Antimony interactions with heterogeneous complexants in waters, sediments and soils: A review of binding data for homologous compounds

Published studies on antimony binding by NOM (natural organic matter) and inorganic colloids are reviewed. Concerning NOM, only complexation by humic-type substances has been studied. Existing data are very limited. Antimony complexation by these substances does not seem to be significant at the pH and concentration levels of surface waters but it might be more important locally in soils where there are higher acidic pH conditions and higher humic concentrations. Binding parameters describing antimony interactions with a variety of inorganic compounds, mainly different types of iron oxides, have been published. Binding is significant at acidic pH values both for Sb(III) and Sb(V) but it decreases abruptly above pH 6-8 in the case of Sb(V). The variety of solid phases, experimental conditions and binding models used so far preclude any comparison between different binders and the use of binding data for accurate quantitative predictions. Different techniques (e.g. Mossbauer spectroscopy, ATR-IR (attenuated total reflection infrared spectroscopy) and XAS (X-ray absorption spectroscopy)) have shown that adsorption of antimony by iron oxides in acidic media takes place via an inner-sphere surface interaction, with the formation of Fe-O-Sb bonds. NOM and mineral surfaces in aqueous systems not only bind metal ions but can also accelerate antimony redox reactions. (C) 2012 Elsevier GmbH. All rights reserved.