The Effect of Alkyl Substitution on the Extraction Properties of BTPhen Ligands for the Partitioning of Trivalent Minor Actinides and Lanthanides in Spent Nuclear Fuels

Bis-triazinylphenanthroline ligands (btphens), which contain additional alkyl (n-butyl andsec-butyl) groups attached to the triazine rings, have been synthesized, and the effects of thisalkyl substitution on their extraction properties with ln(iii) and an(iii) cations in simulatednuclear waste solutions have been studied. the speciation of n-butyl-substituted ligand (c4-btphen) with some trivalent lanthanide nitrates was elucidated by ^1h-nmr spectroscopictitrations. these experiments have shown that the dominant species in solution were the 1:2complexes [ln(iii)(btphen)2], even at higher ln(iii) concentrations, and the relative stability of2:1 to 1:1 btphen-ln(iii) complexes varied with different lanthanides. as expected, sec-butylsubstituted ligand (sec-c4 btphen) showed higher solubility than c4-btphen in certain diluents. a greater separation factor (sfam/eu = ca. 210) was observed for sec-c4-btphen compared to c4-btphen (sfam/eu = ca. 125) in 1-octanol at 4 m hno3 solutions. the greater separation factor may be due to the higher solubility of the 2:1 complex for sec-c4-btphen at the interface than the 1:1 complex of c4-btphen.