Amino-phosphorylated nanofiber membranes for highly selective and efficient separation of In(III)

The separation and recovery of indium from smelting wastes is of great importance. The development of an adsorbent material with high selectivity and easy handling and recovery for the selective adsorption of In(III) remains a challenge. Polyacrylonitrile modified nanofiber membranes (P-PAN) enriched with amine and phosphonic acid groups were prepared for highly selective adsorptive separation of In(III). The adsorption capacity of the resulting membranes for In(III) in solution was 55.05 mg·g −1 , and the adsorption regeneration rate of the membranes was more than 90 % after seven cycles. The separation factors of the P-PAN nanofiber membranes for β In/Fe , β In/Cu , β In/Zn and β In/Pb in a five-member mixed solution were 209.6, 397, 462.6, and 259.6, respectively. Experimental and theoretical calculations show that the joint action of P OH and P O in the P-PAN nanofiber membranes to form an electron-rich region makes the electrostatic potential energy in this region reach the maximum negative value (−52.02 kcal/mol), which is strongly attracted to In(III). In addition, the adsorption energy of P-PAN nanofiber membranes for In(III) was −494.56 kcal/mol, which was much higher than that of competing ions such as Fe(II), Cu(II), Zn(II), and Pb(II). The findings support the feasibility of regulating the binding capacity of adsorption sites to target metal ions via the protonation of –NH, thereby enhancing selectivity towards these ions.