Surfactant and cosurfactants in lamellar liquid crystals and adsorbed on solid surfaces: II. Influence of electrolyte on the model system sodium dodecyl sulphate/benzyl alcohol and α-alumina

Abstract

The adsorption of sodium dodecyl sulphate (SDS) and benzyl alcohol (BzOH) onto solid Al 2O 3 from aqueous solutions has been studied at varying contents on NaCl. A fixed amount of SDS at the saturation adsorption level of SDS (5 × 10 −2 M) was chosen. The adsorption of both SDS and BzOH was found to increase with increasing salinity. At high electrolyte content a considerable amount of alcohol is located in the adsorbed phase. Calculations of the individual area requirements of the SDS and BzOH molecules in the adsorbed state was undertaken and values of 0.40 and 0.24 nm 2 were obtained for the SDS and BzOH, respectively. Parallels are drawn to the packing of the studied surfactant and alcohol in the lamellar lyotropic crystalline D phase in the same model system without electrolyte.