The structure of the electrical double layer at the titanium dioxide/ethanol solutions interface

Abstract

Results of experiments on surface charge formation in the system monodispersed TiO 2/water or ethanol–water solution of NaCl are presented. The investigations on the solid/water solution of the electrolyte proved that sodium ion adsorption for pH<pH pzc is negligibly small. For NaCl concentrations as low as 0.0001 and 0.001 mol/dm 3 and pH>pH pzc, negative adsorption of Cl − was observed. The above results evidence that the concentration of the surface species, responsible for anion and cation complexity, is negligibly small in the examined range. Potentiometric titrations, ion adsorption and ζ potential measurements in monodispersed TiO 2/ethanol–water and ethanol solution of NaCl were carried out. The presence of ethanol in the solution has no important effect on the acid–basic reactions of surface hydroxide groups in the system, but the adsorption process of background electrolyte ions from ethanol solutions is very complex because it depends on the degree of solvation of both the ions and the oxide surface. The presence of ethanol in the system only slightly decreases the ζ potential and surface charge values in low ionic strength solutions.