Optimization of lead (II) biosorption in an aqueous solution using chemically modified aerobic digested sludge.

Biosorption of Pb(II) by using digested sludge obtained from a municipal wastewater treatment plant in Tehran was examined. The aims of this investigation were biosorption of Pb(II) ions onto chemically treated digested sludge with hydrogen peroxide (H₂O₂) solution and determination of kinetic and isotherm of biosorption. Biosorption capacity of two types of sludge (treated and untreated) for biosorption of Pb(II) ions was investigated as function of initial Pb(II) concentration and pH using batch biosorption systems. The equilibrium biosorption capacity increased with increasing of initial metal ion concentrations and pH for both of digested sludge. The pseudo-second order kinetic model was found to be slightly suitable than the pseudo-first order kinetic model to correlate the experimental data for two types of digested sludge (R²>0.9). Regarding the applicability of the isotherm models, the freundlich model was found to be suitable than the other isotherm models. According to obtained q(max) from Langmuir isotherm, biosorption of Pb(II) by H₂O₂ treated digested sludge was found to perform better than untreated digested sludge. The maximum biosorption capacity was given 185.19 and 144.93 mgg⁻¹ for H₂O₂ treated and untreated digested sludge, respectively. Also, the constant of energy (B) between the Pb(II) ions and the adsorbent surface, calculated using BET isotherm model, obtained 5401 and 3401 for H₂O₂ treated and untreated digested sludge, respectively. These results indicate the usefulness of H₂O₂ treated digested sludge as a biosorbent for Pb(II) biosorption.