Preparation of superamphiphobic composite sponge material with super-wetting reversible switching and application in oil-water separation

The perfluorodecyltrimethoxysilane (PFDMS)-n-decanoic acid (DA)-TiO₂ solution was prepared by a simple sol-gel method, and immersed to obtain the PFDMS-DA-TiO₂ superamphiphobic sponge. Under the induction of ammonia gas with a mass fraction of 25wt%–28wt%, the surface wettability of the PFDMS-DA-TiO₂ sponge is switched from superamphiphobic to superhydrophilic and superoleophobic in air. The surface of the PFDMS-DA-TiO₂ sponge before and after modification was characterized by FTIR and SEM, and its chemical composition and surface morphology were analyzed. The effect of the volume ratio of DA on the reversible switching effect of the PFDMS-DA-TiO₂ superhydrophilic sponge surface infiltration was studied, and its salt tolerance, friction resistance and oil-water separation performance were tested. The results show that the optimal volume ratio of DA is 5.8%. At this time, the oil-water separation efficiency and flux can reach 99.6% and 4775 L/(m²·h), respectively. After the PFDMS-DA-TiO₂ superhydrophilic sponge was subjected to an abrasion test and immersed in 3.5wt% NaCl solution for 12 h, they all exhibit excellent superamphiphobic performance and sponges show high abrasion resistance and salt tolerance. After 20 times of reversibly switching of surface wettability between superamphiphobic and superhydrophobic-superhydrophilic in air induced by ammonia, the two wetting properties can still maintain their own stability, which can be used to effectively separate oil-water mixtures in practical industries.