium recovery method according to the embodiment of the present invention
- FIG. 2 is a circuit diagram of the lithium recovery device shown in FIG. 1, explaining the lithium recovery method according to the embodiment of the present invention
- FIG. 5 is a schematic diagram illustrating the configuration of a lithium recovery device and a lithium recovery method according to a modification of the embodiment of the present invention
- 4 is a graph showing the dependence of the amount of lithium transferred per time on the applied voltage between both surfaces of the lithium ion conductive electrolyte membrane in Examples.
- 4 is a graph showing the dependence of the amount of lithium transferred per time and the current in Examples on the applied voltage between the surface of the lithium ion conductive electrolyte membrane and the sub-electrode on the second tank side.
- 4 is a graph showing input power dependence of the amount of lithium transferred per hour in an example.
- 4 is a graph showing the total voltage dependence of the energy efficiency of lithium transfer in Examples.
- 4 is a graph showing the input power dependence of the energy efficiency of lithium transfer in Examples.
- 4 is a graph showing the temperature dependence of the amount of lithium transferred per hour in Examples.
- 1 is a schematic diagram of a lithium recovery device for explaining a conventional lithium recovery method using an electrodialysis method;
- FIG. 1 is a schematic diagram of a lithium recovery device for explaining a conventional lithium recovery method using an electrodialysis method;
- FIG. 1 is a schematic diagram of a lithium recovery device for explaining a conventional lithium recovery method using an electrodialysis method;
- FIG. 1 is a schematic diagram of a
- the lithium recovery apparatus 10 includes a treatment tank 1, an electrolyte membrane (lithium ion conductive electrolyte membrane) 2 partitioning the treatment tank 1, and each surface of the electrolyte membrane 2 coated with It comprises a first electrode 31 and a second electrode 32 , a third electrode (sub-electrode) 33 , a first power source 51 and a second power source 52 connected in series, a heating device 6 and a circulation device (circulation means) 7 .
- a treatment tank 1 an electrolyte membrane (lithium ion conductive electrolyte membrane) 2 partitioning the treatment tank 1, and each surface of the electrolyte membrane 2 coated with It comprises a first electrode 31 and a second electrode 32 , a third electrode (sub-electrode) 33 , a first power source 51 and a second power source 52 connected in series, a heating device 6 and a circulation device (circulation means) 7 .
- the treatment tank 1 consists of a supply tank (first tank) 11 containing a Li-containing aqueous solution SW such as seawater and a recovery tank (second tank) 12 containing a Li-recovering aqueous solution AS via an electrolyte membrane 2. divided into two.
- the third electrode 33 is provided in the recovery tank 12 so as to be separated from the electrolyte membrane 2 .
- the first power supply 51 has a positive (+) pole connected to the first electrode 31 and a negative (-) pole connected to the second electrode 32 .
- the second power supply 52 is connected in series with the negative pole of the first power supply 51 , that is, the positive pole is connected to the second electrode 32 and the negative pole is connected to the third electrode 33 .
- the lithium recovery device 10 according to the present embodiment is different from the conventional lithium recovery device (for example, the lithium recovery device 100 shown in FIG. 10) using the electrodialysis method. It is a configuration in which a second power source 52 connected in series to the negative electrode and a third electrode 33 connected to the negative electrode are added. Each element constituting the lithium recovery apparatus according to the embodiment of the present invention will be described below.
- the treatment tank 1 is made of a material that does not deteriorate such as corrosion even when it comes into contact with the Li-containing aqueous solution SW and the Li-recovery aqueous solution AS including the Li-recovered aqueous solution (for example, lithium hydroxide (LiOH) aqueous solution).
- the processing tank 1 may have a volume corresponding to the required processing capacity, and its shape and the like are not particularly limited.
- the electrolyte membrane 2 is an electrolyte that has lithium ion conductivity, does not conduct metal ions M n + other than Li + contained in the Li-containing aqueous solution SW, and preferably does not conduct electrons e ⁇ .
- Metal ions M n + other than Li + are, for example, Na + , Mg 2+ , Ca 2+ and the like when the Li-containing aqueous solution SW is seawater.
- a ceramic electrolyte having these properties is more preferable. Specifically, lithium-lanthanum-titanium oxide (La 2/3-x Li 3x TiO 3 , also called LLTO) and the like can be mentioned.
- Such an electrolyte membrane 2 has lattice defects at a certain rate, and since the size of the lattice defect sites and the narrowest region (bottleneck) in the ion migration path are small, metal ions larger in diameter than Li + not conduct.
- the first electrode 31 and the second electrode 32 are paired to apply a voltage across both surfaces of the electrolyte membrane 2 , and the first electrode 31 is in contact with the surface of the electrolyte membrane 2 on the supply tank 11 side.
- the second electrode 32 is provided in contact with the surface of the electrolyte membrane 2 on the recovery tank 12 side.
- the first electrode 31 is also paired with a third electrode 33, which will be described later, to apply a voltage.
- the first electrode 31 and the second electrode 32 apply a voltage to a wide range of the electrolyte membrane 2, while the Li-containing aqueous solution SW or the Li-recovering aqueous solution AS contacts a sufficient area of the surface of the electrolyte membrane 2. , has a network-like porous structure.
- the first electrode 31 has catalytic activity and electronic conductivity for the reaction of the following formula (1) and the reaction of the following formula (2), and is formed of an electrode material that is stable even when a voltage is applied in the Li-containing aqueous solution SW. Furthermore, it is preferable to use a material that can be easily processed into the above shape.
- the second electrode 32 has catalytic activity and electronic conductivity for the reaction of the following formula (1) and the reaction of the following formula (4), and is stable even when a voltage is applied in the Li recovery aqueous solution AS including after Li recovery. It is preferable that the electrodes are made of an electrode material that is suitable for use, and that the material can be easily processed into the shape described above.
