EQUILIBRATION OF KAOLINITE IN AQUEOUS INORGANIC AND SURFACTANT SOLUTIONS

Equilibration of a natural kaolinite sample and its purified sodium form in water and aqueous solutions of NaCl and sodium dodecyl benzenesulfonate (SDDBS) and sodium dodecyl sulfonate (SDDS) involves a fast ion-exchange and/or electrostatic adsorption step and a slow step possibly due to dissolution of aluminum species upon prolonged contact of kaolinite with water. Equilibration processes were found to depend on ionic strength, pH, and treatment of the sample. Past studies using kaolinite appear not to have considered the possibility of an intermediate metastable condition which could be responsible for a number of contradicting results found in the literature. Examination of results obtained for the sulfonate under various ionic strengths and hydrogen ion concentrations suggests a complex adsorption mechanism involving ion-exchange, electrostatic, metal activated modes of adsorption and precipitation depending on the solution pH. © 1979.