Application of a Greek zeolite embedded with Fe-oxyhydroxides for uranium retention from aqueous solutions

Abstract A natural, HEU-type zeolite embedded with Fe-oxyhydroxides was prepared by a simple and fast precipitation method. The natural and treated sorbents were characterized by a variety of methods including X-Ray Diffraction, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy and BET surface area, revealing the amorphous nature of the oxyhydroxides consisting of ferrihydrite and poorly crystalline goethite. The interactions of the sorbents with uranium aqueous solutions under varying conditions were subsequently investigated. Iron oxyhydroxide deposition enhanced the sorption properties of the natural zeolite (from 194.6 to 237.9 mg g –1 at pH 4) while parameters such as pH, initial metal concentration, and presence of competing ions (Na + , Ca 2+ ) as background electrolytes greatly affected the sorption capacities. Results from the materials characterization before and after sorption accompanied by fitting the experimental isothermal and kinetic data to mathematical models as well as thermodynamic calculations, showed that the sorption was due to a combination of surface complexation and ion exchange processes. Desorption and leaching tests provided insight into the influence of iron oxyhydroxides on uranium sorption behavior.