Highly Efficient Extraction Chromatography Resins Containing Dendrimers with DGA Groups in Ionic Liquid for Actinide Uptake

Diglycolamide (DGA)-functionalized poly(propyleneimine) diaminobutane dendrimers of the first (DGA-Den-I) or second (DGA-Den-II) generation and a room temperature ionic liquid (RTIL), viz., 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide, based extraction chromatography resins were prepared for minor actinide separations from high level radioactive waste. The weight distribution coefficients (K_d) of actinides on the two resins gave excellent and selective sorption of Am(III) and Pu(IV) over hexavalent uranyl ions, Sr(II) and Cs(I), over a wide range of acidity (0.01-6 M HNO₃). The sorbed Am(III) and Pu(IV) could be efficiently desorbed with a buffered complexing solution of 1 M guanidine carbonate + 0.05 M EDTA. The sorption of metal ions on both the resins followed pseudo-second order rate kinetics and proceeded via a chemisorption phenomenon with a sorption energy of 13.4 ± 0.2 kJ/mol. The resin capacities were estimated to be 4.64 ± 0.18 and 4.19 ± 0.21 mg of Eu per g of DGA-Den-I and DGA-Den-II resins, respectively. The column loading of Eu(III) was about 85% of the theoretical value with a narrow elution profile using a buffered complexing solution. The resin affinity toward U(VI), Sr(II), and Cs(I) cations over Am(III) and Pu(IV) was poor, indicating the possible use of the resins for selective separation of Am(III) and Pu(IV) from other metal ions over a wide range of feed acidity.