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

Results of experiments on surface charge formation in the system monodisper sed TiO2/water or ethanol-water solution of NaCl are presented. The investi gations on the solid/water solution of the electrolyte proved that sodium i on 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 neglig ibly small in the examined range. Potentiometric titrations, ion adsorption and zeta potential measurements in monodispersed TiO2/ethanol-water and et hanol solution of NaCl were carried out. The presence of ethanol in the sol ution has no important effect on the acid-basic reactions of surface hydrox ide groups in the system, but the adsorption process of background electrol yte ions from ethanol solutions is very complex because it depends on the d egree of solvation of both the ions and the oxide surface. The presence of ethanol in the system only slightly decreases the zeta potential and surfac e charge values in low ionic strength solutions. (C) 1999 Elsevier Science B.V. All rights reserved.