Investigation on the rejection of mixed salt solution by g-C3N4 functionalized nanofiltration membrane

The use of nanofiltration membrane technologies for seawater desalination is one of the effective ways to solve the shortage of water resources . However, traditional commercial membrane cannot maintain the excellent rejection for a variety of salt ions in mixed salt solutions , while ensuring the excellent permeance flux. In this study, g-C 3 N 4 functionalized nanofiltration membranes of special charge distribution on the surface were prepared by interfacial polymerization to investigate the rejection performance of mixed salt solution (Na 2 SO 4 /NaCl, CaCl 2 /NaCl). Compared with the traditional commercial nanofiltration membrane , the polyamide nanofiltration membrane intercalated with g-C 3 N 4 has excellent rejection performance of a permeance flux of 50.76 L ∙ m −2 h −1 and 50% retention improvement for both monovalent and divalent ions . In addition, the composite membrane has a good anti-fouling performance in both bovine serum albumin and humic acid solutions. • The rejection of both monovalent and divalent ions in the mixed salt solution increases by 50%∼100% with the commercial membranes. • Carbon nitride improves the hydrophilicity significantly; the permeance flux increases from 15.46 L ∙ m −2 h −1 to 50.76 L ∙ m −2 h −1 . • Nanomaterial improves the anti-fouling performance of composite membranes significantly. • The exclusion mechanism in single/mixed salt solution is analyzed by SEDE model.