- the first electrode 31 and the second electrode 32 are preferably made of, for example, platinum (Pt) as such an electrode material.
- the following formula (2) represents a reaction in which Li + in the aqueous solution (Li-containing aqueous solution SW) moves into the electrolyte membrane 2 .
- the following formula (4) represents a reaction in which Li + in the electrolyte membrane 2 moves to an aqueous solution (aqueous solution AS for recovering Li).
- the third electrode 33 is an electrode for forming a potential lower than that of the surface of the electrolyte membrane 2 in the Li recovery aqueous solution AS. Therefore, the third electrode 33 is preferably arranged in the recovery tank 12 so as not to contact the electrolyte membrane 2 and the second electrode 32 and arranged parallel to the second electrode 32 . Furthermore, in order to keep the voltage V2 of the second power supply 52 small, it is preferable that the third electrode 33 be arranged close to the second electrode 32 to the extent that short-circuiting does not occur, as will be described later. Moreover, the third electrode 33 preferably has a shape such as a mesh shape so as to increase the contact area with the Li recovery aqueous solution AS.
- the third electrode 33 has catalytic activity and electronic conductivity for the reaction of the following formula (3), and is formed of an electrode material that is stable even when a voltage is applied in the Li recovery aqueous solution AS including after Li recovery. Platinum (Pt) is preferred.
- the third electrode 33 can be made of carbon (C), copper (Cu), or stainless steel, which is stable at a potential lower than the potential at which the reaction of the following formula (3) occurs. It is more preferable to carry functional Pt fine particles.
- the first power supply 51 and the second power supply 52 are DC power supply devices that apply predetermined voltages V1 and V2, respectively, and are connected in series with the first power supply 51 on the positive electrode side.
- the first power source 51 has a positive electrode connected to the first electrode 31 and a negative electrode connected to the second electrode 32 .
- the second power supply 52 has a positive electrode connected to the second electrode 32 and a negative electrode connected to the third electrode 33 .
- the connection node 5n (see FIG. 2) between the first power supply 51 and the second power supply 52 is connected to the second electrode 32.
- the first power supply 51 applies a voltage V1 across the electrolyte membrane 2 to generate a potential gradient for conducting Li + in the electrolyte membrane 2 .
- the second power supply 52 applies a voltage V2 that forms a potential lower than that of the surface of the electrolyte membrane 2 to the aqueous solution AS for recovering Li, so that electrons e ⁇ are transferred from the recovery tank 12 side of the electrolyte membrane 2 to the supply tank 11 side. Suppress conduction.
- the first power supply 51 and the second power supply 52 apply a voltage (V1+V2) between the Li-containing aqueous solution SW and the Li-recovering aqueous solution AS as one power supply.
- the heating device 6 is provided as necessary to bring the electrolyte membrane 2 to a predetermined temperature, and heats the electrolyte membrane 2 via the Li-containing aqueous solution SW or the Li-recovering aqueous solution AS.
- a known heater that heats liquid can be applied to the heating device 6, and preferably has a temperature control function.
- the heating device 6 is of an immersion type (immersion type), and is immersed in the aqueous Li recovery solution AS in the recovery tank 12 . Therefore, the heating portion of the heating device 6 that is immersed in the Li recovering aqueous solution AS is made of a material that does not deteriorate such as corrosion even if it comes into contact with the Li recovering aqueous solution AS, like the treatment tank 1 .
- the heating device 6 only needs to heat the electrolyte membrane 2 to a predetermined temperature, and does not have to keep the Li-containing aqueous solution SW and the Li-recovering aqueous solution AS at a uniform liquid temperature.
- a stirring device may be provided depending on the capacity of the processing tank 1, etc.
- the temperature of the electrolyte membrane 2 may be above the freezing point and below the boiling point of the aqueous solutions SW and AS, and is preferably high as will be described later.
- a circulation device 7 is provided as necessary, and circulates the Li-containing aqueous solution SW between the outside and the supply tank 11 .
- the circulation device 7 includes, for example, a pump and a filter for removing dust and the like.
- the Li-containing aqueous solution SW is seawater, hot spring water, or the like, it is preferable to apply the voltage while circulating the Li-containing aqueous solution SW from these supply sources into the supply tank 11 .
- the Li concentration of the Li - containing aqueous solution SW is kept almost constant even if the recovery of Li + progresses, and the recovery rate of Li is less likely to decrease even with a low-concentration Li aqueous solution. Continuous operation is possible.
- the circulation device 7 may replace the Li-containing aqueous solution SW in the supply tank 11 every time the operation is performed for a certain period of time.
- the lithium recovery apparatus 10 may have a structure in which the supply tank 11 is open to the outside (for example, into the sea) through a filter or the like.
- the Li-containing aqueous solution SW is a Li source and is an aqueous solution containing lithium ions Li + and other metal ions M n + such as Na + and Ca 2+ .
- Examples of such an aqueous solution include an aqueous solution obtained by pulverizing seawater, hot spring water, used lithium ion secondary batteries, etc., dissolving them in acid, and adjusting the pH thereof.
- the Li recovery aqueous solution AS is a solution for containing the lithium ions Li + recovered from the Li-containing aqueous solution SW.
- the Li recovering aqueous solution AS is preferably an aqueous solution containing no metal ions (such as Na + ) other than lithium ions Li + , and may be pure water.
- the aqueous solution AS for recovering Li should be an aqueous solution containing Li + (lithium hydroxide (LiOH) aqueous solution) at the start of recovery (at the start of power application). preferable.
- Lithium recovery method A lithium recovery method according to an embodiment of the present invention will be described with reference to FIGS. 2 and 3.
