Purifying the f-elements is necessary for nuclear waste remediation, diagnostic or therapeuticmedical applications, and to enable fundamental chemistry with these relatively rare
elements. These separations are challenging because the lanthanides (Ln) and minor actinides
(An) often share an oxidation state (M(III)) and have similar ionic radii, precluding common
techniques like size exclusion chromatography. This dissertation considers the separations
and fundamental chemistry of specific f-elements in two decay chains - 227Ac and 254Es - as
well as lower-Z analogs Gd, Ce and Cs.
Ac is interesting to study because it has the largest ionic radius of all the f-elements
and is more difficult to chelate, but an effective chelator in biological systems is necessary to
facilitate 225Ac targeted alpha therapies. A series of solution thermodynamic experiments
using liquid/liquid extraction (LLE) probes the efficacy of eleven linear molecules as Ac
chelators and compares those results to Gd as an analogous lanthanide. In general, the
ligands chelates Gd more strongly than Ac, although the two phosphonic acids studied
effectively retain Ac in the aqueous phase at lower concentrations than necessary for Gd
retention. The octadentate hydroxypyridinone-based ligand 3,4,3-LI(1,2-HOPO) (343HOPO),
which has been widely used for separations and fundamental investigations of the actinides,
demonstrates similar behavior to diethylenetriamine pentaacetate (DTPA), a commonly used
ligand in nuclear waste LLE systems. 343HOPO outperforms three catecholamide-containing
ligands with the same backbone, and also outperforms the other carboxylic acids evaluated.
In addition to this Ac solution chemistry, fundamental properties of the last two Group 1
metals, Cs and Fr, were explored using 137Cs and 223Fr via a different LLE system. Three
crown ethers with increasing cavity sizes were compared for each element, and the results
indicate a surprisingly similar size match between the two metals. These experiments present
the first set of solution thermodynamic measurements conducted with a pure stream of Fr,
and the first with 223Fr (t1/2 = 22 min); previous experiments have used 225Ac as an in situ
generator of the short-lived 221Fr (t1/2 = 4.7 min).
To produce this pure stream, a column-based scheme for rapid separation of 227Ac from
its daughters 227Th, 223Fr, and 223Ra was developed, which can be used to obtain radio- and
chemically-pure 223Fr as frequently as every 3 hours for at least 14 days. In addition, the
procedure provides clean streams of the other 227Ac daughters, 227Th and 223Ra, both of
which could be used as other targeted alpha therapy agents. A final set of column separation
experiments consider schemes to separate Es/Bk/Cf, including a novel ionic exchange resin-based
separation of Bk from Cf using 343HOPO's unique oxidizing power to change the
overall charge of the Bk(343HOPO) complex.
Furthering characterization of f-element-343HOPO complexes, 254Es(343HOPO) luminescence
was measured, corroborating previous measurements of a blue shift upon Es complexation
in contrast with the other actinides, which are red-shifted upon complexation. X-ray
absorption spectroscopy (XAS) measurements of 254Es(343HOPO) and Ce(IV/III)(343HOPO)
are also presented. The 254Es(343HOPO) XAS measurements include the first measurement
of the elemental white line (closely corresponding to theory) and unexpectedly short M-O
bond lengths, indicating a potential break in the An series. The Ce(343HOPO) measurements
show beam-induced reduction of the complexed metal, demonstrating 343HOPO's
remarkable oxidizing power, and providing a potential explanation for the challenges experienced
in measuring Bk(IV)(343HOPO) via XAS despite solutions-based measurements that
clearly demonstrate that oxidation state. Some initial forays into other ligands that mimic
343HOPO's oxidation of Ce are also presented, again with an eye toward biologically-relevant
ligands and/or systems where Ce can be replaced with Bk.
A final chapter considers the history of nuclear isotope production, evaluating the extent
to which super heavy element researchers and research facilities can be considered science
diplomacy, rather than 'mere' international science. While the common taxonomies of science
diplomacy emphasize scientists' actions instead of state participation, a state-centered analysis
that evaluates the dichotomy of competition and cooperation in the field concludes that some
nations pursue the discovery of new elements for the science while others have international
agendas.