An Ethanol/Ammonia Dual-Responsive Membrane for Separating Complex Emulsions via Vapor Stimulation

Oily wastewater, with its complex composition, is creating a growing demand for smart materials with tunable wettability that can adapt to changing environmental conditions. However, their practical application in oil–water separation is still limited by issues such as long response time and operational complexity. An ethanol/ammonia dual-responsive mixed cellulose ester membrane was prepared by grafting SiO2 with fluorocarbon molecules (FS-61). Through inducing the polar hydrophilic groups (−COO–) and nonpolar oleophobic groups (−C6Fx) by ammonia and ethanol, the FS@SiO2 membrane achieves a switchable wettability: initially superhydrophilic, turning hydrophobic (WCA: 142°) upon ethanol exposure, and reverting to superhydrophilic after ammonia stimulation, with stable reversibility over several cycles. The wettability transition enables the membrane to separate complex oil–water mixtures, including interface oil and emulsions, utilizing ethanol and ammonia as wettability triggers. For the emulsions, after 10 cycles, the separation efficiency remained at 98.76% (oil-in-water) and 97.95% (water-in-oil). These findings provide a crucial theoretical foundation and technical support for the development of highly efficient and tunable oil–water separation materials, while also paving the way for solutions to treat complex oil–water mixtures such as industrial oily wastewater and marine oil spills.