Phosphate-based ultrahigh molecular weight polyethylene fibers for efficient removal of uranium from carbonate solution containing fluoride ions

Abstract

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 (DPO, mmol·g−1). UHMWPE-g-PO4 fibers with a DPO of 2.01 mmol·g−1 removed 99.5% of U(VI) from a Na2CO3 solution without the presence of NaF. In addition, when NaF concentration was 3 g·L−1, 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 (Qmax) of UHMWPE-g-PO4 fibers reached 110.7 mg·g−1, which is close to the calculated Qmax (117.1 mg·g−1) 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.