Pervaporation dehydration of ethanol by hyaluronic acid/sodium alginate two-active-layer composite membranes

•Two-active-layer composite membranes were prepared by sequential spin-coating.•Sorption and diffusion behavior in capping layer and inner layer were studied.•Positioning of HA layer and NaAlg layer in membrane affected separation factor.•HA/Alg/PAN membrane exhibited higher pervaporation performance. The composite membranes with two-active-layer (a capping layer and an inner layer) were prepared by sequential spin-coatings of hyaluronic acid (HA) and sodium alginate (NaAlg) on the polyacrylonitrile (PAN) support layer. The SEM showed a mutilayer structure and a distinct interface between the HA layer and the NaAlg layer. The coating sequence of two-active-layer had an obvious influence on the pervaporation dehydration performance of membranes. When the operation temperature was 80°C and water concentration in feed was 10wt.%, the permeate fluxes of HA/Alg/PAN membrane and Alg/HA/PAN membrane were similar, whereas the separation factor were 1130 and 527, respectively. It was found that the capping layer with higher hydrophilicity and water retention capacity, and the inner layer with higher permselectivity could increase the separation performance of the composite membranes. Meanwhile, effects of operation temperature and water concentration in feed on pervaporation performance as well as membrane properties were studied.