Preparation of Phosphoryl-Functionalized Cycas Leaves Fiber Adsorbent and Performance in Uranium Extraction from Seawater

The 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. [Purpose] This study aims to prepare a phosphorus-functionalized Cycas Leaves Fiber-PO4 (P-CLF) with high adsorption performance for uranium in seawater using Cycas Leaves Fiber (CLF) as raw material. [Methods] The 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 were investigated. Meanwhile P-CLF was characterized by Fourier Transform Infrared Spectrometer(FTIR),Scanning electron microscope and Energy Dispersive Spectrometer（SEM-EDS）, and X-ray Photoelectron Spectroscopy (XPS). [Results] The experimental results showed that the optimal pH for P-CLF to adsorb uranium was 5, and the equilibrium adsorption capacity at this pH could reach 1218.05 mg/g, which is one of the best fiber-based adsorbents known so far. After five adsorption-desorption cycles, the adsorption efficiency and desorption efficiency remained at 90.29% and 87.37%, respectively. When eight high-concentration interfering ions were added, the adsorption efficiency of P-CLF for a 5 mg/L uranium solution could reach over 99%. Moreover, the adsorption efficiency for simulated seawater with an initial uranium concentration of 5 mg/L was as high as 97.9%. The characterization results indicated that a large number of phosphate groups with strong coordination ability were successfully introduced onto the surface of P-CLF, and the phosphate groups formed complexes with uranyl ions through the P=O bond and were adsorbed on the surface of the adsorbent. [Conclusions] In conclusion, P-CLF has good recyclability and still 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.