The unique size-dependent properties of nano-objects make them valuable building blocks for creating advanced chemical systems, facilitating breakthroughs in different areas. In pervaporation, composite
membranes with a thin selective nano-sized layer are being actively developed, allowing a highly efficient separation of different mixtures. In this study, highly efficient composite membranes were developed by creation
of a thin dense selective layer from polyelectrolyte complex (PEC) from sodium alginate (SA) and polyethylenimine (PEI). Composite PEC membranes were prepared by three methods: (1) physical adsorption, (2) by layer-by-layer (Lbl) technique and (3) in a dynamic mode. The structure of the thin selective layer of
membranes were studied by scanning electron (SEM) and atomic force (AFM) microscopies. The physical adsorption method is the most effective for obtaining highly efficient composite membranes from PEС: 0.05–1.18 kg/(m2h) permeation flux and more than 95 wt % water in the permeate in pervaporation dehydration of ethanol (4–70 wt % water).