Preparation of fouling-resistant and self-cleaning PVDF membrane via surface-initiated atom transfer radical polymerization for emulsified oil/water separation

This research describes the modification of polyvinylidene fluoride (PVDF) ultrafiltration membranes by grafting poly (N-isopropylacrylamide) using surface-initiated atom transfer radical polymerization (SI-ATRP) in order to detach adhered foulants during oily water filtration. The preparation of self-cleaning ultrafiltration membranes for oily water treatment has not received much attention in the literature. Field emission scanning electron microscopy (FESEM), attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and water contact angle were used to characterize the structure of membranes. ATR-FTIR spectroscopy verified the grafting of PNIPAAm from the membrane surface. Membrane performance was investigated by water flux measurement using deionized water and synthetic oily water. The water flux was obviously higher than that of commercial PVDF membrane at different temperatures. Moreover, PNIPAAm concentration and polymerization time were used to optimize the performance of the grafted membranes. N-isopropyl acrylamide at a concentration of 1.33 mol/L and 30 h reaction time were found as the best condition for ATRP process in this study. The irreversible fouling ratio was only 4.46 % and the maximum of flux recovery ratio was 95.53 % (after cold water rinse), which was obtained for the modified membrane at the best condition. These results show that modified membranes have excellent antifouling property. Grafted membranes also exhibited good oil rejection (95.2 %). Therefore, these easily cleanable membranes could be used to effectively separate emulsified oils from water at different temperatures.