ADSORPTION MECHANISM OF GALLIUM(III) AND INDIUM(III) ONTO GAMMA-AL2O3

The adsorption mechanism of trivalent Ga and In onto gamma-Al2O3 was i nvestigated using a triple-layer model simulation and pressure-jump te chnique, Bidentate Ga3+ and In3+ and monodentate GaOH2+/InOH2+ are the most likely surface species responsible for Ga(III)/In(III) adsorptio n, Sorption of Ga(III) and In(III) can be interpreted as an associativ e process, The adsorption pathway is a two-step mechanism: proton rele ase from surface hydroxyl group(s) followed by coordination of Ga(III) /In(III) species to the depronated site(s), Intrinsic adsorption rate constants cannot be estimated with a liner free-energy relationship be tween the adsorption rate constant and the rate of water exchange, whi ch is developed solely based on the dissociative sorption mechanism of divalent ions. (C) 1997 Academic Press.