Sorption of antimony (V) onto synthetic goethite in carbonate medium

Abstract

The sorption kinetics of antimony(V) on synthetic goethite is very fast compared to the sorption of other metals on goethite (e.g. arsenic and selenium) and depends on temperature, with an activation energy of 49+9 kJ . mol21 in the temperature range 15–358C. Sorption isotherms have been developed at different temperatures and ionic strength values. The results have been modelled using a Langmuir isotherm and there is not a considerable influence of neither the temperature in the range studied (158C–358C), nor the ionic strength (between 0.001 and 0.01 mol . dm23). Sorption is very high at pH values lower than 8, at more alkaline pH, the sorption decreases with pH, as expected considering the Antimony(V) predominating complex in solution, Sb(OH)6 2. Triple-layer model successfully describes the data obtained by assuming a bidentate edge-sharing surface complex of antimonate on the surface of goethite.