- FIG. The lithium recovery method according to the present embodiment is performed as follows by using the lithium recovery device 10 according to the embodiment shown in FIG. In addition, in FIG. 2, the heating device 6 and the circulation device 7 are omitted.
- the first power source 51 and the second power source 52 connected in series can be regarded as one power source (referred to as power sources 51-52).
- a positive voltage (V 1 +V 2 ) is applied to the third electrode 33 .
- the following reactions occur in the Li-containing aqueous solution SW in the supply tank 11 .
- the hydroxide ions (OH ⁇ ) in the Li-containing aqueous solution SW undergo the reaction of the following formula (1) to release electrons e ⁇ to produce water (H 2 O) and oxygen (O 2 ) is generated and electrons e ⁇ are emitted to the first electrode 31 .
- the reaction of the following formula ( 1 )' may occur to generate ozone (O3).
- the reaction of the following formula (5) is further caused to release electrons e ⁇ to the first electrode 31 to produce chlorine ( Cl 2 ) is generated according to the type of anions contained in the Li-containing aqueous solution SW.
- Li + in the Li-containing aqueous solution SW moves into the electrolyte membrane 2 in order to maintain the charge balance. occurs near the electrolyte membrane 2 , that is, near the first electrode 31 .
- the following reactions occur in the aqueous Li recovery solution AS in the recovery tank 12 .
- H 2 O in the aqueous solution AS for recovering Li is supplied with electrons e ⁇ to cause the reaction of the following formula (3) to generate hydrogen (H 2 ) and OH ⁇
- the second power supply 52 applies a positive voltage V2 to the second electrode 32 with respect to the third electrode 33 .
- OH - in the aqueous solution AS for recovering Li causes the reaction of the following formula (1) to release electrons e - to the second electrode 32, thereby generating H 2 O and O 2 . generate.
- the electrolyte membrane 2 has a potential gradient in which the potential of the surface on the opposite side (the recovery tank 12 side) is low. It jumps (hops) to a nearby lattice defect site on the deep side of the electrolyte membrane 2 .
- Li + repeatedly moves from the lattice defect site of the electrolyte membrane 2 to the lattice defect site in the vicinity thereof, and finally, as the reaction of the formula (4), the lattice defect site on the surface on the recovery tank 12 side into the aqueous Li recovery solution AS.
- Li + at the lattice defect sites on the surface of the electrolyte membrane 2 on the side of the supply tank 11 moves to the deep part of the electrolyte membrane 2 .
- Li + in the Li - containing aqueous solution SW sinks into the electrolyte membrane 2 and moves in the electrolyte membrane 2 in the same manner.
- the movement of Li + in the electrolyte membrane 2 becomes faster as the potential gradient in the electrolyte membrane 2 increases, that is, as the voltage V1 of the first power supply 51 increases.
- the migration of Li + in the electrolyte membrane 2 is also faster the larger the Li + concentration gradient in the electrolyte membrane 2 is. Therefore, the stronger the electric field between the second electrode 32 and the third electrode 33 in the Li recovery aqueous solution AS, that is, the larger the voltage V2 of the second power supply 52, the easier the reaction of formula (4) becomes, and the electrolyte membrane 2 It is possible to move the Li + in the Li recovering aqueous solution AS at a high speed.
- the reaction of 4) becomes faster, and Li + in the electrolyte membrane 2 can be transferred to the aqueous solution AS for recovering Li.
- the voltage V1 that is, the potential difference between both surfaces of the electrolyte membrane 2 is equal to or higher than the potential at which some of the metal ions constituting the electrolyte membrane 2 are reduced (for example, if the electrolyte membrane 2 is LLTO, Ti 4+ +e ⁇ ⁇ Ti 3+ ). Then, the electrolyte membrane 2 can conduct electrons e ⁇ from the collection tank 12 side to the supply tank 11 side.
- the second power supply 52 connected between the second electrode 32 and the third electrode 33 applies the voltage V2 to the third electrode 33 with the aqueous solution AS for recovering Li. A suitable potential difference is created with electrode 32 being positive.
- the electrons e ⁇ supplied from the third electrode 33 to the Li recovering aqueous solution AS move from the second electrode 32 connected to the surface of the electrolyte membrane 2 to the positive electrode of the second power supply 52 , and the potential of the second electrode 32 increases to That is, the potential of the surface of the electrolyte membrane 2 on the recovery tank 12 side is maintained as high as the O 2 generating potential. Since the O 2 generation potential is higher than the reduction potential of the metal ions composing the electrolyte membrane 2 (in the case of Ti, Ti 4+ +e ⁇ ⁇ Ti 3+ ; ⁇ 0.488 V vs. SHE), the electrolyte membrane 2 does not conduct the electron e ⁇ regardless of the potential difference.
- the voltage V1 can be set to a voltage higher than the applied voltage that causes the electrolyte membrane 2 to reach the reduction potential of at least one metal ion forming the electrolyte membrane 2 .
- the application of the voltage V2 does not allow the electrolyte membrane 2 to reach the reduction potential of the metal ions, and the electrolyte membrane 2 does not transmit electrons e ⁇ .
- the lithium recovery device 10 includes a closed circuit in which a second power source 52, a first power source 51, an electrolyte membrane 2, an aqueous solution AS' for recovering Li, and a second power source 52 are connected in this order in a ring.
- a first power source 51 and a second power source 52 connected in series generate a current I1 counterclockwise as indicated by the arrow with a dot pattern. , I2 flow.
- the current supplied from the first power supply 51 is represented as I1, and the current supplied from the second power supply 52 is represented as I2.
- I1 the current supplied from the first power supply 51
- I2 the current supplied from the second power supply 52
- I1 the current supplied from the second power supply 52
- the electrolyte membrane 2 when electron conductivity is not exhibited, Li + moves in the opposite direction (in the same direction as the current I1) instead of the electron e ⁇ .
