Asymmetric porous monovalent cation perm-selective membranes with an ultrathin polyamide selective layer for cations separation

Asymmetric porous monovalent cation perm-selective membranes were fabricated by decorating an ultrathin polyamide selective layer on negatively charged porous substrate via interfacial polymerization. The compact and low charge density surface greatly restrained the transport of large-sized Mg2+ while negligible effect was observed for smaller-sized Na+, which resulted in a significant boost in perm-selectivity. When ethylenediamine served as the amine monomer, the corresponding membrane exhibited the excellent perm-selectivity of 3.3 with the ion flux of 4.27 × 10−8 mol cm−2 s−1 at a current density of 14 mA cm−2.353