INTERACTION OF TRANSITION-METAL IONS WITH HYDROUS TIN(IV) OXIDE SURFACE

The interaction of transition metal ions with hydrous SnO2 surface has been investigated by measuring the amount of H+ released from the oxide and the amount of metal ions adsorbed on the oxide surface. Aqua ions Cu2+, Co2+, Ni2+ and Mn2+ enhanced the amount of H+ released from SnO2, whereas stable complex ions such as [Fe(phen)3]2+ and [Co(en)3]2+ had very little interaction with the oxide. The relation between the amount of H+ released and that of metal ion adsorbed, and the pH-dependence of the relation suggest that the surface interaction is the coordination reaction of aqua-metal ions with the deprotonated surface sites formed in acid-base reactions of SnO2. The experimental data on the surface complex formation indicate that two surface species are formed with stoichiometric ratios (the deprotonated site/metal ion) of 1 : 1 and 2:1. A correlation was found between the formation constants of the surface complexes and the corresponding values for hydroxo complexes of metal ions. © 1979, The Chemical Society of Japan. All rights reserved.