Bioinspired engineering protein nanofibrils-based multilayered self-cleaning membranes for universal water purification.

Proteinaceous materials are promising for membranes due to greater mechanical strength, in-built functionalities, amphiphilicity and high molecular loading capacity. Herein, a novel strategy of functionalization of silk nanofibrils with metal oxyhydroxide and fabrication of ultrafast permeable multi-layered and self-cleaning membrane was demonstrated. Typically, 1.9 µm thick multilayered membrane efficiently purifies macromolecules, dyes, pharmaceutical, surfactants and oil-water emulsion contaminated wastewater with rejection rate > 89% with the flux rate > 883 Lmh. Further, the potential of the multilayered membrane was tested for series of different feed concentrations of fluoride and As (V) to validate the commercial applicability of the multilayered membranes for industry wastewater. Notably, even at higher concentration of 10-30 mgL, >96% for fluoride and >87% for As (V) rejection was obtained. Furthermore, the functionalized multilayered membrane exhibited outstanding performance for fluoride removal in real water streams, where, it purifies approximately 4710 L.m in two consecutive cycles, before the quality of the effluents no longer meets WHO criteria. However, the remarkable separation efficiency principally attributed to adsorption sites on the surface of the membrane. Thus, various regeneration strategies were established based on the nature of pollutants. More importantly, photocatalytic Fenton-like reaction assisted self-cleaning property of the multilayered membrane is demonstrated for regeneration of organic fouled membrane. Overall, the present multilayered membrane exhibits superior performance in purifying organic, inorganic contaminated water and oil-water emulsion with excellent recyclability; hence, envisaged its application for Universal water purification.