Enhanced water permeance and EDCs rejection using a UiO-66-NH2-predeposited polyamide membrane

Abstract

Endocrine disrupting compounds (EDCs) have been increasingly detected in drinking water sources, and pose severe threat to human health. Polyamide (PA) based nanofiltration (NF) membrane has great potential for EDCs removal from water, but the removal of hydrophobic EDCs is not satisfying due to strong hydrophobic affinity. In this study, UiO-66-NH2/PA membranes were prepared by predepositing hydrophilic UiO-66-NH2 onto the substrate prior to interfacial polymerization. The UiO-66-NH2 aggregates increased the permeable area and strengthened the “gutter effect”. Therefore, the pure water flux of UiO-66-NH2/PA increased by 115% compared with that of the thin-film composite (TFC) membrane, and its rejection of Na2SO4 was 96%. The hydrophilicity-enhanced PA film reduced its adsorption of EDCs and decreased the driving force for EDCs diffusion. Moreover, the UiO-66-NH2-induced hydrophilic nanochannels, including the interfacial gaps between PA film and UiO-66-NH2 aggregates, the gaps in UiO-66-NH2 aggregates, and the inherent pores in UiO-66-NH2 crystals, alleviated the hydrophobic affinity and effectively restricted EDCs diffusion. The rejection rates of methylparaben, propylparaben, bisphenol A, and benzylparaben by the optimal UiO-66-NH2/PA were 50%, 67%, 75%, and 85%, respectively, and the water/benzylparaben selectivity was 4.4 times as high as that of TFC. The results demonstrate that incorporating hydrophilic metal-organic frameworks (MOFs) can improve the membrane hydrophilicity and create hydrophilic nanochannels, and is an effective strategy to enhance EDCs removal by nanofiltration.