On the mechanistic modeling of As(III) adsorption on gibbsite

Arsenite adsorption on gibbsite was examined as a function of pH, ionic strength (I) and contact time (t(C)). As(III) showed a weak affinity for gibbsite surface. The trends of pH = f (Gamma(ads)) curves have showed a marked deviation from a typical anion adsorption edge showing a maximum Gamma(ads) around pH similar to 8.2. The experimentally derived proton exchange ratio has always converged to zero when 0.26 < Sigma[As(III)] < 7 muM and 6.2 < pH < 8.2. The isosteric heat of adsorption, DeltaH(r), exhibited invariant behavior with respect to Gamma(ads). The As(III) adsorption data was quantified by charge distribution multi-site complexation (CD MUSIC) model using the surface complex postulated below: [GRAPHICS] (C) 2003 Elsevier Science Ltd. All rights reserved.