- OH ⁇ moves instead of some of the electrons e ⁇ .
- the negative electrode of the first power source 51 and the positive electrode (connection node 5n) of the second power source 52 are connected to the electrolyte membrane 2 and the aqueous solution AS' for recovering Li via the second electrode 32, respectively.
- the lithium recovery device 10 further includes a closed circuit composed of the first power supply 51 and the electrolyte membrane 2, and a closed circuit composed of the second power supply 52 and the Li recovery aqueous solution AS'. A current can flow counterclockwise to one of the .
- the lithium recovery apparatus 10 moves the electrons e ⁇ in the Li recovery aqueous solution AS from the second electrode 32 to the positive electrode of the second power source 52, that is, the second power source 52 and the Li recovery aqueous solution AS′
- Currents I2 and I3 flow as indicated by white arrows in a closed circuit (second circuit) composed of .
- a current branched from the current I2 and supplied to the second electrode 32 (from the connection node 5n) is represented as I3.
- the reaction of formula (3) occurs near the second electrode 32 to generate H 2 and can reach the reduction potential of the metal ion.
- the resistance of the electrolyte membrane 2 (the resistance between the first electrode 31 and the second electrode 32) is expressed as R EL
- the resistance of the Li recovery aqueous solution AS ′ (the resistance between the second electrode 32 and the third electrode 33 ) is expressed as RAS.
- the lithium recovery device 10 further includes a reaction resistance R c1 due to the reaction (O 2 generation) of formula (1) and the reaction (Cl 2 generation) of formula (5) at the first electrode 31, and the reaction resistance R c1 at the second electrode 32 of formula (1) and a reaction resistance R c3 due to the reaction of formula ( 3) (H 2 generation ) at the third electrode 33 .
- the first circuit is expressed by the following equation (6)
- the second circuit is expressed by the following equation (7).
- the resistances of the electrodes 31, 32, 33 and wiring are ignored.
- the following formula (8) is obtained from the formulas (6) and (7).
- the current I1 is represented by the following formula (9) from the following formula (8).
- the current I2 is represented by the following formula (10) from the formula (7).
- the following equation (11) should be established. Solving the equation (11) yields the equation (12). Also, substituting the following formula (9) for I1 in the following formula (10) and solving for I2 yields the following formula (13). Substituting the formula (13) into the formula (12) yields the formula (14).
- the lithium recovery apparatus 10 connects ammeters (not shown) in series to the first power source 51 and the second power source 52, respectively, and applies voltages V1 and V2 while measuring the currents I1 and I2. do it.
- the lower the resistance R AS between the second electrode 32 and the third electrode 33 and the reaction resistance R c3 at the third electrode 33 the smaller the voltage V2 can be set.
- the reaction resistance R c3 decreases as the area of the third electrode 33 immersed in the Li recovering aqueous solution AS increases and as the catalytic activity of the third electrode 33 for the reaction of formula (3) increases.
- the resistance RAS is lower as the area of the second electrode 32 and the third electrode 33 immersed in the aqueous solution AS for Li recovery is larger and the distance between them is shorter. Also, the resistance RAS is lower as the electronic conductivity of the aqueous solution AS for recovering Li is higher.
- the electrolyte membrane 2 does not exhibit electronic conductivity.
- the margin is It is preferable to set the voltage V2 so that I1 ⁇ I2.
- a second power supply 52 connected in series to the negative electrode of the first power supply 51 is provided so that the electrolyte membrane 2 is supplied to the Li recovery aqueous solution AS.
- the third electrode 33 having a potential lower than that of the surface and setting the potential difference, that is, the voltage V2 of the second power supply 52 to correspond to the voltage V1
- the electrolyte membrane 2 has a large potential to reach the reduction potential of the metal ions. Even if a potential difference occurs between the two surfaces, the electron e ⁇ is difficult to conduct.
- the recovery rate of Li + can be increased corresponding to the potential gradient in the electrolyte membrane 2 .
- the first electrode 31 and the second electrode 32 are provided in contact with both surfaces of the electrolyte membrane 2, so that the electrolyte membrane 2 is A potential gradient is efficiently formed at , and the moving speed of Li + in the electrolyte membrane 2 can be increased.
- the voltage V2 of the second power supply 52 is increased in accordance with the increase of the voltage V1 of the first power supply 51, a concentration gradient of Li + is efficiently formed in the electrolyte membrane 2, and the concentration of Li + in the electrolyte membrane 2 is Can speed up movement.
- the movement of Li + in the electrolyte membrane 2 becomes faster as the temperature becomes higher as well as the voltage V1. Therefore, it is preferable that the temperature of the electrolyte membrane 2 is high. Also, the resistances R EL , R SW , and RAS of the electrolyte membrane 2 and the aqueous solutions SW and AS , and the reaction resistances R c1 , R c2 , and R c3 at the electrodes 31, 32, 33 are lower as the temperature is higher.
- the applicable temperature range is from the freezing point to the boiling point of the aqueous solutions SW and AS, preferably 20° C. or higher.
- a lithium recovery apparatus 10A includes a processing tank 1, an electrolyte membrane (lithium ion conductive electrolyte membrane) 2 and an ion exchange membrane 8 that partition the processing tank 1, an electrolyte A first electrode 31 and a second electrode 32 coated on each side of the membrane 2, a third electrode (sub-electrode) 33, an electrode 41, an electrode 42, a first power source 51 and a second power source 52 connected in series, and ion migration.
- a power supply 53 is provided.
- the treatment tank 1 comprises a raw material tank 13 containing a Li-containing aqueous solution SW such as seawater, a supply tank (first tank) 11 containing a Li-containing aqueous solution SW', and an aqueous solution for recovering Li.
