Insights into boosting SiC membrane superhydrophobic-superoleophilic property and oil purification performance by hierarchical structure control

Engineering of superhydrophobic-superoleophilic (SHB-SOL) ceramic membrane surface with hierarchical structures remains challenging and the relation between physicochemical structure-dependent wettability and separation performance lacks investigation. Herein, SHB-SOL SiC ceramic membranes with different hierarchical micro-nano structures were fabricated by ZnO nanoflower (NF) deposition and silane grafting. Three SiC ceramic membranes with different pore sizes were purposefully used as the pristine, these membranes displayed similar geometric structures in different scales. The modified SiC membrane surface becomes stronger in SHB-SOL property as the pore size decreases and the optimal membrane possessing the lowest pore size presented a water contact angle of 172.46° and a water sliding angle of 5°. When used for pure oil or oily mixture separation, all the SHB-SOL SiC membranes exhibited enhanced oil fluxes compared with their pristine forms. At a pressure of 0.5 bar, the optimal membrane could completely reject water droplets and graphite solids (D50 =4.8 µm) for the oil-water-solid mixture containing 0.05 wt% water and 0.05 wt% graphite, showing a stable oil (hexane) flux of 1383.8 L·m−2·h−1. This work also reveals the effects of the hierarchical structures on the SHB-SOL property formation and the resulting antifouling mechanism, which offers novel insights into boosting ceramic membranes with desired surface wettability for enhanced separation performance.