Effect of diluent on the extraction of europium(iii) and americium(iii) with N,N,N ',N '-tetraoctyl diglycolamide (TODGA)

Journal article, 2021

Solvent extraction of Eu3+ and Am(3+)via N,N,N ',N'-tetraoctyl diglycolamide (TODGA) dissolved in different molecular diluents was studied. The diluent types used in this work were primary and secondary alcohols, secondary ketones and alkanes. Effects of concentration of extracting agent, temperature, diluent type and its carbon chain length on the extractions were determined. Distribution ratios of Eu3+ and Am3+ showed high dependence on the diluent type as well as the carbon chain length within the same type of diluent. The highest distribution ratios for both Eu3+ and Am3+ as well as the separation factors of Eu3+ over Am3+ were observed in the alkane diluents. Unexpectedly high distribution ratios for Eu3+ and Am3+ were observed in polar diluents with 5 carbon atoms in the chain, clearly standing out against the general trends. It was found that Eu3+ and Am3+ extraction via TODGA is enthalpy driven in all the studied diluents and that extraction is more exothermic in alkane diluents. Analysis of the stoichiometry of the extracted complexes shows that the average ligand number of TODGA molecules in the extracted complex is lower for Am3+ compared to Eu3+ except for with alkane diluents.