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

Claim 16:
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 (IA/I1242) 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 and 1.0 or less as compared with a peak intensity ratio (IA/I1242) measured before the immersion,
provided that IA and I1242 are the following absorption peak values, respectively,
IA: absorption peak value corresponding to the separation function layer present in the range of 1600 cm−1 to 1700 cm−1 
I1242: absorption peak value corresponding to the porous support layer at 1242 cm−1.