Fabrication of ultra-smooth thin-film composite nanofiltration membrane with enhanced selectivity and permeability on interlayer of hybrid polyvinyl alcohol and graphene oxide

Nanofiltration (NF) membranes prepared by conventional interfacial polymerization (IP) method still have relative low water flux. This paper reports a kind of high-flux, ultra-thin and ultra-smooth thin-film nanocomposite (TFN) NF membranes by IP reaction with both low concentration of piperazine (PIP) and trimesoyl chloride (TMC) on the surface of a tailor-made hydrophilic interlayer. This interlayer, which was made of polyvinyl alcohol (PVA)-modified graphene oxide (GO) and was followed by further glutaraldehyde post-crosslinking, greatly helps to manipulate the IP reaction, remarkably decrease the skin layer thickness (down to 15 nm) and roughness (down to 5 nm), and increase apparently the separation performance of the TFN NF membrane. Under optimal conditions (PVA concentration of 1.0 wt%, GA concentration of 1.0 wt% and GO concentration of 10 mg L−1), the fabricated TFN NF membrane has a relative high water permeance (158 L m−2 h−1 MPa−1), an extremely high Na2SO4 rejection (99.7%), an extremely high separation factor (230) of Na2SO4 to NaCl among those of the membranes with Na2SO4 rejection higher than 98%, as well as greatly enhanced fouling resistance and chlorine resistance. The much superior advantages of the prepared TFN NF membrane over most of the state-of-the-art literature works demonstrate its vast potential in industrial separation and purification of aqueous electrolytes or organic solute solutions.