Effect of clay colloids on the zeta potential of Fe/Al oxide-coated quartz: a streaming potential study

Purpose This study was conducted in order to examine the effect of colloidal particles on electrochemical properties of charged larger size materials. Materials and methods A self-made streaming potential apparatus was used to measure the zeta potentials of Fe/Al oxide-coated quartz. The effects of colloidal particles of kaolinite and montmorillonite on the electrochemical properties of Fe/Al oxide-coated quartz were investigated through comparing the difference in zeta potential of the coated quartz in electrolyte and clay suspension. Results and discussion The change of zeta potentials of the coated quartz, when clay suspensions flowed through, increased with the increasing concentrations of kaolinite and montmorillonite and degree of coating with Fe/Al oxides, and decreased with increased ionic strength of the suspensions. Electrostatic attraction between clay colloids and the coated quartz was the key factor influencing the interaction between the oppositely charged particles. The deposition of colloidal particles of kaolinite and montmorillonite on coated quartz and the overlapping of the diffuse layers of electrical double layers between the oppositely charged particles were responsible for the change in zeta potential of Fe/Al oxide-coated quartz. The relative contribution of the deposition of clay particles to the change in zeta potential was greater than that of the overlapping of diffuse layers. Conclusions When clay suspensions flowed through the saturated sand of Fe/Al oxide-coated quartz, both overlapping of diffuse layers between charged sand and clay particles and deposition of clay particles contributed to change of zeta potential of the coated quartz.