Engineering hydrophobic membranes with tunable pore accessibility via selective swelling of SDS block copolymers for ethanol concentration

The separation of ethanol from dilute aqueous solutions, such as fermentation broths, is critically important for biofuel production. Membrane distillation (MD) with porous membranes usually suffers from insufficient selectivity, while pervaporation (PV) with dense films is inadequate in permeability. To overcome this trade-off, we developed a novel hydrophobic membrane via the selective swelling of a polystyrene- b -polydimethylsiloxane- b -polystyrene triblock copolymer (SDS). By precisely controlling the swelling agent and duration, we engineered the optimal membrane with a tailored pore structure featuring interconnected nanopores and partially blind pores, along with a PDMS-enriched pore surface. This unique architecture enables a multipath permeation mechanism combing solution-diffusion and the transport pathway for molecules under vapor–liquid equilibrium within pore channels. The optimized membrane demonstrated an exceptional combination of high permeation flux and separation factor for a 5 wt% ethanol/water mixture at 50 °C, yielding a remarkable pervaporation separation index (PSI) of 38.2 kg·m −2 ·h −1 . This performance surpasses many PDMS-based PV and conventional MD membranes. This work presents a simple and efficient strategy for fabricating high-performance membranes that simultaneously achieve high flux and selectivity, offering significant potential for advancing energy-efficient bioethanol recovery processes.