Bio-inspired catalytic one-step prepared R-siloxane cellulose composite membranes with highly efficient oil separation

Inspired by the hydrophobic waxy layer structure on the back of the desert beetle, a super-hydrophobic material was prepared via the sol–gel silanisation of porous cellulose membrane (CM) using triethoxysilanes with different carbon chain lengths (R-siloxane) and (CH3CH2O)4Ti as a catalyst in 3 min. The R-siloxane CM was both super-hydrophobic and oleophilic (water contact angle (CA) > 150°, dodecane CA ≈ 0°) and resisted liquids with surface tensions as low as 15 mN·m−1, correlated with the length of the R-siloxane and roughness of the CM. Instructed by the water collection behavior of the desert beetle, a pristine filter CM was added on the R-siloxane filter CM to accelerate separation of Span 80–stabilised water-in-oil emulsions by generating a surface energy gradient (SEG). The composite membrane with SEG separated the emulsions with higher surfactant concentrations and provided a higher efficiency up to 99.98% compared with single-layer R-siloxane membrane. This bio-inspired catalytic one-step approach for preparing R-siloxane cellulose composite membranes can potentially replace petroleum-based products for oil purification.Graphical AbstractBio-inspired preparation of R-siloxane composite cellulose membrane with surface energy gradient for highly efficient water-in-oil emulsion separation.