- a recovery tank (second tank) 12 for containing AS is partitioned into three in this order.
- the ion exchange membrane 8 partitions the raw material tank 13 and the supply tank 11
- the electrolyte membrane 2 partitions the supply tank 11 and the recovery tank 12 .
- the electrodes 41 and 42 are provided in the raw material tank 13 and the supply tank 11 so as to face the ion exchange membrane 8, respectively.
- the ion transfer power supply 53 is connected between the electrodes 41 and 42 with the electrode 42 provided on the recovery tank 12 side, ie, the supply tank 11 being negative. Therefore, the lithium recovery apparatus 10A according to the present modification differs from the lithium recovery apparatus 10 according to the embodiment shown in FIG. , electrodes 41 and 42 arranged with an ion exchange membrane 8 interposed therebetween, and an ion transfer power supply 53 connected therebetween.
- a Li-containing aqueous solution SW such as seawater is stored in the raw material tank 13 .
- the ion exchange membrane 8 conducts cations containing at least Li + . This prevents the Li-containing aqueous solution SW' in the supply tank 11 from containing anions such as Cl.sup.- .
- the ion exchange membrane 8 is a cation exchange membrane that allows cations to pass through and anions to be blocked, and a monovalent cation selective permeation ion exchange membrane that allows only monovalent cations such as Li + , K + , and Na + to pass through.
- Membranes, bipolar monovalent ion permselective ion exchange membranes that allow monovalent ions to permeate, and the like can be applied.
- Known ion-exchange membranes can be applied.
- NEOSEPTA CSE manufactured by Astom Co., Ltd.
- SELEMION registered trademark
- CSO manufactured by AGC Engineering Co., Ltd.
- CXP-S manufactured by Astom Co., Ltd.
- bipolar NEOSEPTA CIMS manufactured by Astom Co., Ltd.
- the electrodes 41 and 42 are electrodes for applying a voltage between both surfaces of the ion exchange membrane 8 to generate a potential difference that is low on the recovery tank 12 side, ie, high on the raw material tank 13 side.
- the electrodes 41 and 42 can be spaced apart from the ion exchange membrane 8 as shown in FIG. 4 as an example, and the aqueous solutions SW and SW' can contact the entire surface of the ion exchange membrane 8 .
- the electrodes 41 and 42 preferably have a mesh shape or the like through which the aqueous solutions pass so that the aqueous solutions SW and SW' in contact with the surfaces of the ion exchange membranes 8 in the tanks 13 and 11 are continuously exchanged.
- the electrode 42 is spaced apart from the first electrode 31 provided in the same supply tank 11.
- the distance between 8 and electrolyte membrane 2 is designed to be sufficiently long.
- the electrodes 41 and 42 are preferably arranged parallel to each other.
- the electrodes 41 and 42 are formed in the Li-containing aqueous solution SW and the electrode 42 in the Li-containing aqueous solution SW', respectively, and are made of an electrode material that is stable even when a voltage is applied, including after operation of the lithium recovery apparatus 10A (after Li recovery).
- the ion transfer power supply 53 is a DC power supply device, and is connected between the electrodes 41 and 42 so that the recovery tank 12 side is negative.
- the ion transfer power supply 53 applies a voltage V3 to form a potential difference between both surfaces of the ion exchange membrane 8 with a low potential difference on the supply tank 11 side, thereby supplying the metal ions contained in the Li-containing aqueous solution SW in the raw material tank 13. It is moved to the Li-containing aqueous solution SW′ in the bath 11 .
- the Li-containing aqueous solution SW′ accommodates cations including Li + recovered from the Li-containing aqueous solution SW, and also serves as a secondary Li source in the lithium recovery device 10A, such as Cl ⁇ contained in the Li-containing aqueous solution SW. It is a solution for removing anions other than OH - .
- the Li-containing aqueous solution SW′ is preferably an aqueous solution containing no anions other than OH ⁇ , particularly halide ions, and is, for example, pure water at the start of operation of the lithium recovery apparatus 10A.
- the Li-containing aqueous solution SW' has a somewhat high electronic conductivity at the start of operation. It may be an aqueous solution in which Li + or Na + which is an active metal ion is dissolved. That is, the Li-containing aqueous solution SW' is preferably a lithium hydroxide (LiOH) aqueous solution or a sodium hydroxide (NaOH) aqueous solution, preferably a LiOH aqueous solution.
- LiOH lithium hydroxide
- NaOH sodium hydroxide
- the lithium recovery device 10A further includes a heating device 6 and a circulation device (circulation means) 7 as necessary (see FIG. 1).
- the circulation device 7 circulates the Li-containing aqueous solution SW between the outside and the raw material tank 13 .
- the lithium recovery apparatus 10A may have a structure in which the raw material tank 13 is open to the outside (for example, into the sea) through a filter or the like.
- a method of recovering lithium by the lithium recovery device 10A according to this modified example will be described with reference to FIG.
- this modification while moving cations containing Li + from the Li-containing aqueous solution SW in the raw material tank 13 to the Li-containing aqueous solution SW' in the supply tank 11, in parallel, they are recovered from the Li-containing aqueous solution SW'.
- Li + is moved to the aqueous Li recovery solution AS in the tank 12 .
- the ion transfer power source 53 applies a positive voltage V3 (+V3) to the electrode 41 with respect to the electrode 42 . Then, Li + and other metal ions M n + in the Li-containing aqueous solution SW pass through the ion exchange membrane 8 and move to the Li-containing aqueous solution SW'. After a certain amount of Li + has moved to the Li-containing aqueous solution SW', the first power supply 51 and the second power supply 52 start applying the voltages V1 and V2. Then, Li + that has moved to the Li-containing aqueous solution SW′ further moves to the Li recovery aqueous solution AS in the recovery tank 12 .
