Self-oxidation cycle of oxidized red phosphorus for regeneration of binding sites enables efficient uranium extraction in tributylphosphate-kerosene system

Abstract

Photocatalytic extraction of hexavalent uranium (U(VI)) is challenging in organic phase, especially the widely used tributylphosphate (TBP)-kerosene system in the nuclear fuel cycle process. Organic components in TBP-kerosene system are difficult to be oxidized, which limits the reduction of U(VI). Herein, we demonstrated a self-oxidation strategy to enable the photocatalytic cycle of U(VI) reduction in TBP-kerosene system by the deeply oxidized commercial red phosphorus (DO-CRP). In the 30 %TBP-kerosene solution, the DO-CRP exhibited 88.0 % of extraction efficiency with 580.8 mg/g of capacity for U(VI) within 120 min. In this process, PO43− groups generated at the defects were used as the binding sites to capture and reduce U(VI). Following desorption process involved in the cleavage of uranium and PO43− groups, which released defect sites for self-oxidation in the next cycle. Mechanistic study revealed that such regeneration of self-oxidation and U(VI) binding sites achieved the continuous photocatalytic extraction of U(VI) in TBP-kerosene system.