The Removal of Arsenic and Uranium from Aqueous Solutions by Sorption onto Iron Oxide-Coated Zeolite (IOCZ)

In this study, an iron oxide-coated zeolite (IOCZ) nanocomposite was synthesized and used for the removal of U(VI) and As(III) from aqueous solutions using a batch system. Parameters such as various contact times, pH, competing ions (Cd2+, Co2+, and Cr3+), temperature, and initial concentrations of uranium(VI) and arsenic(III) were investigated. The experimental results were fitted to the Langmuir, Freundlich, and Dubinin–Radushkevich isotherms to obtain the characteristic parameters of each model. Results suggested that adsorption of U(VI) and As(III) by IOCZ was best modeled with the Freundlich isotherm. The kinetic experimental data fitted the pseudo second-order model better than the pseudo first-order model for both elements. Using the thermodynamic equilibrium constants obtained at different temperatures, various thermodynamic parameters, such as ΔGo, ΔHo, and ΔSo, were calculated. These parameters indicated that the process is spontaneous and exothermic in nature. It was noted that an increase in temperature resulted in a decrease of 8.5 and 27.5% for U and As removal, respectively. An increase in initial concentrations of U(VI) and As(III) from 10 to 100 mg L−1 at pH 3 resulted in increased adsorption capacities (qe) for both elements. The increases were from 1.247 to 20.10 mg g−1 for U(VI) and from 3.115 to 54.18 mg g−1 for As(V). The presence of competing ions such as Cd2+, Co2+, and Cr3+ enhanced the removal of As by 9.2% whereas the adsorption capacity of uranium decreased by 13.8%. This research demonstrated that IOCZ is a potential adsorbent for the removal of U(VI) and As(III) from aqueous solutions.