Removal of Co²⁺, Ni²⁺, and Pb²⁺ by Manganese Oxide-Coated Zeolite: Equilibrium, Thermodynamics, and Kinetics Studies

Abstract

Abstract The removal of Co 2+ , Ni 2+ , and Pb 2+ from aqueous solutions using a modified zeolite was investigated because of the need to eliminate toxic contaminants from wastewaters. In the present study the ways in which equilibrium, thermodynamics, and kinetics parameters affected the removal of heavy metals were evaluated and compared. An Iranian clinoptilolite with a Si/Al ratio of 6.5 was used as an adsorbent. In order to increase the adsorption capacity of the adsorbent, it was converted to a manganese oxide-coated zeolite (MOCZeo) using various Mn solutions. The initial concentration of metals, pH, contact time, and temperature were the variables studied and optimal conditions were established. The maximum amount of Co 2+ , Ni 2+ , AND Pb 2+ adsorption on MOCZeo was ascertained. A thermodynamics study, using Δ G , Δ H , and Δ S state functions showed that adsorption of Pb 2+ was more spontaneous than that of Co 2+ , Ni 2+ ions. The adsorption of these ions on MOCZeo was an endothermic reaction. Investigation of the adsorption models revealed that the adsorption of Pb 2+ , Co 2+ , and Ni 2+ on MOCZeo followed both the Langmuir and Freundlich models. Kinetics studies showed that the adsorption of Pb 2+ , Co 2+ , and Ni 2+ on MOCZeo followed the pseudo-second order kinetics model with a high correlation coefficient.