The adsorption characteristics of C.I. Reactive Orange 16 (RO 16) from aqueous solution onto residual brewery yeast were investigated under various experimental conditions. At pH 3.0 and 308 K, the adsorption capacity of RO 16 onto residual brewery yeast was found to be 0.56 mol/kg. Experimental data indicated that the adsorption capacity of residual brewery yeast for the dye was higher in acidic, than in neutral or basic solutions. The adsorption equilibrium data showed good correlation with the Langmuir isotherm models. The estimated values for the free energy of adsorption (Delta G degrees) were -6.661, -4.812 and -3.929 kJ/mol at 288, 298 and 308 K, respectively, which indicated that a spontaneous process had occurred. The negative values of enthalpy (Delta H degrees) and entropy (Delta S degrees) indicated the exothermic nature of the adsorption of RO 16 onto residual brewery yeast. Kinetic studies showed that the biosorption of RO 16 onto residual brewery yeast in the system followed pseudo-second order kinetics. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B. V. and The Society of Powder Technology Japan. All rights reserved.