Graphene Oxide/Polyamide-Based Nanofiltration Membranes for Water Purification

A novel electric field-assisted strategy to fabricate graphene oxide (GO)-functionalized nanofiltration (NF) membranes was reported. The resulting polyamide (PA) NF membranes were formed by interfacial polymerization (IP) of trimesoyl chloride (TMC) in an organic phase and piperazine as well as GO with a concentration between 0.1 and 0.5 in the water phase under an electric field using a polysulfone (PSF) ultrafiltration membrane as a substrate. Due to the electric field-induced repulsion in GO during polymerization, the resulting GO/PA nanofiltration membranes showed a Turing-like structure in the composite functional layer as well as higher hydrophilicity. As a result, a substantially improved water flux was observed, and TFC-G0.3-DC even showed a water permeability of 28.5 L·m–2·h–1·bar–1, which is ∼30% higher than that of its analogue TFC-G0.3 without an electric field. Additionally, the TFC-G0.3-DC NF membrane also demonstrated high rejection rates for Na2SO4 (97.6%) and MgSO4 (97.3%) at 4 bar but relatively low NaCl rejection (25.1%), which suggests that it has the potential to separate divalent and monovalent ions. More importantly, GO-PA composite nanofiltration membranes also exhibited excellent antifouling properties with HA and BSA flux recovery rates reaching more than 95%. The simultaneously enhanced water flux, high divalent/monovalent ion selectivity, and improved antifouling property by the electric field are promising advances that may impact applications of NF membranes in water purification.