New Antifouling and Antibacterial Membrane Material for Highly Selective Removal of Nitrate and Phosphate

To remove nitrate and phosphate from sewage efficiently, current membranes need improved permselectivity, antifouling, and antibacterial properties. Herein, a new hybrid membrane modified with quaternary ammonium and silanol groups was fabricated by doping siloxane quaternary ammonium loaded activated carbon (SiQA) onto poly(vinylidene fluoride) (PVDF). The hybrid membranes had surface morphology, porosity, membrane pore sizes, and water fluxes typical of ultrafiltration membranes. At a secondary sewage effluent flux of 35 LMH, the permeate nitrate and total phosphorus concentrations were <1 mg-N L–1 and <0.2 mg-P L–1, respectively. Superior removal selectivity of nitrate and phosphate was attributable to the introduced positively charged quaternary ammonium groups. Improved hydrophilicity from silanols reduced irreversible membrane fouling by 67% compared to a nondoped membrane. The quaternary ammonium groups also increased antibacterial activity. The antifouling and antibacterial hybrid membrane overcomes the permeability–selectivity trade-off and may be applicable in advanced sewage treatment.