Phosphate-Based Ultrahigh Molecular Weight Polyethylene Fibers for Efficient Removal of Uranium from Carbonate Solution Containing Fluoride Ions

This work provides a cost-effective approach for preparing functional polymeric fibers used for removing uranium (U(VI)) from carbonate solution containing NaF. Phosphate-based ultrahigh molecular weight polyethylene (UHMWPE-g-PO₄) fibers were developed by grafting of glycidyl methacrylate, and ring-opening reaction using phosphoric acid. Uranium (U(VI)) adsorption capacity of UHMWPE-g-PO₄ fibers was dependent on the density of phosphate groups (D , mmol∙g ). UHMWPE-g-PO₄ fibers with a D of 2.01 mmol∙g removed 99.5% of U(VI) from a Na₂CO₃ solution without the presence of NaF. In addition, when NaF concentration was 3 g∙L , 150 times larger than that of U(VI), the U(VI) removal ratio was still able to reach 92%. The adsorption process was proved to follow pseudo-second-order kinetics and Langmuir isotherm model. The experimental maximum U(VI) adsorption capacity (Q ) of UHMWPE-g-PO₄ fibers reached 110.7 mg∙g , which is close to the calculated Q (117.1 mg∙g ) by Langmuir equation. Compared to F , Cl , NO₃ , and SO₄² did not influence U(VI) removal ratio, but, H₂PO₄ and CO₃² significantly reduced U(VI) removal ratio in the order of F > H₂PO₄ > CO₃² . Cyclic U(VI) sorption-desorption tests suggested that UHMWPE-g-PO₄ fibers were reusable. These results support that UHMWPE-g-PO₄ fibers can efficiently remove U(VI) from carbonate solutions containing NaF.