The isotherms, kinetics and thermodynamics of Cd(II), Zn(II) and Pb(II) biosorption by Penicillium simplicissimum were investigated in a batch system. The effects of pH, initial metal ions concentration, biomass dose, contact time, temperature and co-ions on the biosorption were studied. Adsorption data were well described by both the Redlich-Peterson and Langmuir model. Chemical ion-exchange was found to be an important process based on free energy value from Dubini-Radushkevich isotherm for all metal ions. The results of the kinetic studies of all metal ions at different temperature showed that the rate of adsorption followed the pseudo second-order kinetics well. The thermodynamics constants Delta G degrees, Delta H degrees, and Delta S degrees, of the adsorption process showed that biosorption of Cd(II), Zn(II) and Pb(H) ions on Penicillium simplicissimum were endothermic and spontaneous. (C) 2008 Elsevier B.V. All rights reserved.