Fabrication of ultrafiltration membranes based on methacrylate copolymers containing quaternary ammonium and PEG units for dye removal

Phase inversion involves in a complex process due to numerous factors affecting the membrane formation. Among them, polymer chain entanglement from polymeric membrane materials plays a critical role in regulating membrane structure and is still worth further exploration. Herein, a series of methacrylate copolymers with different contents of poly(ethylene glycol) methacrylate (PEGMA) were designed and synthesized, and ultrafiltration membranes cast from these copolymers were systematically investigated regarding structural evolution and filtration performance. Surface zeta potential of membranes gradually transformed from positive to negative with the increasing PEGMA content due to nonsolvent-induced surface migration of element oxygen, and meanwhile the transformation from finger-like pore structure to sponge-like pore structure in the support layer was observed, which could be attributed to chain entanglement of the PEGMA-rich copolymer. Filtration experiments indicated that sponge-like membranes possessed better separation effect of Victoria blue B compared with finger-like membranes, and the optimized mPP40-15 % showed a retention rate of 99.55 % and permeance of 110.26 L m−2 h−1 bar−1 and displayed good selective separation of dye/salt mixture. Besides, sponge-like membranes also exhibited easy regeneration, anti-fouling property and filtration stability. This work will provide guidance for modulating membrane structure and offer an alternative material for membrane separation in handling dye wastewater.