TY - JOUR
T1 - Separation of the Minor Actinides Americium(III) and Curium(III) by Hydrophobic and Hydrophilic BTPhen ligands
T2 - Exploiting Differences in their Rates of Extraction and Effective Separations at Equilibrium
AU - Lewis, Frank W.
AU - Harwood, Laurence M.
AU - Hudson, Michael J.
AU - Afsar, Ashfaq
AU - Laventine, Dominic M.
AU - Šťastná, Kamila
AU - John, Jan
AU - Distler, Petr
PY - 2018
Y1 - 2018
N2 - The complexation and extraction of the adjacent minor actinides Am(III) and Cm(III) by both hydrophobic and hydrophilic pre-organized 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenanthroline (BTPhen) ligands has been studied in detail. It has been shown that Am(III) is extracted more rapidly than Cm(III) by the hydrophobic CyMe4-BTPhen ligand into different organic diluents under non-equilibrium extraction conditions, leading to separation factors for Am over Cm (SFAm/Cm) as high as 7.9. Furthermore, the selectivity for Am(III) over Cm(III) can be tuned through careful choice of the extraction conditions (organic diluent, contact time, mixing speed, ligand concentration). This ‘kinetic’ effect is attributed to the higher presumed kinetic lability of the Am(III) aqua complex towards ligand substitution. A dependence of the Am(III)/Cm(III) selectivity on the structure of the alkyl groups attached to the triazine rings is also observed, and BTPhens bearing linear alkyl groups are less able to discriminate between Am(III) and Cm(III) than CyMe4-BTPhen. Under equilibrium extraction conditions, hydrophilic tetrasulfonated BTPhen ligands complex selectively Am(III) over Cm(III) and prevent the extraction of Am(III) from nitric acid by the hydrophobic O-donor ligand N,N,N’,N’-tetraoctyldiglycolamide (TODGA), giving separation factors for Cm(III) over Am(III) (SFCm/Am) of up to 4.6. These results further underline the utility of the BTPhen ligands for the challenging separation of the chemically similar minor actinides Am(III) and Cm(III).
AB - The complexation and extraction of the adjacent minor actinides Am(III) and Cm(III) by both hydrophobic and hydrophilic pre-organized 2,9-bis(1,2,4-triazin-3-yl)-1,10-phenanthroline (BTPhen) ligands has been studied in detail. It has been shown that Am(III) is extracted more rapidly than Cm(III) by the hydrophobic CyMe4-BTPhen ligand into different organic diluents under non-equilibrium extraction conditions, leading to separation factors for Am over Cm (SFAm/Cm) as high as 7.9. Furthermore, the selectivity for Am(III) over Cm(III) can be tuned through careful choice of the extraction conditions (organic diluent, contact time, mixing speed, ligand concentration). This ‘kinetic’ effect is attributed to the higher presumed kinetic lability of the Am(III) aqua complex towards ligand substitution. A dependence of the Am(III)/Cm(III) selectivity on the structure of the alkyl groups attached to the triazine rings is also observed, and BTPhens bearing linear alkyl groups are less able to discriminate between Am(III) and Cm(III) than CyMe4-BTPhen. Under equilibrium extraction conditions, hydrophilic tetrasulfonated BTPhen ligands complex selectively Am(III) over Cm(III) and prevent the extraction of Am(III) from nitric acid by the hydrophobic O-donor ligand N,N,N’,N’-tetraoctyldiglycolamide (TODGA), giving separation factors for Cm(III) over Am(III) (SFCm/Am) of up to 4.6. These results further underline the utility of the BTPhen ligands for the challenging separation of the chemically similar minor actinides Am(III) and Cm(III).
KW - Americium
KW - 1,2,4-triazine
KW - curium
KW - separation
KW - kinetic effect
KW - BTPhen ligand
U2 - 10.1080/07366299.2018.1429358
DO - 10.1080/07366299.2018.1429358
M3 - Article
SN - 0736-6299
VL - 36
SP - 115
EP - 135
JO - Solvent Extraction and Ion Exchange
JF - Solvent Extraction and Ion Exchange
IS - 2
ER -