Evaluation of copper removal efficiency using water treatment sludge

Large quantities of sludge are produced during water treatment processes. Recently, sludge has been treated as waste and disposed of in landfills,which increases the environmental burdens and the operational cost. Therefore, sludge reuse has become a significant environmental issue. In this study, adsorption of copper ions(Cu) onto calcined sludge was investigated under various operational conditions(with varying temperature, Cuinitial concentration, pH, and sludge dosage). The prepared sludge material was characterized with transmission electron microscopy(TEM), X-ray diffraction(XRD), dynamic light scattering(DLS), and Brunauer-Emmett-Teller(BET) surface area. The sorption capacity of sludge was directly proportional to the initial Cuconcentration and inversely proportional to the sludge dosage. The optimum operational pH and solution temperature were 6.6 and 80℃, respectively. The experimental results followed a Langmuir isotherm and pseudo-first-order adsorption kinetics.Thermodynamic parameters such as activation energy, change in free energy, enthalpy, and entropy were calculated. Thermodynamic analyses indicated that the sorption of copper ions onto the calcined sludge was driven by a physical adsorption process. The prepared sludge was proven to be an excellent adsorbent material for the removal of Cufrom an aqueous solution under optimum conditions.