Depositing lignin on membrane surfaces for simultaneously upgraded reverse osmosis performances: An upscalable route

Reverse osmosis (RO) have been widely used to produce clean water and there is a strong need to enhance their permeability at no sacrifice of their other performances, e.g., selectivity. We deposit low-cost biopolymer, lignin, onto the surface of RO membranes by a simple filtration method. Lignin is deposited to the membrane surface via both hydrogen bonding and π-π interaction. Lignin deposition reduces the surface roughness of the membrane and enhances its negatively charging, while the surface hydrophilicity is maintained. Surprisingly, water permeation, salt rejection, and fouling resistance of the lignin-deposited membranes are simultaneously improved. More importantly, we demonstrate that this deposition method can be easily extended to modify commercial RO membrane modules, indicating the excellent upscalability of this method. We use the lignin-deposited membranes to treat real effluents of dyeing and papermaking and they perform much better than the virgin, unmodified membranes.