Extraction properties of 6,6′-bis-(5,6-dipentyl-[1,2,4]triazin-3-yl)-[2,2′]bipyridinyl (C5-BTBP)

The extraction of americium(III) and europium(III) into a variety of organic diluents by 6,6'-bis-(5,6,-dipentyl-[1,2,4]triazin-3-yl)-[2,2']bipyridinyl (C5-BTBP) has been investigated. In addition to determining the stoichiometry for the extraction, the dependence of extraction on contact time and temperature was also studied. The resistance of the ligand to gamma irradiation and the possibility to recycle the organic phase after stripping were tested to determine how the molecule would perform in a radiochemical process. Different organic diluents gave different extraction results, ranging from no extraction to distribution ratios of over 1000 for americium(III). In 1,1,2,2-tetrachloroethane, the extraction and separation of americium from europium and the extraction kinetics were good; a separation factor above 60 was obtained at equilibrium, similar to 5 min contact time. The extraction capabilities are adequate for C5-BTBP to be used in a process for separating trivalent actinides from lanthanides. However, C5-BTBP is susceptible to radiolysis (americium extraction decreases similar to 80% after a dose of 17 kGy) and may not be the best choice in the processing of spent nuclear fuel. Nonetheless it is a useful starting point for further development of this type of molecule. It could also prove useful for analytical scale separations for which radiolytic instability is less important.