Method for recovering rare metal salt

Patent metadata

Field	Value
Publication number	US-11905180-B2
Application number	US-202117920148-A
Country	US
Kind code	B2
Filing date	Apr 21, 2021
Priority date	Apr 21, 2020
Publication date	Feb 20, 2024
Grant date	Feb 20, 2024

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

The invention claimed is:

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 the rare metal-containing acidic aqueous solution in the separation step comprises lithium as the monovalent rare metal, and a lithium ion concentration in the rare metal-containing acidic aqueous solution 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 rare metal-containing acidic aqueous solution 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 rare metal-containing acidic aqueous solution 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 rare metal-containing acidic aqueous solution 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

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

• C01D15/04 Primary

  Halides · CPC title

• B01D61/025

  Reverse osmosis; Hyperfiltration · CPC title

• B01D61/027

  Nanofiltration · CPC title