The biosorption characteristics of As(III) and As(V) from aqueous solution using the macrofungus (Inonotus hispidus) biomass were investigated as a function of pH, biomass dosage, contact time, and temperature. Langmuir, Freundlich and Dubinin-Radush kevich (D-R) models were applied to describe the biosorption isotherm of the metal ions by I. hispidus biomass. Langmuir model fitted the equilibrium data better than the Freundlich isotherm. The biosorption capacity of I. hispidus for As(III) and As(V) was found to be 51.9 mg/g and 59.6 mg/g, respectively at optimum conditions of pH 6 for As(III) and pH 2 for As(V), contact time of 30 min and temperature of 20 degrees C. The metal ions were desorbed from I. hispidus using both 1 M HCl and 1 M HNO3. The high stability of I. hispidus permitted 10 times of adsorption-elution process along the studies with a decrease about 11-28% in recovery of As(III) and 10-25% for As(V). The mean free energy values evaluated from the D-R model indicated that the biosorption of As(III) and As(V) onto I. hispidus biomass was taken place by chemical ion-exchange. The calculated thermodynamic parameters showed that the biosorption of As(III) and As(V) ions onto L hispidus biomass was feasible, spontaneous and exothermic under examined conditions. Kinetic examination of the experimental data were showed that the biosorption processes of both As(III) and As(V) followed well pseudo-second-order kinetics. (C) 2008 Elsevier B.V. All rights reserved.