Kinetic Model of Arsenic Sorption onto Zero-Valent Iron (ZVI)

This study investigated the mechanisms involved in removing arsenic from water using zero-valent iron (ZVI) as sorbent. Relatively limited information is available on the kinetics aspects of sorption of arsenic compounds onto ZVI. In order to gain an understanding of the sorption kinetics, a detailed study was conducted in a controlled batch test and developed sorption kinetic model. The effects of different arsenic concentrations on the kinetics sorption rates of arsenic(V) and arsenic(III) were investigated. Arsenic(V) was removed by two mechanisms-surface adsorption and co-precipitation with Fe(III) on ZVI, while arsenic(III) was removed by adsorption on ZVI and oxidized to arsenic(V). Reaction rate constants were calculated for arsenic(V) and arsenic(III) at different concentrations by a second-order kinetic model. The results indicate that ZVI could be employed as sorbent materials to enhance the adsorption and co-precipitation processes to improve the removal rate of arsenic from water. The results also showed that the arsenic(III) oxidized to arsenic(V), while the analyses indicated that there was no measurable reduction of arsenic(V) to arsenic(III).