Efficient uranium adsorption by amidoximized porous polyacrylonitrile with hierarchical pore structure prepared by freeze-extraction

Abstract An efficient uranium adsorbent, amidoximated polyacrylonitrile foam (AOPAN) with a hierarchical pore structure, was prepared by freezing-extraction followed by amidoximation. AOPAN was analyzed by Fourier transform infrared (FT-IR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), and showed an excellent uranium adsorption performance in aqueous solutions; the uranium adsorption capacity was 1058 mg/g. Even in the presence of competing ions, AOPAN showed a high selective removal ability for uranium (removal rate > 85%). After three cycles, the adsorption capacity and removal rate for uranium were still higher than 800 mg/g and 90%, respectively, which indicated the good recyclability of AOPAN. Furthermore, the adsorption process fitted the Freundlich model and the pseudo-second-order kinetic model. The calculated ΔH° and ΔG° indicated that the adsorption process was endothermic. The higher adsorption temperature could promote the adsorption on AOPAN. The XPS analysis indicated that the chelation between the amidoxime group and uranium plays a key role in the adsorption of uranium on AOPAN.