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.