Mixed adsorption of a non-ionic and an anionic surfactant at the carbon–aqueous solution interface

Abstract

Adsorption from mixed aqueous solutions of sodium dodecyl sulphate and O-n-octyltetraethylene glycol on to graphitised carbon has been determined by solution depletion. A decrease in total adsorption was found in comparison with the amount expected from isotherms for separately adsorbed surfactants. An extension of the Rubingh theory for mixed-micelle formation is proposed to allow deviations from non-ideal mixing in the adsorbed layer to be specified. Application of the theory indicates positive deviations from ideal mixing for the system studied.