High efficient separation of U(VI) and Th(IV) from rare earth elements in strong acidic solution by selective sorption on phenanthroline diamide functionalized graphene oxide

The extraction and separation of uranium (U(VI)) and thorium (Th(IV)) from rare earth elements (REEs) in acidic waste solutions is very important and still challenging. In this paper, a high-efficient sorbent was successfully prepared by functionalization of graphene oxide with phenanthroline diamide (GO-PDA), which exhibited excellent selectivity towards actinides over lanthanides. The sorption behaviors of GO-PDA towards U(VI) and Th(IV) under various conditions were evaluated by batch experiment. Fast sorption kinetics and high sorption capacities were realized for both U(VI) and Th(IV), which reached equilibrium in 60 min. The sorption isotherms of both U(VI) and Th(IV) coincided with Langmuir model, while the maximum sorption capacities of U(VI) (pH = 5.5) and Th(IV) (pH = 4.0) at 298 K were calculated to be 718 and 703 mg/g respectively, which were much higher than most of the previously reported graphene oxide (GO) based sorbents. GO-PDA also possessed significantly enhanced selectivity for U(VI) and Th(IV) over Eu(III), Nd(III) and Sm(III) compared to pristine GO at ultralow low pH (0−2), with separation factors larger than 23 at pH 0. Most importantly, GO-PDA was made into membrane with porous structure, which achieved fast and efficient separation of U(VI) and Th(IV) from Eu(III), Nd(III) and Sm(III) in aqueous solution. This work demonstrates that GO-PDA is a promising sorbent for efficient selective separation of U(VI) and Th(IV) from REEs in strong acidic waste solutions, which is of great value for nuclear waste management and nuclear fuel recycling.