Sustainable superwetting membrane for effective separation of oil–water emulsion and dye removal

Water pollution from organic oily solvents and dyes is a major global problem. While some wettable materials exist for oily pollutants, few can effectively separate different oil–water emulsions and dyes. To address this problem, we developed a smart citric acid-crosslinked bamboo powder-coated membrane (CBM) with approprite surface roughness and switchable wettability. The CBM membrane is superhydrophobic in oil and superoleophobic in water, making it highly effective in separating oil–water emulsions and dyes. The membrane can efficiently separate various oil–water emulsions, including crude oil-in-water emulsions, with a separation efficiency of 99.76 % and a high flux of 1756 L/m²/h. It also adsorbs anionic (e.g. Congo red) and cationic (e.g. methylene blue) dyes in wastewater, with an adsorption rate of 99.45 % after multiple cycles. The membrane can simultaneously separate oil-in-water emulsions and remove dyes from water, facilitating high-value utilization of biomass waste and offering great promise for addressing global water pollution from oily organic solvents and dyes.