Robust underwater superoleophobic membranes with bio-inspired carrageenan/laponite multilayers for the effective removal of emulsions, metal ions, and organic dyes from wastewater

Oil spills, especially high-viscous oil, are a major environmental threat due to their high adhesive nature, which can lead to the easy fouling of filtration membranes. Superhydrophilic membranes fabricated from bioinspired materials with superior wettability behavior are considered effective in removing soluble/insoluble organic pollutants from water. For efficient antifouling and oil-water separation, materials designed using hydrogels forming species with low-adhesive superoleophobicity may be more suitable; however, controlling the hydrogel thickness and the membrane pore size is difficult. Herein, we report a simple approach to fabricate bio-inspired underwater superoleophobic membranes via the treatment of hydrolyzed polyacrylonitrile (h-PAN) membranes with naturally obtained ĸ-carrageenan (CGN) and a nanoclay laponite. A layer-by-layer (LbL) deposition technique applied to yield self-assembled membranes with nanosized pores, high flux, and efficient underwater superoleophobic properties along with high contact angles for oils due to the high surface functional groups. The laponite/CGN modified membranes exhibited excellent adsorption of water-soluble dyes with high stability and flexibility. Complete metal-ion removal could be achieved from contaminated water by passing through a simple filtration process in addition to the removal of oils and soluble dyes. We believe that the reported modified membranes can serve as excellent candidates for underwater superoleophobic applications and removal of organic pollutants from water.