- the movement of Li + from the Li-containing aqueous solution SW′ in the supply tank 11 to the Li recovery aqueous solution AS in the recovery tank 12 is the same as in the above embodiment (see FIG. 2).
- the Li-containing aqueous solution SW' in contact with the first electrode 31 does not contain Cl.sup.- or the like, so the catalytic activity of the first electrode 31 is not impaired during long-term operation.
- the ion transfer power source 53 is driven to increase the Li + concentration of the Li-containing aqueous solution SW' to some extent, and then the power sources 51 and 52 are started to be driven. is preferable in terms of energy efficiency.
- the moving amount per time to the aqueous solution SW' increases. If the amount of Li + transferred per hour is small, the amount of Li + transferred per hour from the Li-containing aqueous solution SW′ to the Li recovery aqueous solution AS is rate-determined.
- the voltage V3 is greater than a certain value, the reaction of the following formula (1) occurs in the vicinity of the electrode 41 to generate O 2 , and the Li-containing aqueous solution SW contains chloride ions (Cl ⁇ ).
- the reaction of the following formula (5) occurs to generate chlorine (Cl 2 ).
- the reaction of the following formula (3) occurs in the vicinity of the electrode 42 to generate H 2 . Since the energy efficiency decreases as the amount of these reactions increases, it is preferable that the voltage V3 is small within a range in which the amount of Li + transferred from the Li-containing aqueous solution SW′ to the Li-recovering aqueous solution AS does not limit the rate.
- the power supplies 51 and 52 are stopped until a sufficient amount of Li + moves from the Li-containing aqueous solution SW, and the ion transfer Only the power supply 53 may be driven.
- the area of the ion exchange membrane 8 may be made larger than that of the electrolyte membrane 2 .
- the processing tank 1 is supplied so that the cross section perpendicular to the partition direction in the tank is wider at the boundary between the raw material tank 13 and the supply tank 11 than at the boundary between the supply tank 11 and the recovery tank 12. It is possible to form a shape in which the side surfaces (the front and back surfaces in FIG. 4) and the bottom surface of the tank 11 are stepped or inclined.
- the electric field generated by the voltage V3 becomes stronger with respect to the voltage V3 as the distance between the electrodes 41 and 42 and the ion exchange membrane 8 becomes shorter and as the electronic conductivity of the aqueous solutions SW and SW' increases. Therefore, by arranging the electrodes 41 and 42 and setting the Li-containing aqueous solution SW' to be an aqueous solution containing ions at the start of the operation, the movement amount of cations including Li + per time can be increased with respect to the voltage V3. can do.
- the lithium recovery device and the lithium recovery method according to the present invention have been described in terms of the mode for carrying out the present invention. It goes without saying that the present invention is not limited to these examples and the above-described embodiments, and that various modifications and alterations based on these descriptions are also included in the gist of the present invention.
- the amount of lithium transferred by voltage application for a certain period of time was measured.
- the lithium recovery device used a plate-like La 0.57 Li 0.29 TiO 3 (lithium ion conductive ceramics LLTO, manufactured by Toho Titanium Co., Ltd.) of 50 mm ⁇ 50 mm and 0.5 mm thickness as an electrolyte membrane. 19.5 mm grid-shaped electrodes with a thickness of 10 ⁇ m, a width of 0.5 mm, and an interval of 0.5 mm are provided as the first electrode and the second electrode (electrodes with a porous structure) at the respective central portions of both surfaces of the electrolyte membrane. It was formed to have a size of ⁇ 20.5 mm, and a lead wire for connection to a power source was formed to be connected to this electrode.
- La 0.57 Li 0.29 TiO 3 lithium ion conductive ceramics LLTO, manufactured by Toho Titanium Co., Ltd.
- the first electrode, the second electrode, and the lead wire were formed by screen-printing a Pt paste on the surface of the electrolyte membrane and baking it at 900° C. for 1 hour in the atmosphere.
- a 20 mm ⁇ 20 mm Ni mesh electrode was used as the third electrode (sub-electrode).
- An electrolyte membrane with electrodes formed thereon is mounted in a treatment tank made of an acrylic plate, which is divided into a supply tank and a recovery tank, and a third electrode is placed in the recovery tank so as to face the second electrode on the surface of the electrolyte membrane. (distance between the third electrode and the electrolyte membrane: 50 mm).
- the processing bath was housed in a constant temperature bath having a temperature control function.
- a first power source is connected between the first electrode and the second electrode with the first electrode as a positive electrode
- a second power source is connected in series to the negative electrode of the first power source
- the negative electrode is connected to the second electrode.
- a lithium recovery device Ammeters were inserted between the first power supply and the first electrode, and between the second power supply and the first power supply and the third electrode (between the second power supply 52 and the connection node 5n in FIG. 2).
- a 1 mol/l lithium hydroxide aqueous solution is prepared as the Li-containing aqueous solution and the Li recovery aqueous solution, and the first electrode, the second electrode, and the third electrode are completely immersed in 150 ml each of the supply tank and the recovery tank of the lithium recovery device. I put it in like In addition, the same lithium hydroxide aqueous solution as a replacement is stored in a replenishment tank installed outside the treatment tank of the lithium recovery device in the constant temperature tank, and adjusted to the same liquid temperature as the lithium hydroxide aqueous solution in the supply tank and recovery tank. did.
- Lithium recovery experiment A DC voltage was applied for 1 h by the first power supply and the second power supply.
- the lithium hydroxide aqueous solution is pumped from the replenishing tank to the supply tank and the collection tank at a constant speed by a liquid feed pump.
- the aqueous solution was pumped at the same rate as each tank was refilled.
