Ultrafiltration of micellar solutions in the presence of electrolytes

Micellar extraction coupled with ultrafiltration techniques represents a potentially attractive tool for the removal of different kinds of contaminants from waste waters. Even though most industrial streams to be treated contain large amounts of electrolytes, very little is known about the behavior of micellar solutions in ultrafiltration when large amounts of salts are present. This paper is concerned with an investigation of two cationic surfactants (cetyltrimethylammonium bromide (CTAB) and cetylpyridinium chloride (CPC)) and one anionic surfactant (sodium dodecylsulfate (SDS)) in the presence of several salts occurring in specific industrial processes (carbonates and hydrogenocarbonates, nitrites, nitrates). The ultrafiltration behavior of these systems, with individual salt concentrations up to 0.9 M, is studied from the viewpoint of the fluxes obtained, the amount of surfactant leakage and of the membrane ''gel point.'' Two types of polymeric membranes with molecular weight cutoff of 10,000 Da are considered (cellulose and polysulfone), which show significantly different behaviors. (C) 1996 Academic Press, Inc.