Adsorption of copper(II) onto sewage sludge-derived materials via microwave irradiation

Abstract

The materials with adsorbent properties were produced from urban sewage sludge by two different procedures via microwave irradiation: (1) by one single pyrolysis stage (SC); (2) by chemical activation with ZnCl(2) (SZ). The BET, SEM and FT-IR have been used to evaluate the pore structural parameters and surface chemistry of the adsorbents, respectively. Subsequently they were used for adsorption of Cu(II) from aqueous solutions. The effects of various experimental parameters, such as pH, temperature were investigated in a batch-adsorption technique. The results showed that the adsorption of Cu(II) was maximal at pH 5.0. The kinetic study demonstrated that the adsorption process was followed the second-order kinetic equation. The experimental adsorption isotherm data were well fitted with Langmuir model and the maximum adsorption capacity of Cu(II) were found to be 3.88 and 10.56 mg/g for SC and SZ, respectively, in the solution of pH 5.0. Thermodynamic parameters such as changes in the enthalpy (ΔH(0)), entropy (ΔS(0)) and free energy (ΔG(0)) indicate that Cu(II) adsorption onto SC and SZ is an endothermic and spontaneous process in nature at 15-45°C. These results indicate that the sewage sludge-derived material via microwave induced ZnCl(2) activation is an effective and alternative adsorbent for the removal of Cu(II) from aqueous solution.