A study of the nitrate and the chloride complexes of plutonium(VI) by solvent extraction technique using TTA as the chelating agent

Abstract

Solvent extraction of hexavalent plutonium from nitrate-perchlorate and from chloride-perchlorate mixtures into benzene containing thenoyl trifluoroacetone (TTA) has been studied with a view to investigating the formation of the nitrate and the chloride complexes of plutonium(VI). It is shown that only neutral chelates of PuO 2 2+ ions get extracted into the organic phase from perchlorate, nitrate or from chloride media. The equilibrium constants of PuO 2(NO 3) + and PuO 2Cl + have been calculated to be 0·93 and 1·05 respectively at an ionic strength of 4·1. In this work, using micro concentration of plutonium(VI), it was observed that the metal ions slowly got reduced to the more extractable plutonium(IV) state during the process of extraction and that the use of recommended holding oxidant permanganate or dichromate could not prevent this reduction completely. Further investigations showed that this reduction could be practically eliminated, if the solution phases were protected from light during the equilibration process. That plutonium(VI) ions can take part in photochemical reactions was qualitatively confirmed by irradiating a mixture of plutonium(VI) and oxalic acid in perchloric acid solution with ultra-violet rays and observing the reduction.