Simultaneous alkaline hydrolysis and non-solvent induced phase separation method for polyacrylonitrile (PAN) membrane with highly hydrophilic and enhanced anti-fouling performance

Microporous membranes are now favorably used as a separation tool for the purification of water and wastewater containing fine particles and macromolecular contaminants. However, organic fouling has often become one of the major problems hindering the wider applications of these membranes. In this study, a highly hydrophilic polyacrylonitrile (PAN) membrane with excellent anti-fouling performance was prepared from a method simultaneously combining alkaline hydrolysis and non-solvent induced phase separation (NIPS) processes together. The interplay of the PAN alkaline hydrolysis and NIPS was examined for its effects on both the structural and chemical properties of the prepared membranes. Morphological and porometric analyses confirmed that the new method produced PAN membranes with less macrovoids but highly ordered narrow flow channels in the cross-section structure, as well as a much denser selective surface layer with small and greatly uniform pore sizes. Characterizations in membrane surface wettability and chemical compositions revealed that the new preparation approach can endow the obtained membranes with significantly enhanced surface hydrophilicity as well as oleophobicity within a much shorter preparation time, in comparison with other conventional preparation methods, including the post alkaline hydrolysis of PAN membranes. Filtration experiments for oil (hexadecane)-in-water emulsion, NOM (humic acid) or protein (BSA) solutions have all confirmed that the developed membranes showed remarkably slow flux declining during filtration operation and high flux recovery by simple water flushing for membrane cleaning. Hence, it is anticipated that there is a great potential for the new approach to fabricate anti-fouling PAN membranes, especially for more challenging separation applications in water and wastewater treatment.