The novel hydrophilic back-extraction agent TS-BTPhen (3,3',3'',3'''-[3-(1,10-phenanthroline-2,9- -diyl)-1,2,4-triazine-5,5,6,6-tetrayl]tetrabenzenesulfonic acid) was tested for its selectivity towards Am(III) over Cm(III) and Eu(III) with a TODGA (N,N,N',N'-tetraoctyldiglycolamide) based solvent. Batch experiments were carried out using TS-BTPhen dissolved in aqueous nitric acid solution with tracers of 152Eu, 241Am and 244Cm. A signifi cant increase of the separation factor for Cm over Am from SFCm/Am = 1.6 up to SFCm/Am = 3.3 was observed compared to the use of a TODGA-nitric acid system alone. Furthermore, stripping was possible at high nitric acid concentrations (0.6–0.7 mol/L) resulting in a low sensitivity to acidity changes. The infl uence of the TS-BTPhen concentration was analyzed. A slope of –2 was expected taking into account literature stoichiometries of the lipophilic analogue CyMe4BTPhen. However, a slope of –1 was found. Batch stripping kinetics showed fast kinetics for the trivalent actinides. As an alternative organic ligand the methylated TODGA derivate Me-TODGA (2-methyl-N,N,N',N'-tetraoctyldiglycolamide) was tested in combination with the hydrophilic TS-BTPhen. The Am(III) separation was achieved at even higher nitric acid concentrations compared to TODGA.
For the study of the coupled interfacial-mass transfer kinetics of, inter alia, TBP, TODGA, CyMe4-BTBP and CyMe4-BTPhen based solvent extraction processes, a new rotating diffusion cell (RDC) apparatus has been established at Lancaster University. RDC studies of Ce(IV)/TBP and Ce(III)/TODGA extraction systems have been undertaken in order to improve the understanding of the chemical and kinetic processes involved. In each case, an interesting dependency on local hydrodynamics at the solution phase boundary with results suggesting that the organic extractant molecules migrate into the aqueous phase in order to capture Ce.
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