Mingxin Zhu,Lijia Liu,Jie Feng,Hongxing Dong,Chunhong Zhang,Fuqiu Ma,Qiang Wang
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.
In this study, hierarchical porous polyacrylonitrile nanofibers were fabricated via electrospinning zeolitic imidazolate framework-8 (ZIF-8) and polyacrylonitrile (PAN), followed by tannic acid (TA) etching and amidoximation (denoted as p-PAN-AO). The as-prepared p-PAN-AO was utilized to remove radioactive U(VI) from sewage water and simulated seawater. The influence of uranium adsorption on p-PAN-AO was investigated as a function of uranium concentration, pH, and time. Adsorption kinetic experiments indicated that the pseudo-second-order kinetic model was fitted better than the pseudo-first-order model. Benefiting from amidoximation and hierarchical porous structure, the nanoadsorbent exhibited a high U(VI) adsorption capacity of 412.28 mg/g at 298 K. The thermodynamic analysis manifested a spontaneous and endothermic nature of U(VI) adsorption. The results demonstrated a potential application of the reported materials in nuclear wastewater and environmental cleanup.
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