Removal of Cu and Pb ions from aqueous solutions by electric furnace slag: Kinetic and thermodynamic aspects

Abstract

Electric furnace slag, instead of deposition as a non-toxic metallurgical waste material, can be used as a valuable secondary raw material in many industrial processes. In this paper, removal of copper and lead ions from aqueous solutions by sorption on electric furnace slag (EFS) has been investigated. Experiments were performed at three temperatures of 23, 40 and 55ºC. The results of sorption kinetics are tested by kinetic model that describes intraparticle diffusion, and diffusion coefficients have been calculated. Diffusion rate of both systems increases with temperature, in dependence of time is constant for copper ions, while for lead decreases. The energy of activation (Ea), activation enthalpy (ΔH*), activation entropy (ΔS*) and free energy of activation (ΔG*) have been calculated based on kinetic data. Values of Ea characterize binding of lead and copper ions on EFS as activated chemisorption, whereas positive values of ΔH*, ΔG* and negative values of ΔS* describe process as endothermic, nonspontaneous and without changes in the structure of the solid particle. The studies showed that this low cost waste material could be used as an efficient sorbent material for the removal of lead and copper from aqueous solutions.