Method of separating and recovering cobalt salt and nickel salt
A method of separating and recovering a cobalt salt and a nickel salt includes a separation step of separating, by using a nanofiltration membrane, a cobalt salt and a nickel salt from a rare metal-containing aqueous solution containing at least both the cobalt salt and the nickel salt as rare metals, in which the nanofiltration membrane has a glucose permeability of 3 times or more a sucrose permeability, the sucrose permeability of 10% or less, and an isopropyl alcohol permeability of 50% or more when a 1,000 mg/L glucose aqueous solution, a 1,000 mg/L sucrose aqueous solution, and a 1,000 mg/L isopropyl alcohol aqueous solution, each having a pH of 6.5 and a temperature of 25° C., individually permeate through the nanofiltration membrane at an operating pressure of 0.5 MPa.
1. A method of separating and recovering a cobalt salt and a nickel salt, the method comprising a separation step of separating, by using a nanofiltration membrane, a cobalt salt and a nickel salt from a rare metal-containing aqueous solution containing at least both the cobalt salt and the nickel salt as rare metals,
wherein the nanofiltration membrane has a glucose permeability of 3 times or more a sucrose permeability, the sucrose permeability of 10% or less, and an isopropyl alcohol permeability of 50% or more when a 1,000 mg/L glucose aqueous solution, a 1,000 mg/L sucrose aqueous solution, and a 1,000 mg/L isopropyl alcohol aqueous solution, each having a pH of 6.5 and a temperature of 25° C., individually permeate through the nanofiltration membrane at an operating pressure of 0.5 MPa.
2. The method according to claim 1 , wherein the nanofiltration membrane comprises a base material, a support membrane on the base material, and a separation function layer on the support membrane, and
the separation function layer comprises a polyamide having a structure derived from a polyfunctional aliphatic amine and a structure derived from a polyfunctional acid halide.
3. The method according to claim 2 , wherein the polyfunctional aliphatic amine is a compound represented by formula (1),
provided that R 1 and R 2 each independently represent an alkyl group having 1 to 6 carbon atoms, a phenyl group, a benzyl group, COOR 5 , CONHR 5 , CON(R 5 ) 2 , or OR 5 , and R 5 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group; and R 3 and R 4 each independently represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a benzyl group, COOR 6 , CONHR 6 , CON(R 6 ) 2 , or OR 6 , and R 6 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group.
4. The method according to claim 2 , wherein the polyamide is a crosslinked aromatic polyamide having a structure represented by formula (2),
provided that R 1 and R 2 each independently represent an alkyl group having 1 to 6 carbon atoms, a phenyl group, a benzyl group, COOR 5 , CONHR 5 , CON(R 5 ) 2 , or OR 5 , and R 5 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group; R 3 and R 4 each independently represent hydrogen, an alkyl group having 1 to 6 carbon atoms, a phenyl group, a benzyl group, COOR 6 , CONHR 6 , CON(R 6 ) 2 , or OR 6 , and R 6 represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a phenyl group, or a benzyl group; R 7 is an aliphatic chain or an aliphatic ring comprising only a carbon atom and a hydrogen atom as a constituent element; and Ar 8 is an aromatic ring having 6 to 14 carbon atoms which may have a substituent.
5. The method according to claim 1 , further comprising a complex forming step of adding a complex forming agent to the rare metal-containing aqueous solution before the separation step,
wherein the complex forming agent has a solubility in water of 100 mg/L or more.
6. The method according to claim 5 , wherein the complex forming step comprises a step of adjusting a pH of the rare metal-containing aqueous solution to 1 or more and 9 or less.
7. The method according to claim 5 , wherein the complex forming step comprises a step of adding an amine-based ligand as the complex forming agent.
8. The method according to claim 1 , further comprising, before the separation step, an acid treatment step of bringing a material containing at least both cobalt and nickel as rare metals into contact with an acid aqueous solution to obtain the rare metal-containing aqueous solution.
9. The method according to claim 8 , further comprising a mixing step of mixing a permeated water generated in a concentration step with the rare metal-containing aqueous solution obtained in the acid treatment step,
wherein, in the separation step, the permeated water and a concentrated water are obtained from a mixed water obtained in the mixing step.
10. The method according to claim 1 , wherein the separation step comprises at least a first separation step and a 2a-th separation step which use the nanofiltration membrane, and
a permeated water obtained in the first separation step is treated in the 2a-th separation step.
11. The method according to claim 10 , wherein the permeated water obtained in the first separation step is diluted to be treated in the 2a-th separation step.
12. The method according to claim 1 , wherein the separation step comprises at least a first separation step and a 2b-th separation step which use the nanofiltration membrane, and
a non-permeated water obtained in the first separation step is treated in the 2b-th separation step.
13. The method according to claim 12 , wherein the non-permeated water obtained in the first separation step is diluted to be treated in the 2b-th separation step.
14. The method according to claim 1 , further comprising, before the separation step, a pre-separation step of separating an alkali metal salt and a polyvalent rare metal salt by using the nanofiltration membrane, to obtain a permeated water in which an alkali metal ion concentration (mg/L) is 100 times or more a polyvalent rare metal ion concentration (mg/L).
15. The method according to claim 1 , further comprising a concentration step of concentrating an aqueous solution obtained in the separation step with a reverse osmosis membrane.