Effect of Performance and Fouling Mechanisms of Thermo-Responsive Membranes on Treating Secondary Effluent Containing Added Sulfamethoxazole

Wastewater treatment plants generally lack a specialized design for the efficient removal of sulfamethoxazole (SMX), a toxic and bio-resistant compound. In this study, secondary effluent from a Beijing wastewater reclamation treatment plant was spiked with SMX and used to investigate the filtration performance and fouling mechanisms of thermo-responsive membranes. Thermo-responsive materials were prepared using polyvinylidene fluoride, N-isopropylacrylamide (NIPAM), and graphene oxide through Ce (IV)-induced redox radical polymerization. The results showed that the removal of SMX and COD reached 42% and 92%, respectively, with a NIPAM dosage of 1 g, and the removal of UV254 reached its highest value at 57.9%. Additionally, the filtration flux was higher at a temperature of 35 °C with a NIPAM dosage of 1 g. The fluorescence intensity of the organic matter from the secondary effluent spiked with SMX and decreased after the thermo-responsive membranes were implemented, and filtration with the membrane containing 1 g of NIPAM achieved a lower intensity at a value of 3074.6, according to the analysis of three-dimensional fluorescence excitation–emission spectroscopy. According to the extended Derjaguin–Laudau–Verwey–Overbeek theory analysis, the interfacial free energies of the thermo-responsive membrane with a 1 g dose of NIPAM were higher than the others during filtration.