RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

The adsorption mechanism of trivalent Ga and In onto γ-Al₂O₃was investigated using a triple-layer model simulation and pressure-jump technique. Bidentate Ga³⁺and In³⁺and monodentate GaOH²⁺/InOH²⁺are the most likely surface species responsible for Ga(III)/In(III) adsorption. Sorption of Ga(III) and In(III) can be interpreted as an associative process. The adsorption pathway is a two-step mechanism: proton release 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 between the adsorption rate constant and the rate of water exchange, which is developed solely based on the dissociative sorption mechanism of divalent ions.