Retention profile of cadmium and lead ions from aqueous solutions onto some selected local solid sorbents

Adsorption of cadmium (Cd2+) and lead (Pb2+) ions on the surface of different samples collected from five regions in Saudi Arabia has been studied. For each experiment, measured amounts of soil (25–300 mg) were shaken with 50 mL of Cd2+ and Pb2+ aqueous solutions. Free Cd2+ and Pb2+ were measured periodically by atomic absorption spectrometer. Varied parameters were pH, initial concentrations, contact time and endogenous ions (Ca2+ and Mg2+). Results indicated that adsorption increases by increasing contact time and initial concentrations. Adsorption was not significant at pHs lower than 6.0 and increases over pH range between 6.0 and 10. Adsorption of Cd2+ and Pb2+ decreases in presence of high concentrations of Ca2+ and Mg2+ which is explained by competitive phenomena between ions on active sites on soil.