Precise ions sieving in polyamide nanofiltration membranes via sustained diffusion release

It is a great challenge to achieve precise ion sieving by polyamide nanofiltration membrane separation. The key for solving this problem is the fine control of polyamide nanofiltration membrane pore structure. In this study, we propose a PIP pre-diffusion and TMC control release method to fabricate polyamide nanofiltration membrane. The PIP pre-diffusion and TMC control release offered a uniform PIP distribution and adjustable monomer ratio, therefore relatively narrowing pore size distribution. M-60s membrane has 91.5 % of pores smaller than the diameter of hydrated magnesium ions (0.86 nm) and 83.6 % smaller than that of sulfate ions (0.76 nm). In comparison, only 62.7 % and 45.3 % of the pores in the CIP membrane are smaller than these hydrated diameters. Therefore, the membrane exhibited high ions selectivity including Li + /Mg 2+ and Cl − /SO 4 2− of 44.6 and 256.4 respectively. The strategy proposed in the current study might offer a new approach for fabricating nanofiltration membrane with high ions selectivity.