ADSORPTION OF COPPER AND ZINC FROM AQUEOUS SOLUTIONS USING FULLER’S EARTH: KINETICS, EQUILIBRIUM, AND THERMODYNAMICS

Abstract

Heavy metals are non-biodegradable toxins that can accumulate in nature. Many of the most widespread heavy metals are copper and zinc. Adsorption is an effective method for the uptake of heavy metals from wastewater. Thus, this research aimed to study the adsorption of copper and zinc onto fuller’s earth. The effects of the solution’s pH and initial concentration were investigated. The results showed that the efficiency of removal increased with the initial pH value of the solution. The optimum initial concentration of either copper or zinc for maximum removal efficiency was found to be 100 mg/L. The adsorption kinetics and mechanism were studied using pseudo-first-order, pseudo-second-order, Elovich equation, intra-particle, and Boyd models. The data were best fitted with a pseudo-second-order kinetic model for either copper or zinc concentrations. The data were also fitted using several isotherms for equilibrium studies, such as Langmuir, Dubinin-Radushkevich, Freundlich, and Temkin. The adsorption of either copper or zinc using fuller’s earth was best fitted with a Dubinin-Radushkevich and Temkin isotherm, respectively. Thermodynamics and desorption studies were also reported. The results indicate that the adsorption efficiency increased with temperature, while desorption studies showed that HCl was able to regenerate the used fuller’s earth. Finally, the morphology of the fuller’s earth before and after adsorption was examined and showed the difference between the surfaces of fuller’s earth before and after adsorption process.