Extraction chromatographic method for the separation of actinides and lanthanides using EDHBA grafted AXAD-16 polymer

Abstract

A new extraction chromatographic method has been developed by grafting chloromethylated polymer support with 4-ethoxy- N, N-dihexylbutanamide (EDHBA), for the selective extraction of U(VI), Th(IV), La(III) and Nd(III) from highly acidic matrices. The developed grafted polymer has been characterized using 13C-CPMAS NMR spectroscopy, FT-NIR spectroscopy and also by CHN elemental analysis. The water regaining capacity of the grafted polymer is studied by TGA measurements and the active participation of the amide moiety towards metal ion complexation has been confirmed by Far IR spectroscopy. For the quantitative extraction of metal ions to the resin phase, various physio-chemical parameters are optimized by both static and dynamic methods. The developed amide grafted polymeric matrix shows good distribution ratio values even at high acidities, with the maximum metal sorption capacity values being 0.36, 0.69, 0.32 and 0.42 mmol g −1 for U(VI), Th(IV), La(III) and Nd(III), respectively, at 6 M HNO 3 medium. The kinetics of metal ion phase equilibration is found to be moderately fast, with t 1/2 values of <6 min, for all the analytes of interest. The limits of analyte quantification (LOQ) using the developed method are in the range of 15–30 μg L −1. Moreover, the sequential separation of the sorbed actinides and lanthanides could be achieved by first eluting with 100 mL of distilled water (for actinides) followed by elution with 20 mL of 0.1 M EDTA (for lanthanides). The selectivity behavior and the practical applicability of the developed resin are tested using synthetic low level nuclear reprocessing mixtures and also with monazite sand. The analytical data are within 3.8% relative standard deviation, reflecting the reproducibility and reliability of the developed method.