Mechanistic Insights of a Thermoresponsive Interface for Fouling Control of Thin-Film Composite Nanofiltration Membranes

In spite of extensive research, fouling is still the main challenge for nanofiltration membranes, generating an extra transport resistance and requiring a larger operational pressure in practical applications. We fabricated a highly antifouling nanofiltration membrane by grafting poly(N-isopropylacrylamide) (PNIPAM) chains on a bromine-containing polyamide layer. The resulting membrane was found to have a double permeance compared to the pristine membrane, while the rejection of multivalent ions remained the same. In addition, PNIPAM chains yielded a better deposition resistance and adhesion resistance, thereby mitigating the increase of fouling and promoting the recovery of flux during the filtration and traditional cleaning stages, respectively. Moreover, PNIPAM chains shrank when the water temperature was above the lower critical solution temperature (LCST), indicating the formation of a buffer layer between the membrane and pollutants. The buffer layer would eliminate the membrane–foulant interaction energy, thus further enhancing the detachment of pollutants. This simple and efficient cleaning method could act as an enhanced cleaning procedure to remove irreversible fouling. This provides new insights into the fabrication of enhanced antifouling membranes using smart responsive polymer chains.