Arsenic adsorption onto aluminium-substituted goethite

Abstract

Aluminium and iron oxy(hydr)oxides in nature are often partially substituted by the other elements and strongly influence the mobility of arsenic in the environment. Since Because goethite is commonly found in soils, and the oxide is easily substituted, in the presentis work, the adsorption of AsV onto several Al-substituted goethites was explored in order to determine how the substitution affects the adsorption process. Three samples with increasing Al-content (GAl0, GAl3.78 and GAl7.61) were prepared and fully characterised. The variations in AsV adsorption at under different conditions, as well as the variations of the particle surface charge (ZP), were also analysed. The results showed that the removal capacity of Al-goethites is determined by the Al-content. The adsorption maxima per gram followed the trend GAl0> GAl3.78> GAl7.61, indicating that Al-incorporation decreases AsV sorption. The Adsorption per surface area decreased in the order GAl3.78> GAl0> GAl7.61, implying that a small incorporations of Al enhances the adsorption properties of the surface. The stoichiometry of the probable surface complexes formed with the contaminant at different pH values is proposed, by means of the analysis of all the experimental results obtained before and after AsV adsorption. These surface complexes were used to fit the experimental data with a good agreement, and the formation and acidity constants were also estimated.