Amide grafted amberlite XAD-16 polymer for the selective and sequential separation of U(VI) and Th(IV) from acidic waste effluents

The newly developed amide grafted polymer, p-amino-N,N-dihexylacetamide (ADHA) anchored on Amberlite XAD-16 (polystyrene-divinylbenzene co-polymer) solid support, shows greater selectivity in extracting U(VI) over Th(IV) and lanthanides from highly acidic matrices. It serves as an efficient solid phase extractant to perform an extraction chromatographic separation of U/Th. The grafting process is monitored by C-13-CPMAS NMR spectroscopy, FT-NIR spectroscopy, and CHN elemental analysis. U(VI) has a separation factor value of 8.03 over Th(IV) at 3 M HNO3 medium, which is governed by the steric hindrance imposed by the anchored amide moiety. Moreover, the resin shows non-extractive behavior for all transition metal ions along with various diverse ions that are commonly present in nuclear spent fuel solutions. It possesses a superior metal sorption capacity value of 0.692 mmol/g for U(VI) at 4 M HNO3 medium and also exhibits faster phase exchange kinetics. The practical utility in selectively separating U(VI) from Th(IV) and rare earth ions has been tested using a synthetic low-level nuclear reprocessing mixture. Analytical data obtained from both batch and column studies are within 3.8% relative standard deviation (rsd) based on triplicate measurements, thereby reflecting the reproducibility and reliability of the developed method.