Modification of ultrafiltration membrane by thermo-responsive Bentonitepoly(N-isopropylacrylamide) nanocomposite to improve its antifouling properties

Stimuli responsive materials have attracted extensive attention as promising candidates for fouling surface of membranes. Therefore, we investigated the performance of a simple and environmentally friendly method for fouling phenomenon in ultrafiltration membranes that does not have limitations of other cleaning method (e.g. chemical cleaning method). In this method, firstly, the surface of Bentonite (BNT) nanoparticle was organomodified by 3-methacryloxypropyltrimethoxysilane (MPS) and then the Potassium Persulfate (KPS) is utilized as an initiator to react with n-isopropyleacrylamid to introduce thermo-responsive characteristic to BNT surface via free radical polymerization. Afterwards, a series of BNT-PNIPAAm nanocomposite membranes was fabricated. Infrared spectroscopy (IR) results indicated the successful polymerization of NIPAAm on BNT surface. Also, the thermogravimetric analysis (TGA) showed that BNT-PNIPAAm nanocomposite was thermally less stable than the bare BNT. Moreover, the thermo-responsiveness of BNT-PNIPAAm nanocomposites was confirmed by Dynamic Light Scattering (DLS) technique. The thermo-responsive behavior of the prepared membrane was studied via the adsorption/desorption behavior of bovine serum albumin (BSA) on the membrane surface. According to the dynamic filtration result, the membrane containing BNT-PNIPAAm nanocomposite exhibited better water flux performance. By applying thermo-responsive cleaning method for membrane cleaning, the membrane with 0.5 wt% of BNT-PNIPAAm nanocomposite displayed higher flux recovery (more than 95 %) under the 1000 ppm skim milk solution, whereas, the unmodified membrane was recovered approximately 40 %. The thermo-responsive membrane has greater performance compared to its conventional counterpart with respect to their nonmobility nature.