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 electrophoretic fingerprint is a contour diagram of the observed electrophoretic mobility as a function of the bulk solution pH and plambda, the log of the bulk solution conductivity. Surfactant adsorption was observed to be strong under acidic conditions, as illustrated in the dramatic changes in the electrophoretic fingerprints. Electrokinetic data were compared with adsorption isotherm data obtained by a depletion method and good qualitative agreement was found. The observed pH changes associated with surfactant adsorption suggested ligand exchange as a possible mechanism of adsorption. Electrophoretic fingerprinting was shown to be a powerful means of examining surfactant adsorption to colloidal particles. Copyright 2000 Academic Press.