Visible light induced self-cleaning ZnO/graphene modified carbon felt with superhydrophilicity and underwater superoleophobicity for on-demand oil-water separation

Rational design of photocatalytic self-cleaning filter materials for oil–water separation is a promising strategy to address performance degradation caused by oil fouling. In this study, graphene (Gr) and Zinc Oxide (ZnO) were assembled on the surface of carbon felt (CF) fibers by electrodeposition and direct precipitation, and thus ZnO/Gr-CF with self-cleaning performance under visible light induction was prepared. On the fiber surface, the multistage micro-nano rough structure formed by micron-sized Gr and scaly ZnO endows the ZnO/Gr-CF with underwater superoleophobicity (153.0°), thereby enabling on-demand oil–water mixtures separation. Additionally, the reduced band gap (2.78 eV) of ZnO/Gr-CF enables its photocatalytic self-cleaning performance under visible light irradiation. The results showed that the ZnO/Gr-CF can achieve high separation efficiency and high flux in separating a variety of immiscible oil–water mixtures (99.8 % and 146169.2 L·m −2 ·h −1 ) and emulsions (98.3 % and 28571.0 L·m −2 ·h −1 ) under gravity-driven. Meanwhile, the ZnO/Gr-CF achieved self-cleaning of oil-fouling, resulting in a Separation Efficiency Recovery Rate (SERR) of 94.6 % and a Flux Recovery Rate (FRR) of 98.8 %. In addition, the ZnO/Gr-CF can separate immiscible and emulsified Degreasing Wastewater (DGW) from AW-Volkswagen, achieving separation efficiencies of 96.0 and 70.8 %, with corresponding flux values of 5425.0 and 4600.0 L·m −2 ·h −1 , respectively. After 50 times separation, the SERR and FRR reached 89.5 and 92.1 %, respectively. Following the water impact, wear resistance, and solvent resistance tests, the underwater oil contact angle of the ZnO/Gr-CF stayed above 150.0°. Self-cleaning filter materials with special wettability provide new insights into the treatment of actual DGW.