SURFACE COMPLEXATION ON TIO2 .1. ADSORPTION OF H+ AND CU2+ IONS ONTO TIO2 (ANATASE)

Studies of the adsorption and desorption of H+ ions and the adsorption of Cu2+ ions on TiO2 (anatase) were made by alkali-metric titration i n 0.1 M (K)NO3 solutions at 298.2 K using ion-selective electrodes and atomic absorption spectrometry. The adsorption is explained in terms of surface-complex formation. The active surface groups were defined a s multifunctional sites consisting of bridged and terminal hydroxyl gr oups. With help of the computer program ''GRFIT,'' a model for the sor ption behavior was designed. The surface potentials were accounted for by the constant capacity approximation. The experimental results are explained by the general equilibria >S + pH(+) + qCu(2+) = > SHpCuq(p2q+); beta(p,q,(int))(S) = [>SHpCuq(p+2q+)]/ [>S][H+](p)[Cu2+](q) e((p +2q)F Psi/RT)) where >S denotes the neutral surface sites, and the sta bility constants log beta(1,0,(int))(S) = 5.40, log beta(1,0,(int))(S) = -7.75, log beta(-2,0,(int))(S) = -17.21, log beta(0)(S),(1,(int)) = 4.76, log beta(-1,1,(int))(S) = 1.13, log beta(-2,1,(int))(S) = -6.74 .