- the concentration of Li in the aqueous solution in the recovery tank and the aqueous solution pumped out from the recovery tank was measured with an inductively coupled plasma optical emission spectrometer (ICP-OES) (Optima 7000DV, manufactured by PerkinElmer Co., Ltd.) for 1 h.
- ICP-OES inductively coupled plasma optical emission spectrometer
- the amount of movement of Li due to voltage application was calculated.
- FIG. 5 Graphs of the amount of movement of Li per time are shown in FIG. 5 (voltage V1 dependence), FIG. 6 (voltage V2 dependence), and FIG. 7 (input power (power supply output) dependence).
- the Li transfer amount per 1 J ((Li transfer amount per 1 h / 3600) / power supply output) is calculated, and the total voltage (V1 + V2) dependence of the first power supply and the second power supply
- FIG. 8A shows a graph of input power dependence of the first power supply and the second power supply
- FIG. 8A shows a graph of input power dependence of the first power supply and the second power supply
- FIG. 8A shows a graph of input power dependence of the first power supply and the second power supply
- FIG. 8A shows a graph of input power dependence of the first power supply and the second power supply
- FIG. 8A shows a graph of input power dependence of the amount of movement of Li
- the first power supply can apply a large voltage V1 between both surfaces of the electrolyte membrane, thereby increasing the recovery rate of Li. was made.
- the voltage V2 As shown in FIG. 6, as the voltage V2 increases in the range where I1 ⁇ I2, the current I2 sharply increases, so the power output increases. Therefore, as shown in FIG. 7, it was possible to efficiently increase the amount of movement of Li + per time by increasing the voltage V1 rather than the voltage V2. Furthermore, as shown in FIGS. 8A and 8B, the energy efficiency of Li + transfer improved as the voltage V1 increased, but decreased as the voltage V2 increased. Therefore, it can be said that the voltage V2 is preferably smaller within the range of I1 ⁇ I2.
- the lithium recovery device and the lithium recovery method according to the embodiment of the present invention realize high-speed recovery of Li.
Abstract
Description
図1に示すように、本発明の実施形態に係るリチウム回収装置10は、処理槽1、処理槽1を仕切る電解質膜(リチウムイオン伝導性電解質膜)2、電解質膜2の各面に被覆した第1電極31と第2電極32、第3電極(副電極)33、直列に接続した第1電源51および第2電源52、加熱装置6、ならびに循環装置(循環手段)7を備える。処理槽1は、電解質膜2によって、海水等のLi含有水溶液SWを収容する供給槽(第1槽)11と、Li回収用水溶液ASを収容する回収槽(第2槽)12と、の2つに仕切られている。第3電極33は、回収槽12内に電解質膜2から離間して設けられる。第1電源51は、正(+)極が第1電極31に接続され、負(-)極が第2電極32に接続される。第2電源52は、第1電源51の負極に直列に接続する、すなわち正極が第2電極32に接続されると共に、負極が第3電極33に接続される。したがって、本実施形態に係るリチウム回収装置10は、電気透析法による従来のリチウム回収装置(例えば、図10に示すリチウム回収装置100)に対して、第1電源51(図10の電源151)の負極に直列に接続した第2電源52、およびその負極に接続する第3電極33を追加した構成である。以下、本発明の実施形態に係るリチウム回収装置を構成する各要素について説明する。
本発明の実施形態に係るリチウム回収方法について、図2および図3を参照して説明する。本実施形態に係るリチウム回収方法は、図1に示す実施形態に係るリチウム回収装置10により、以下のように行う。なお、図2において、加熱装置6および循環装置7は省略する。
Li含有水溶液SWが海水である等、Cl-を含有する場合、Ptで形成された第1電極31の表面に塩化白金(PtCl2)が形成されてPtの高い触媒活性が損なわれ、電極反応過電圧が増大して式(1)の反応速度が低下する。そこで、海水等をLi源とする場合には、第1電極31にCl-が接触しないように、以下の構成とした。以下、本発明の実施形態の変形例に係るリチウム回収装置およびリチウム回収方法について、図4を参照して説明する。前記実施形態(図1~図3参照)と同一の要素については同じ符号を付し、説明を適宜省略する。
