KINETICS OF CR(III) ADSORPTION-DESORPTION AT THE GAMMA-AL2O3 WATER INTERFACE BY THE PRESSURE-JUMP TECHNIQUE

Mechanistic information regarding Cr(III) adsorption onto gamma-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 gamma-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. (C) 1994 Academic Press, Inc.