Adsorption of sodium dodecyl sulfate to colloidal titanium dioxide: An electrophoretic fingerprinting investigation

The adsorption of sodium dodecyl sulfate to colloidal titanium dioxide was investigated using the electrophoretic fingerprinting approach. An electrop horetic fingerprint is a contour diagram of the observed electrophoretic mo bility as a function of the bulk solution pH and p lambda, the log of the b ulk solution conductivity. Surfactant adsorption was observed to be strong under acidic conditions, as illustrated in the dramatic changes in the elec trophoretic fingerprints. Electrokinetic data were compared with adsorption isotherm data obtained by a depletion method and good qualitative agreemen t was found. The observed pH changes associated with surfactant adsorption suggested ligand exchange as a possible mechanism of adsorption. Electropho retic fingerprinting was shown to be a powerful means of examining surfacta nt adsorption to colloidal particles. (C) 2000 Academic Press.