This paper caught my attention immediately as I was scrolling through the rss feed. It’s not that I’m generally interested in chemistry of actinide metals. But for a chemist it’s always refreshing to be reminded of elements from the subscript of the periodic table.
I certainly didn’t know too much about americium beyond its use in smoke detectors. As it turns out from the introduction, Am-241 pollutes nuclear wastes (well, that sounds weird) by generating too much heat from its decay. In principle, the decay heat is not always the bad thing, so isolation of Am from lantanides and other radioactive fellows seems to be a worthwhile business.
But as one can imagine, it’s not that easy if the previous reagents of choice are phosphotungstates and bismutates. The scope of the problem can be appreciated from the following trial experiment:
No Am(III) oxidation was observed using underivatized electrodes at potentials between 1.8 and 2.7 V versus SCE. Noticeable electrode decomposition was evident at potentials above 2 V for electrolysis periods as short as 1 hour.
So the team of brave chemists from North Carolina and Idaho used the power of nanotechnology. Surface-modified electrodes, covalently coated with tripyridine chelating ligand were used for taming stubborn Am(III). So the reduced form bound to the surface, got oxidized at relatively low potential, and then released as the affinity of higher oxidation states to the immobilized ligand was not as high. That’s pretty neat, and even despite noxious radiolysis-born reducing leftowers of water floating around, the team managed to reach 93% of Am(V) and Am(VI) in the reaction mixture.
Too bad, a test isolation of americium from a complex mix is not reported, so it’s hard for one from outside the field to estimate selectivity of the developed electrode. Hence, the whole story remains somewhat incomplete.