Polypropylene Modified with Amidoxime/Carboxyl Groups in Separating Uranium(VI) from Thorium(IV) in Aqueous Solutions

A majority of U/Th reprocessing studies are hampered in the production of large amounts of radioactive waste during extraction with organic complexes from highly acidic solutions. Polypropylene grafted with amidoxime/ carboxyl groups (PPAC), which exhibits selective binding toward U(VO, can help reduce organic waste. Batch studies on PPAC separating U(VI) from TOD/Th(IV) mixture in acidic to weak alkaline solution with complexing agent EDTA were carried out. The result suggested a much better affinity of PPAC to U(V1) over Th(IV). The pH effect study suggested the largest U/Th mass ratio at pH similar to 8. FTIR spectra at different pHs indicated most of the carboxyl and amidoxime functional groups were protonated at lower pH, while with increasing pH, the deprotonating degree increased correspondingly. X-ray diffraction analysis showed U(VI) and Th(IV) both enter the crystal lattice, resulting in smaller diffraction angle which was associated with U(VI) and Th(IV) adsorption capacity. This work revealed polymer or other material with amidoxime/carboxyl groups is a promising candidate for deployment as a uranium adsorbent in U/Th reprocessing.