Adsorption behavior of antimony(III) oxyanions on magnetite surface in aqueous organic acid environment

Antimony(III) adsorption is observed on magnetite (Fe3O4) surface under acidic and reducing condition through surface hydroxyl (SOH) groups bonding on Fe3O4 surface. Desorption of adsorbed Sb(III) is observed from Fe3O4 surface along with iron release in organic acid at 85 °C after 5 h of experiment. Tartaric acid (TA) shows minimum Sb(III) adsorption on Fe3O4 among the organic acid studied. The reason is TA having two sets of adjacent functional groups viz. OCOH and COH which are responsible for the formation of five-membered bidendate chelate with Sb(III). Other oxyanions, cations or complexing agents along with TA influences the Sb(III) adsorption on Fe3O4. The surface of magnetite is modified by the addition of fatty acids viz. Lauric acid, benzoic acid to bind the SOH groups present on the surface. This results in delaying the process of adsorption without changing the quantity of saturation adsorption of Sb(III) on Fe3O4 surface.

This study describes possible adsorption, dissolution and complexation processes with Sb(III) and Fe3O4 during chemical decontamination.Highlights► Adsorption of Sb(III) on Fe3O4 at low pH occurs with the formation of Fe-O-Sb complex via inner-sphere surface interaction. ► Adsorption Sb(III) on Fe3O4 surface was very low in tartaric acid medium among the verities of organic acids studied. ► The presence of complexing agent phenathroline in tartaric acid medium reduced Sb(III) adsorption further on Fe3O4 surface. ► Adsorption of Sb(III) on Fe3O4 surface increases in the presence of MoO42− and Mn2+ in tartaric acid medium. ► Surface chemical modification of Fe3O4 by Lauric acid or benzoic acid delayed Sb(III) adsorption on magnetite surface.