Dehydration of organics by pervaporation with polyelectrolyte complex membranes: Some considerations concerning the separation mechanism

Polyelectrolyte complex (PELC) membranes were prepared by simultaneous interfacial reaction of aqueous solutions of two oppositely charged poly-ions, i.e. from cellulose sulfate and various polycations as well as a cationic surfactant. Pervaporation investigations proved that such membranes prepared with polycations may be successfully used for dehydration of various organic solvents. Measurements of swelling and pervaporation properties of model membranes confirm, that the anionic polysaccharide Na-cellulose sulfate is the only component responsible for good separation capability in dehydration of organics with PELC membranes. Water molecules we assume to be preferentially transferred from one hydrogen bonding site to another across the polysaccharide chains. We can conclude that not the sorption into the upstream surface, but the diffusion selectivity along a swelling gradient across the stabilized cellulose sulfate mainly governs the separation behaviour.