Method for recovering rare metal salt

Patent metadata

Field	Value
Publication number	US-2023202854-A1
Application number	US-202117920148-A
Country	US
Kind code	A1
Filing date	Apr 21, 2021
Priority date	Apr 21, 2020
Publication date	Jun 29, 2023
Grant date	—

Abstract

The present invention relates to a method for recovering a rare metal salt, the method including: an acid treatment step of obtaining a rare metal-containing acidic aqueous solution by bringing a material including a monovalent rare metal and a polyvalent rare metal into contact with an acidic aqueous solution; a separation step of obtaining permeated water including the monovalent rare metal and non-permeated water including the polyvalent rare metal from the rare metal-containing acidic aqueous solution by using a nanofiltration membrane satisfying the condition (1); 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.

First claim

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.

2 . The method for recovering a rare metal salt according to claim 1 , wherein raw water in the separation step comprises lithium as the monovalent rare metal, and a lithium ion concentration in the raw water is in a range of 0.5 mg/L or more and 50000 mg/L or less.

3 . The method for recovering a rare metal salt according to claim 1 , wherein a total ion concentration of the polyvalent rare metal in the raw water in the separation step is in a range of 0.5 mg/L or more and 100000 mg/L or less.

4 . The method for recovering a rare metal salt according to claim 1 , wherein the raw water in the separation step comprises at least one metal of cobalt, nickel, and manganese as the polyvalent rare metal.

5 . The method for recovering a rare metal salt according to claim 1 , wherein the separation step comprises at least a first separation step of obtaining permeated water and non-permeated water by a nanofiltration membrane and a 2a-th separation step of obtaining permeated water and non-permeated water by further treating the permeated water obtained in the first separation step by a nanofiltration membrane.

6 . The method for recovering a rare metal salt according to claim 1 , wherein the separation step comprises at least the first separation step of obtaining permeated water and non-permeated water by a nanofiltration membrane and a 2b-th separation step of obtaining permeated water and non-permeated water by further treating the non-permeated water obtained in the first separation step by a nanofiltration membrane .

7 . The method for recovering a rare metal salt according to claim 1 , wherein permeated water having a lithium ion concentration (mg/L) of 1000 times or more as high as a polyvalent metal ion concentration (mg/L) is obtained in the separation step.

8 . The method for recovering a rare metal salt according to claim 1 , wherein an operating pressure in the separation step is equal to or lower than an osmotic pressure of the raw water supplied to the nanofiltration membrane.

9 . The method for recovering a rare metal salt according to claim 1 , further comprising, between the acid treatment step and the separation step, a pretreatment step of treating the rare metal-containing acidic aqueous solution with a microfiltration membrane having an average surface pore diameter of 0.05 µm to 10 µm.

10 . The method for recovering a rare metal salt according to claim 1 , further comprising, between the acid treatment step and the separation step, a pretreatment step of treating the rare metal-containing acidic aqueous solution with an ultrafiltration membrane having an average surface pore diameter of 3 nm to 16 nm.

11 . The method for recovering a rare metal salt according to claim 9 , wherein in the pretreatment step, a temperature of the rare metal-containing acidic aqueous solution to be treated is 0° C. to 100° C.

12 . The method for recovering a rare metal salt according to claim 1 , wherein
the concentration step comprises a concentration step of obtaining non-permeated water having a higher concentration of the monovalent rare metal than that of the permeated water in the separation step 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 satisfying the following condition (2), condition (2): a removal ratio of isopropyl alcohol is 95% or more and a removal ratio of boron ions is 75% or more when the reverse osmosis membrane is immersed in a sulfuric acid aqueous solution having a pH of 1 and a temperature of 25° C. for 24 hours, and then an aqueous solution having a pH of 6.5 and a temperature of 25° C. and comprising 30 mg/L boric acid, 100 mg/L isopropyl alcohol, and 30000 mg/L lithium chloride is allowed to pass through the reverse osmosis membrane under an operating pressure of 5.5 MPa.

13 . The method for recovering a rare metal salt according to claim 1 , wherein the concentration step comprises at least first and second concentration steps which use the reverse osmosis membrane, and non-permeated water obtained in the first concentration step is treated in the second concentration step.

14 . The method for recovering a rare metal salt according to claim 1 , further comprising a mixing step of mixing the permeated water produced in the concentration step with the rare metal-containing acidic aqueous solution obtained in the acid treatment step,
wherein, in the separation step, the permeated water and the non-permeated water are obtained from a mixed water obtained in the mixing step.

15 . The method for recovering a rare metal salt according to claim 1 , wherein a nanofiltration membrane having a positive value of surface zeta potential at pH 3 is used as the nanofiltration membrane.

16 . The method for recovering a rare metal salt according to claim 1 , wherein
the nanofiltration membrane comprises a base material, a porous support layer on the base material, and a separation function layer on the porous support layer, the separation function layer comprises a crosslinked polyamide, and a total proportion of halogen in elements measured in X-ray photoelectron spectroscopy measurement of a surface on a separation function layer side is less than 0.1%.

17 . The method for recovering a rare metal salt according to claim 1 , wherein
the nanofiltration membrane comprises a base material, a porous support layer on the base material, and a separation function layer on the porous support layer, and there is only one peak having a maximum in a range of 1600 cm -1 to 1700 cm -1 when a surface on the separation function layer side is measured by a total reflection infrared absorption spectrum method, and when the peak is defined as a peak A, a peak intensity ratio (I A /I 1242 ) measured after immersing the nanofiltration membrane in a 1 M sulfuric acid aqueous solution at 40° C. for 21 days is 0.40 or more

Assignees

• Toray Industries

Inventors

• Yoshizaki Tomoya
• Soya Takanori
• Koiwa Masakazu
• Hanada Shigehisa

Classifications

• B01D69/1071

  Woven, non-woven or net mesh · CPC title

• B01D69/12

  Composite membranes; Ultra-thin membranes · CPC title

• B01D2325/02832

  1-10 nm · CPC title

• B01D2325/02834

  more than 0.1 and up to 1 µm · CPC title

• B01D61/027

  Nanofiltration · CPC title