RES³T - Rossendorf Expert System for Surface and Sorption Thermodynamics

Mechanistic information regarding Cr(III) adsorption onto γ-Al₂O₃ was obtained using the triple layer model (TLM) in conjunction with experimental data gathered using the pressure-jump technique. Adsorption data and TLM simulation results suggest the formation of both mono- and bidentate inner-sphere Cr³⁺ or CrOH²⁺ complexes at the surface of γ-Al₂O₃. The mechanism of Cr(III) sorption was interpreted as proton release from surface hydroxyl group(s) followed by the attachment of Cr³⁺ or CrOH²⁺ to form bidentate (SO)₂Cr⁺ and monodentate SOCrOH⁺. The binding constant of Cr³⁺ or CrOH²⁺ with deprotonated reacting site(s) simulated using the TLM and equilibrium sorption data was in excellent agreement with that determined from kinetic results, verifying the proposed reaction mechanisms.