Asymmetric Wettability Channel of Membranes for Water and Oil Concurrent Recovery from Emulsions
Conventional oil-water separation technologies, including centrifugation and flocculation, suffer from density-dependent limitations and secondary pollution, while membrane filtration with uniform wettability selectively recovers only one phase, leaving retained components unrecovered. Janus membranes with asymmetric wettability enable on-demand separation but their micro/nanoscale thickness restricts interfacial separation to microscopic domains. This work presents a Janus-channel-membrane (JCM) architecture that scales asymmetric wettability from micro/nanoscale to millimeter-scale spatial channels, constructed from a hydrophilic membrane and a hydrophobic membrane separated by a slit of a few millimeters. When surfactant-stabilized emulsions are delivered to the slit, purified water permeates rapidly through the hydrophilic membrane while oil is concurrently recovered at the hydrophobic membrane. The millimeter-scale channel width enhances enrichment and collision behavior of emulsion droplets via interference interactions between the membrane pair, producing substantial increases in oil and water recovery rates. The JCM demonstrates distinctive advantages for separating and recovering both phases from high-concentration-surfactant-stabilized emulsions. Multistage device configurations incorporating JCMs can further strengthen separation and recovery efficiency at multiple levels, offering transformative potential for industrial emulsion separation and recovery. This spatial configuration of membranes with contrary wettability at the millimeter scale addresses key bottlenecks in concurrent oil and water recovery from stable emulsions.