The electrical interfacial layer at the TiO2 (anatase)/electrolyte interface - Adsorption of Zn(II) and Cd(II) ions

Mechanism of adsorption of Zn(II) and Cd(II) ions at the TiO2 (anatase)/ele ctrolyte interface has been studied by different experimental techniques (p otentiometric titration, microelectrophoresis and adsorption measurements o f zinc and cadmium species). It was found that the point of zero charge (pz c) of anatase (pH = 5.8) was shifted to the lower pH values with increasing concentrations of Zn(II) or Cd(II) ions. The surface charge of anatase in the presence of Zn(II) and Cd(II) for pH > pH(pzc) was higher than that obs erved for original sample in NaClO4 solutions only. Due to low coverage of anatase surface with Zn(II) or Cd(II) species almost no shift of the isoele ctric point (iep) or charge reversal were observed. Adsorption density vs. pH plots for both Zn(II) or Cd(II) showed, typical for multivalent ions, pr esence of ,,adsorption edge."