Recovery of uranium ions from simulated seawater with palygorskite/amidoxime polyacrylonitrile composite

A polyacrylonitrile/palygorskite composite chemically modified with amidoxime groups was prepared by free-radical graft polymerization of acrylonitrile onto 3-glycidyloxypropyl trimethoxy silane (KH-560)-modified palygorskite and characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Adsorption of uranium(VI) from simulated seawater on the material was investigated. Batch experiments were carried out to study the effects of initial pH, contact time, initial feed concentration and ionic strength on uranium removal. The solution pH values had a major impact on uranium(VI) adsorption with optimal adsorption observed around pH   5. The kinetic data followed the pseudo second-order process. The equilibrium data fitted the Freundlich model well and the maximum adsorption capacity was found to be 78.13   mg/g. The ionic strength did not significantly affect uranium removal and chemisorption was assumed to describe the uranium adsorption. Desorption was performed using 0.1   M HCl solution, and the regenerated adsorbents could be reused with little loss of adsorption capacity after five cycles.