Adsorption equilibrium isotherms of Pb2+ , Ni2+ And Cd2+ onto Powdered egg shells

Abstract

This study reports the adsorption equilibrium of lead (Pb²⁺), nickel (Ni²⁺) and cadmium (Cd²⁺) from aqueous solution by chicken's eggshells. The eggshells were collected from within Obafemi Awolowo University, Ile-Ife, Nigeria. They were washed with distilled water, air dried, pulverized, sieved into different particle sizes and stored for use. The properties of the powdered eggshells (PES) were determined. The PES was used as an adsorbent to remove Pb²⁺  , Ni²⁺  and Cd²⁺  from aqueous solution on a single and multi-component systems basis and from raw water as well as wastewaters in a batch process. Effects of initial concentration of the metals, pH of the solution and particle size of PES on the adsorption capacities of the selected metals onto the PES were monitored. The study revealed that the PES contains calcium, aluminum, and iron as part of its major components. Adsorption capacities for Pb²⁺ , Ni²⁺  and Cd²⁺  onto the PES were 89.4 % ,70.6 % and 89.4 % respectively for mono-components synthetic wastewaters, but dropped to 80 %, 62.3 % and 36.8 % for Pb²⁺  , Ni²⁺  and Cd²⁺ respectively when used for multi-component systems (raw water). There were slight reductions in the adsorption of Pb²⁺  , Ni²⁺  and Cd²⁺  onto larger particle size of the PES. Adsorption capacities were higher when initial concentrations were higher. Adsorption equilibrium isotherms and their parameters were not affected significantly by changes in pH of the solution and particle size of the PES and fitted adequately into different adsorption equilibrium isotherms. Estimated cost of the PES production was found to be lower (0.43USD) than the cost of producing other adsorbents. It was concluded that the PES could be a suitable adsorbent to remove Pb²⁺  , Ni²⁺  and Cd²⁺  from aqueous solutions.

 Keywords: Adsorption, Powdered eggshells, Heavy Metal Removal, Synthetic Wastewaters, Raw Water, Isotherms, Adsorption Parameters.