The biosorption of Cu(II) and Pb(II) ions from aqueous solutions by dried activated sludge was investigated as a function of initial pH, initial metal ion concentration and temperature. The results showed that both the heavy metals uptake processes followed the pseudo-second-order equation. The equilibrium data fitted very well to both Langmuir and Freundlich adsorption models. The main mechanism of Cu(II) and Pb(II) biosorption on dried activated sludge was their binding with amide I group. (C) 2005 Elsevier Ltd. All rights reserved.