Construction of facilitated mass transfer composite membranes with triple-layer water nanochannel architecture for forward osmosis process using cGO-coated polysulfone separation membrane as the substrate

Abstract

Forward osmosis (FO) composite membrane with triple-layer water nanochannel architecture was constructed to improve membrane permeability. A hydrophilic carboxylated graphene oxide (cGO)–polyamide (PA) composite was prepared through interfacial polymerization (IP) of m-phenylenediamine (MPD) and trimesoyl chloride (TMC). The cGO nanosheet-coated polysulfone (PSF) separation membrane was developed and used as the substrate via a facile vacuum suction filtration (VSF) method. The microstructure and separation performance of different FO composite membranes were compared and analyzed by SEM, AFM) and FO permselectivity performance test. With the increase of cGO concentration in the coating solution, the WCA of the cGO-coated PSF membrane decreased, accompanied by an increase in water flux. When the cGO concentration was 40 mg L⁻¹, the WCA and pure water flux of the modified PSF membrane can reach 42° and 138.6 L m⁻² h⁻¹, which were 41.0% lower and 69.5% higher than those of the pristine PSF membrane, respectively. The triple-layer water nanochannel architecture, composed of the PA top layer, cGO–PA layer and cGO nanosheet layer, of the FO composite membrane facilitated rapid water longitudinal transport and hence increased the water flux by 60% without weakening the selective separation characteristics (using 0.5 mol L⁻¹ NaCl aqueous solution and pure water as the draw solution and feed solution, respectively). Finally, a three-cycle operation was performed to evaluate membrane durability and the water mass transport model of the cGO-coated FO membrane was proposed.