リチウム回収装置は、電解質膜として、50mm×50mm、厚さ0.5mmの板状のLa0.57Li0.29TiO3(リチウムイオン伝導性セラミックスLLTO、東邦チタニウム(株)製)を使用した。この電解質膜の両面のそれぞれの中央部に、第1電極および第2電極(多孔質構造の電極)として、厚さ10μm、幅0.5mm、間隔0.5mmの格子状の電極を19.5mm×20.5mmの大きさに形成し、さらにこの電極に接続する、電源に接続するためのリード線を形成した。第1電極、第2電極、およびリード線は、Ptペーストを電解質膜の表面にスクリーン印刷し、大気中において900℃で1h焼成して形成した。また、第3電極(副電極)として、20mm×20mmのNiメッシュ電極を使用した。電極等を形成した電解質膜を、アクリル板製の処理槽内に装着して供給槽と回収槽に仕切り、回収槽内に、第3電極を電解質膜表面の第2電極に正対するように配置した(第3電極-電解質膜間距離:50mm)。さらに処理槽を、温度調整機能を有する恒温槽に収容した。そして、第1電極と第2電極の間に、第1電極を正極として第1電源を接続し、第1電源の負極に第2電源を直列に接続すると共にその負極を第2電極に接続し、リチウム回収装置とした。また、第1電源と第1電極の間、第2電源と第1電源および第3電極との間(図2の第2電源52と接続ノード5nの間)に、それぞれ電流計を挿入した。
第1電源と第2電源で直流電圧を1h印加した。電気透析に伴う供給槽内、回収槽内の水酸化リチウム水溶液濃度の変化を抑制するために、電圧を印加しながら、補充槽から水酸化リチウム水溶液を液送ポンプにより一定速度で供給槽および回収槽のそれぞれに補充すると共に、同じ速度で水溶液を汲み出した。そして、電圧印加後に、回収槽内の水溶液および回収槽から汲み出した水溶液のLi濃度を、誘導結合プラズマ発光分析(ICP-OES)装置(Optima7000DV、(株)パーキンエルマー製)で測定し、1hの電圧印加によるLiの移動量を算出した。また、電圧印加時に電流計で計測した電流(1hにおける平均値)I1,I2に基づき、電源出力P(=V1・I1+V2・I2)を算出した。
本実施例に係るリチウム回収装置の電解質膜の、電子伝導性を発現する印加電圧を確認した。リチウム回収装置から第2電源および第3電極を取り外した図10に示す構成として、前記実験と同様に供給槽内、回収槽内の水酸化リチウム水溶液を交換しながら、第1電源で電圧V1を1h印加した。液温は40℃とし、電圧V1を0.5Vから0.5V刻みで増加させ、電流I1が急増した2.5Vまで実験を行った。測定したLiの移動量は、計測した電流I1に基づくLi移動量に対し、電圧V1が2.0V以下ではほぼ100%であったが、電圧V1が2.5Vでは約30%に低下した。したがって、本実施例において、電解質膜は、両面間の印加電圧が2.0V超2.5V以下で電子伝導性を発現するといえる。
図5に示すように、第2電源により電圧V2を印加することにより、電解質膜の両面間への印加電圧V1を大きくするにしたがい、電解質膜の電子伝導性を発現させる電位差以上に大きくしても、Li+の時間あたりの移動量が増加した。また、図6に示すように、電圧V2を大きくしても、Li+の時間あたりの移動量が増加した。ただし、V1=2VにおいてはV1=5Vと比較して著しく少なかった。なお、図6に示すように、V1=5Vにおいて、電圧V2が5V以上ではI1<I2であったが、電流I1,I2を破線で示すように線形近似すると、電圧V2が4.4V近傍以下でI1>I2に逆転することになる。電圧V2をさらに小さくすると、電解質膜の電子伝導性が発現してLi+の移動量がV1=2Vと同程度に激減すると推測される。このように、第2電源を設けて十分な大きさの電圧V2を印加することにより、第1電源で電解質膜の両面間に大きな電圧V1を印加して、Liの回収速度を高速化することができた。
図9に示すように、温度が高いほどLi+の時間あたりの移動量が増加した。これは、電解質膜の温度を高くすることにより、電解質膜中でのLi+の移動速度が高速になり、Liの回収速度を高速化することができるといえる。
1 処理槽
11 供給槽(第1槽)
12 回収槽(第2槽)
2 電解質膜(リチウムイオン伝導性電解質膜)
31 第1電極(多孔質構造の電極)
32 第2電極(多孔質構造の電極)
33 第3電極(副電極)
51 第1電源
52 第2電源
6 加熱装置
7 循環装置(循環手段)
AS Li回収用水溶液
SW,SW´ Li含有水溶液
Claims (6)
- 第1槽と第2槽とに仕切られた処理槽を備え、前記第2槽に収容した水または水溶液へ、前記第1槽に収容したリチウムイオンを含有する水溶液からリチウムイオンを移動させるリチウム回収装置であって、
前記処理槽を仕切るリチウムイオン伝導性電解質膜と、
前記リチウムイオン伝導性電解質膜の両面にそれぞれ接触させて設けられた多孔質構造の電極と、
前記第2槽内に、前記多孔質構造の電極および前記リチウムイオン伝導性電解質膜から離間して設けられた副電極と、
前記多孔質構造の電極同士の間に、前記第1槽の側を正極として接続する第1電源と、
前記第1電源の負極に直列に接続すると共に、前記副電極に負極を接続する第2電源と、を備え、
前記第1電源および前記第2電源が電圧を印加している時に、前記第2槽側の前記多孔質構造の電極に電流が、流れないまたは前記第2電源の正極から流れることを特徴とするリチウム回収装置。 - 前記第1電源の電圧は、前記リチウムイオン伝導性電解質膜に含まれる少なくとも1種の金属元素の還元電位に到達させる前記リチウムイオン伝導性電解質膜への印加電圧以上であることを特徴とする請求項1に記載のリチウム回収装置。
- 前記リチウムイオン伝導性電解質膜を加熱する加熱装置を備えることを特徴とする請求項1または請求項2に記載のリチウム回収装置。
- リチウムイオンを含有する水溶液を、外部と前記第1槽内との間で循環させる循環手段を備えることを特徴とする請求項1乃至請求項3のいずれか一項に記載のリチウム回収装置。
- リチウムイオン伝導性電解質膜で第1槽と第2槽とに仕切られた処理槽において、前記第2槽に収容した水または水溶液へ、前記第1槽に収容したリチウムイオンを含有する水溶液からリチウムイオンを移動させるリチウム回収方法であって、
前記リチウムイオン伝導性電解質膜の両面にそれぞれ接触させて設けられた多孔質構造の電極同士の間に、前記第1槽の側を正極として接続した第1電源と、
前記第1電源の負極に直列に接続すると共に、負極を前記リチウムイオン伝導性電解質膜から離間して前記第2槽内に設けられた副電極に接続した第2電源と、が、
前記第2槽の側に設けられた前記多孔質構造の電極に電流が、流れないまたは前記第2電源の正極から流れるように、電圧を印加することを特徴とすることを特徴とするリチウム回収方法。 - 前記第1電源が、前記リチウムイオン伝導性電解質膜に含まれる少なくとも1種の金属元素の還元電位に到達させる前記リチウムイオン伝導性電解質膜への印加電圧以上の電圧を印加することを特徴とすることを特徴とする請求項5に記載のリチウム回収方法。
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