A robust, scalable and adaptive wettability candle soot-modified fiber membrane for controllable oil–water mixtures/emulsion separation

Separation membranes with super-wettability are highly desirable for treating various oil/water contaminants. However, common fiber membranes suffer from single selectivity, poor stability and unsuitable pore structures, which cannot be easily modified to improve their separation performance in practice. Herein, an under-liquid superlyophobic fiber membrane (USFM) was prepared by a two-step approach, namely, spraying candle soot on an electrospun fiber membrane to form a rough structure and subsequently a thermal treatment step to improve stabilities. The obtained USFM-15 exhibits superamphiphilicity in air and under-liquid superlyophobicity after being pre-wetted by water and oil. With the synergy of suitable porosity and high selective wettability, the obtained membrane exhibited permeation fluxes of as high as 22,000 and 56,000 L m-2 h−1 with a separation efficiency of more than 99.5% for immiscible light/heavy oil/water mixtures. The USFM-15 also showed an excellent permeation flux for oil-in-water and water-in-oil emulsions of up to 4,000 and 20,000 L m-2 h−1, respectively. The separation efficiency of USFM-15 for emulsion was still more than 99.2% after 25 cycles. Moreover, the USFM-15 also has excellent reusability, high chemical stability and mechanical durability. The results of this study are expected to provide essential inspiration for designing, developing, and commercializing unique wetting materials.