Report

Electrochemical oxidation of 243Am(III) in nitric acid by a terpyridyl-derivatized electrode

Science  06 Nov 2015:
Vol. 350, Issue 6261, pp. 652-655
DOI: 10.1126/science.aac9217

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High fives and sixes for Americium ions

You've probably heard of uranium and plutonium. Americium (Am) is less widely discussed outside chemistry circles, but the separation of this heavier radioactive element from nuclear waste streams is a major goal of fuel reprocessing research. The trouble is that trivalent Am ions are hard to tease apart from similarly charged lanthanide ions. Dares et al. now show that terpyridyl ligands appended to an electrode can promote the oxidation of trivalent Am ions to the pentavalent and hexavalent states (see the Perspective by Soderquist). These more highly charged ions should be easier to isolate for the subsequent use of the Am in next-generation nuclear reactors.

Science, this issue p. 652; see also p. 635

Abstract

Selective oxidation of trivalent americium (Am) could facilitate its separation from lanthanides in nuclear waste streams. Here, we report the application of a high-surface-area, tin-doped indium oxide electrode surface-derivatized with a terpyridine ligand to the oxidation of Am(III) to Am(V) and Am(VI) in nitric acid. Potentials as low as 1.8 volts (V) versus the saturated calomel electrode were applied, 0.7 V lower than the 2.6 V potential for one-electron oxidation of Am(III) to Am(IV) in 1 molar acid. This simple electrochemical procedure provides a method to access the higher oxidation states of Am in noncomplexing media for the study of the associated coordination chemistry and, more important, for more efficient separation protocols.

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