Patent ID: 11905180
Assignee: TORAY INDUSTRIES, INC.
Field: Chemical engineering (Chemistry)
Classification: CPC B  C  H  Y | IPC B  C

Claim 0:
1. A method for recovering a rare metal salt, the method comprising:
an acid treatment step of obtaining a rare metal-containing acidic aqueous solution by bringing a material comprising a monovalent rare metal and a polyvalent rare metal into contact with an acidic aqueous solution;
a separation step of obtaining permeated water comprising the monovalent rare metal and non-permeated water comprising the polyvalent rare metal from the rare metal-containing acidic aqueous solution by using a nanofiltration membrane satisfying the condition (1) below; and
a concentration step of obtaining non-permeated water having a higher concentration of the monovalent rare metal and permeated water having a lower concentration of the monovalent rare metal than that of the permeated water in the separation step, by using a reverse osmosis membrane,
condition (1):
a difference between a removal ratio of magnesium sulfate and a removal ratio of magnesium chloride is 20% or less when a 2000 mg/L magnesium sulfate aqueous solution and a 2000 mg/L magnesium chloride aqueous solution, each having a pH of 6.5 and a temperature of 25° C., are respectively allowed to pass through the nanofiltration membrane under an operating pressure of 0.5 MPa; and
a difference between a removal ratio of glucose and a removal ratio of isopropyl alcohol is 40% or more and the removal ratio of glucose is 70% or more when a 1000 mg/L glucose aqueous solution and a 1000 mg/L isopropyl alcohol aqueous solution, each having a pH of 6.5 and a temperature of 25° C. are respectively allowed to pass through the nanofiltration membrane under an operating pressure of 0.5 MPa.