Surface modification of TFC FO membrane using N-isopropylacrylamide (NIPAM) to enhance fouling resistance and cleaning efficiency

Poly(N-isopropylacrylamide) (PNIPAM) was grafted onto the surface of commercially available thin film composite (TFC) forward osmosis (FO) membranes via radical graft polymerization at alkaline conditions to improve organic fouling resistance and cleaning efficiency. The successful grafting of PNIPAM to TFC membranes was confirmed using attenuated total reflectance–Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy, and the grating time for the modification of membrane surface was optimized by monitoring and evaluating peak intensities of the spectroscopies. PNIPAM-grafted membranes exhibited improved resistance to organic fouling compared with the neat membranes when exposed to a synthetic wastewater containing high concentration of alginate foulants. Furthermore, PNIPAM-grafted membrane showed higher cleaning efficiency resulted from the structure transition of PNIPAM-grafted polymers between 25°C and 50°C cleaning solutions. These results indicate that the application of thermo-responsive polymers to FO membranes can improve fouling resistance and cleaning efficiency during the desalination process.