Quaternary Phosphonium-Grafted Porous Aromatic Framework for Preferential Uranium Adsorption in Alkaline Solution

Abstract

Uranium, as an energy source and radioactive waste, is very important in the nuclear fuel cycle. Recovery of uranium from nuclear waste solution is essential for further treatment and disposal. Herein, an ionic liquid-functionalized porous aromatic framework material P–C4 (PPN-6-CH2P+(C4H9)3Cl–) for uranium adsorption from alkaline solution was synthesized by grafting PPN-6 with the quaternary phosphonium for the first time. The U-exchange kinetics perfectly conforms to the pseudo-second-order dynamic model, which reveals the chemical adsorption process. P–C4 exhibits a record high uranium exchange capacity of over 670 mg/g and can efficiently capture [UO2(CO3)3]4– ions in the presence of the high concentrations of HCO3–, CO32–, F–, SO42–, Cl–, and NO3–. In addition, the uranyl tricarbonate in the loaded material could be easily eluted with a diluted hydrochloric acid. These advantages make P–C4 a new potential material for separating uranium from alkaline solution.