The biosorption of Au(III) from an aqueous solution using Bacillus subtilis was investigated under various experimental conditions: pH, biomass concentration, contact time and temperature. The optimum pH value was determined to be 2.0, and Au(III) uptake reduced with the increase of temperature to within the range of 298-323 K. Au(III) adsorption proceeded very rapidly in the first 10 min and subsequently tended to achieve equilibrium. Au(III) biosorption was found to better fit the Freundlich model, and the Freundlich model provided a maximal Au(III) uptake capacity at 355 mg/g for B. subtills. Moreover, a pseudo-second-order kinetic model provided a better correlation for the experimental data. The thermodynamic parameters free energy (Delta G degrees), enthalpy (Delta H degrees) and entropy (Delta S degrees) were then calculated from an obtained experimental data source, which revealed this biosorption to be exothermic and spontaneous. Finally, Fourier transform infrared (FT-IR) spectroscopy examined the functional groups that might participate in the interaction between Au(III) and B. subtilis. which illustrated that the working functional groups were the amino, carboxyl and hydroxyl groups. These results indicate that B. subtilis can be used as an effective biosorbent to remove Au(III) from an aqueous solution. (C) 2011 Elsevier B.V. All rights reserved.