Performance design of a highly anti-fouling porous membrane with dual pH-responsiveness

With the increasingly extensive application of membrane technology, facing the wastewater system with complex components, it is urgent to develop a porous membrane with excellent pollution-resistant and easily cleaned after pollution. Herein, a membrane with dual pH-responsiveness effects was successfully fabricated via a facile and eco-friendly method. The isoelectric point of zeta potential of the modified membrane (M-D-IA) appeared at pH = 4.31. It exhibited positive-charged and the water intake rate reached 427% under strongly acidic conditions, while it showed negative-charged with the water intake rate reaching 492% under strongly alkaline conditions, showing an excellent dual pH-responsiveness. Meanwhile, the membrane M-D-IA possessed good super-hydrophilic and underwater super-oleophobic surface characteristics. Furthermore, the membrane M-D-IA displayed an excellent oil-fouling resistance in the treatment of hexadecane/water mixed emulsion, with the water flux decay rate (FDR) only 17.5% after 7 cycles of operation and the water flux recovery rate (FRR) remained above 99.7% after alkali cleaning. Notably, the membrane M-D-IA also had excellent dual pH-responsiveness when treating typical polluted wastewater HA/CaCO3 feed solution. The FRR was as high as 98.3% after washing with alkali and acid solution in turn, indicating that the membrane not only possessed a significant resistance to organic/inorganic pollution but also had an outstanding recovery of membrane flux after cleaning. Moreover, the water flux of the membrane M-D-IA was maintained at 850 L m−2 h−1 during 30 days of storage, displaying an excellent resistance to biological pollution. [Display omitted] •PVDF-CTFE membrane with dual pH-responsiveness was successfully fabricated.•Super-hydrophilic and underwater super-oleophobic endowed the membranes with excellent anti-fouling performance.•The dual-charge characteristic played a synergistic role in the process of cleaning.•The M-D-IA possessed excellent anti-bacterial property, retarding membrane bio-fouling during use.