The biosorption characteristics of antimony(III) from aqueous solution using lichen (Physcia tribacia) biomass was investigated in terms of equilibrium, thermodynamics and kinetics. Optimum biosorption conditions were determined with respect to pH, biomass concentration, contact time, and temperature. Langmuir, Freundlich and Dubinin-Radushkevich (D-R) isotherm models were applied to the equilibrium data. The maximum Sb(III) sorption capacity of P. tribacia was found to be 81.1 mg/g at pH 3, biomass concentration 4 g/L, contact time 30 min, and temperature 20 degrees C. The calculated mean biosorption energy (10.2 kJ/mol) using D-R model indicated that the biosorption of Sb(III) on the biomass was occurred by chemical ion exchange. The highest desorption efficiency (95%) was achieved using 0.5 M HCl. The biosorption capacity of P. tribacia slightly decreased about 10% after ten times of sorption-desorption process. The calculated thermodynamic parameters showed that the biosorption of Sb(III) onto P. tribacia biomass was feasible, spontaneous and exothermic, respectively. The experimental data was also examined using the Lagergren's first-order and pseudo-second-order kinetic models. The results revealed that the pseudo-second-order kinetic model provided the best description of the equilibrium data. (C) 2010 Elsevier B.V. All rights reserved.