Preparation of phosphoryl-functionalized cycas leaves fiber adsorbent and performance in uranium extraction from seawater

BackgroundThe uranium reserves in seawater are approximately 4.5 billion tons, but extracting 1 kg of uranium from seawater requires processing about 300 million liters of seawater. Therefore, how to prepare adsorption materials that can maintain high adsorption capacity, long-term stability, and specific selectivity for uranium in the complex seawater environment is an urgent problem to be solved in the field of uranium extraction from seawater.PurposeThis study aims to prepare a phosphorus-functionalized Cycas Leaves Fiber-PO4 (P-CLF) with high adsorption performance for uranium in seawater using CLF as raw material.MethodsThe CLF was chemically modified with phosphate to prepare the P-CLF, and the effects of initial pH, temperature, contact time, initial concentration, and adsorbent dosage on the adsorption of uranium from seawater by P-CLF were experimentally investigated. Meanwhile P-CLF was characterized in experiments by Fourier Transform Infrared Spectrometer (FTIR), Scanning Electron Microscope and Energy Dispersive Spectrometer (SEM-EDS), and X-ray Photoelectron Spectroscopy (XPS).ResultsThe experimental results show that the optimal pH for P-CLF to adsorb uranium is 5, and the equilibrium adsorption capacity at this pH could reach 1 218.05 mg·g-1, which is one of the best fiber-based adsorbents known so far. After five adsorption-desorption cycles, the adsorption efficiency and desorption efficiency remain at 90.29% and 87.37%, respectively. When eight high-concentration interfering ions are added, the adsorption efficiency of P-CLF for a 5 mg·L-1 uranium solution could reach over 99%. Moreover, the adsorption efficiency for simulated seawater with an initial uranium concentration of 5 mg·L-1 is as high as 97.9%. The results show that a large number of phosphoric acid groups with strong coordination ability are successfully introduced onto the surface of P-CLF. The phosphoric acid groups coordinate with uranyl ions through the P=O bond to form complexes that are adsorbed on the surface of P-CLF.ConclusionsResults of this study demonstrate that P-CLF has good recyclability and exhibits excellent uranium adsorption performance in high-salt, high-pH, and high-concentration ion interference environments, showing practical application potential in the field of uranium extraction from seawater.

研究背景：海水中的铀储量约为45亿吨，但从海水中提取1千克铀需要处理约3亿升海水。因此，如何制备能够在复杂海水环境中保持高吸附容量、长期稳定性以及对铀的特异性选择性的吸附材料，是海水提铀领域亟待解决的关键问题。
研究目的：本研究以苏铁叶纤维（Cycas Leaves Fiber, CLF）为原料，制备一种对海水中铀具备高吸附性能的磷功能化苏铁叶纤维-磷酸酯（P-CLF）。
实验方法：本研究通过磷酸酯对CLF进行化学改性以制备P-CLF，并通过实验考察了初始pH值、温度、接触时间、初始浓度及吸附剂投加量对P-CLF吸附海水中铀的影响。同时，采用傅里叶变换红外光谱仪（Fourier Transform Infrared Spectrometer, FTIR）、扫描电子显微镜-能谱仪（Scanning Electron Microscope and Energy Dispersive Spectrometer, SEM-EDS）以及X射线光电子能谱（X-ray Photoelectron Spectroscopy, XPS）对P-CLF进行了表征。
实验结果：实验结果表明，P-CLF吸附铀的最优pH值为5，该条件下的平衡吸附容量可达1218.05 mg·g⁻¹，为目前已知性能最优的纤维基吸附剂之一。经过五次吸附-解吸循环后，吸附效率与解吸效率分别维持在90.29%和87.37%。当添加八种高浓度干扰离子时，P-CLF对5 mg·L⁻¹铀溶液的吸附效率可达99%以上。此外，对初始铀浓度为5 mg·L⁻¹的模拟海水的吸附效率高达97.9%。进一步分析证实，大量具备强配位能力的磷酸基团被成功引入P-CLF表面，这些磷酸基团通过P=O键与铀酰离子配位形成络合物并吸附于P-CLF表面。
研究结论：本研究结果表明，P-CLF具备良好的可回收性，在高盐、高pH值及高浓度离子干扰环境中均表现出优异的铀吸附性能，在海水提铀领域展现出实际应用潜力。