Porous Bacterial Cellulose Janus Membranes for Oil–Water Separation

Abstract Porous Janus membranes with asymmetric wettability for efficient oil–water separation are reported. Porous scaffolds consisting of bacterial cellulose (BC) or composites of BC and poly(vinyl alcohol) (PVA–BC) were modified by spin-coating one side with poly(butylene succinate) (PBS) as a hydrophobic barrier layer and carboxymethylation (CM) of the opposite side to enhance surface wettability. Optimized process conditions afford membranes with a superhydrophilic CM side, displaying water contact angles below 5° and underwater–oil contact angles above 117°, and a hydrophobic PBS side with a water contact angle of approximately 90°. The membranes promote high oil–water separation fluxes of 1.0–1.8 × 104 L·m–2·h–1·MPa–1 and separation efficiencies greater than 99.9% for a range of oil types. Importantly, the membrane components─BC, PBS, and optionally PVA─are biodegradable and, in the case of BC and PBS, biobased. Our results demonstrate a sustainable, easily accessible, high-performance Janus membrane platform that combines excellent separation efficiency with environmentally benign materials, highlighting its potential for practical oil–water separation applications.