Use of polyelectrolyte-surfactant complexes in colloid-enhanced ultrafiltration

Water-soluble polyelectrolyte-surfactant complexes, involving oppositely charged species, can form at quite low thermodynamic activities of the surfactant. This fact can be exploited in colloid-enhanced ultrafiltration separations, where both molecular organic pollutants and toxic ions are to be removed from contaminated aqueous streams. Investigations have been made of (a) the solubilization and ultrafiltration of solutions of organic solutes in polymer-surfactant solutions, for comparison with studies of micellar surfactant solutions in the absence of added polymers; (b) the penetration of surfactant through the membrane (leakage of monomer) in dialysis and ultrafiltration experiments; and (c) the utility of polyelectrolytes as 'scavengers' for surfactant species that enter the permeate or filtrate in colloid-enhanced ultrafiltration separations. Polyelectrolytes chosen for the studies are sodium poly (styrenesulfonate) and poly (dimethyldiallylammonium chloride); the surfactants are cetylpyridinium chloride (hexadecylpyridinium chloride) and sodium dodecylsulfate. A detailed study has been made of the solubilization and separation of p-tert-butylphenol in aqueous mixtures of sodium poly(styrenesulfonate) and cetylpyridinium chloride, at polyelectrolyte to surfactant mole ratios of two to one.