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.