Study of the adsorption of Cd and Zn onto an activated carbon:: Influence of pH, cation concentration, and adsorbent concentration

The single adsorption of Cd and Zn from aqueous solutions has been investigated on Scharlau Ca 346 granular activated carbon in a wide range of experimental conditions: pH, metal concentration, and carbon concentration. The results showed the efficiency of the activated carbon as sorbent for both metals. Metal removals increase on raising the pH and carbon concentration, and decrease on raising the initial metal concentration. The adsorption processes have been modeled using the surface complex formation (SCF) Triple Layer Model (TLM). The adsorbent TLM parameters were determined. Modeling has been performed assuming a single surface bidentate species or an overall surface species with fractional stoichiometry. The bidentate stoichiometry successfully predicted cadmium and zinc removals in all the experimental conditions. The Freundlich isotherm has been also checked.