Facile preparation of antifouling nanofiltration membrane by grafting zwitterions for reuse of shale gas wastewater

Complex organic matter causes severe fouling when membranes are applied for shale gas wastewater (SGW) treatment. This study reports the grafting of a zwitterionic polymer brush consisting of poly (sulfobetaine methacrylate) (PSBMA) onto the surface of a commercial nanofiltration (NF) membrane via electron transfer-atom transfer radical polymerization (ARGET-ATRP) to achieve anti-fouling property, especially against organic foulants. Compared to the pristine NF membranes, the PSBMA-grafted NF membrane showed high performance when challenged by SGW as a feed stream: (1) The flux stability was significantly improved during long-term operation, with a 64.28% increase in flux normalization at 50% recovery rate of SGW, while maintaining a suitable initial flux and near constant ion removal rate; (2) Based on excitation-emission-matrix spectra integrated in the fluorescence region, the removal of protein-like organic matters and humus-like organic matters increased by 34% and 16.5%, respectively; (3) The XDLVO theory supports the hypothesis that the hydrophobic interactions between the membrane surface and organic foulants were reduced by enhancing the Lewis acid-base interaction energy. The proposed anti-fouling zwitterionic membranes has potential in industrial application for the on-site reuse of SGW.