Removal of Zn 2+ , Cd 2+ and Pb 2+ from binary aqueous solution by natural zeolite and granulated activated carbon

Abstract

The adsorptive removal of Zn 2+ , Cd 2+ and Pb 2+ from single and binary metal ion aqueous solution using natural clinoptilolitic zeolite tuff, a regional low-cost naturally available adsorbent, and granulated activated carbon, an adsorbent conventionally applied in wastewater treatment, was studied. The competitive adsorption equilibrium of three binary mixtures (Cd 2+ /Zn 2+ , Zn 2+ /Pb 2+ and Pb 2+ /Cd 2+ ) with different ratios of initial metal ion concentrations, on both adsorbents, was determined in batch mode at 25 oC. Langmuir and Freundlich isotherms were used to interpret the adsorption data of the investigated systems. The results indicate that the Langmuir isotherm fits the data better in both single and binary component systems. Natural zeolite and granulated activated carbon showed similar adsorption capacity for Pb 2+ , although granulated activated carbon had higher adsorption capacity for Zn 2+ and Cd 2+ than natural zeolite. The order of metal ion selectivity on both adsorbents is Pb 2+ > Cd 2+ > Zn 2+ . The binary equilibrium of adsorption showed competitive nature. For all studied metal ions (Zn 2+ , Cd 2+ and Pb 2+ ) the natural zeolite and granulated activated carbon metal ion adsorption capacity in the case of binary systems (adsorption) are lower than those obtained for a single metal systems (adsorption), and are significantly influenced by the ratios of initial metal ion concentrations in the binary water solutions.