In this study, the biosorption of anionic Sb(OH)(6)(-) by chemically modified biomass of cyanobacteria Microcystis from Taihu Lake was investigated and the possible mechanisms were discussed. Acid treatment using 0.1 mol/L HCl significantly enhanced the biosorption as compared with the original biomass. The biosorption for both the original and acid-treated biomass decreased with the increase of pH with the optimal range being pH 2.5-2.6. The biosorption processes obey the Freundlich isotherm model. The reusability experiments demonstrated a desirable regeneration performance for both the original and acid-treated biomass in the repetitive biosorption-desorption cycles. However, the acid treatment resulted in higher biosorption capacities than the original biomass in the first three cycles. The results of zeta potential and ATR-IR suggest that the binding of Sb(OH)(6)(-) on the biomass occurred through electrostatic attraction and complexation. The ATR-IR spectra further confirmed the involvement of amino, carboxyl and hydroxyl groups in the removal of Sb(OH)(6)(-). SEM-EDXA analyses indicate that the biosorption was highly heterogeneous. There was no change in the valence state of Sb(V) observed from the XANES spectra of Sb L edge for the biosorbed biomass. This study suggests promising biosorption potential of Microcystis to remove Sb(V) from wastewater. (c) 2011 Elsevier B.V. All rights reserved.