The world’s oceans contain a potentially limitless source – 4.5 billion tons – of untapped uranium for nuclear power production. However, efforts to extract this uranium are complicated by the fact that in slightly alkaline seawater, uranium exists as the very stable Ca2[UO2(CO3)3] complex at an extremely dilute concentration (3.3 µg L-1) along with a variety of other metal cations. Therefore, a suitable extractant must be able to outcompete carbonate and selectively extract the dilute uranium from seawater. Currently, the most promising extractants are poly(acrylamidoxime) sorbents that contain the amidoxime (-C-(NH2)NOH) moiety.1 In particular, glutarimidedioxime, a cyclic imidedioxime that can be formed during sorbent synthesis, forms very strong complexes with uranium under seawater conditions.2 Although glutarimidedioxime-based sorbents are selective for uranium over many other seawater cations, recent marine tests have indicated that there is higher sorption of vanadium than uranium and that, once sorbed, vanadium is difficult to desorb. In an effort to explain the high sorption of vanadium and to expand our thermodynamic model of glutarimidedioxime complexation with seawater cations, we have investigated the thermodynamics of vanadium complexation with glutarimidedioxime. Preliminary experiments indicate that vanadium-glutarimidedioxime complexes form over a wide pH range and are significantly stronger than the analogous complexes formed with U(VI). They are the strongest glutarimidedioxime complexes observed thus far, with the order of thermodynamic stability being V(V) &gt; Fe(III) &gt; U(VI) ~ Cu(II) &gt; Pb(II) &gt; Ni(II) &gt; Ca(II) ~ Mg(II). At low pH, evidence of reduction of VO2+ to VO2+ by glutarimidedioxime was observed. References 1. Kim, J.; Tsouris, C.; Mayes, R. T.; Oyola, Y.; Saito, T.; Janke, C. J.; Dai, S.; Schneider, E.; and Sachde, D. Sep. Sci. Technol. 2013, 48, 367-387. 2. Tian, G.; Teat, S. J.; Zhang, Z.; and Rao, L. Dalton Trans. 2012, 41, 11579-11586.

Complexation of glutarimidedioxime with V(V), a major competing ion for the extraction of U(VI) from seawater

249th National Meeting (2015)

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