NMR studies of uranyl benzenesulfonate solvation and phase diagram of uranyl benzenesulfonate-water-tributyl phosphate system

Abstract

Uranyl hydration and solvation numbers of uranyl benzenesulfonate (BSU) aqueous-organic solutions have been determined by means of dynamic NMR spectroscopy technique. Three aqua-complexes have been found to exist in aqueous-acetone solution: [UO2 (U6H5SO3)2·4H2O] and [UO2(C6H5SO3)2·(H2O)n] where n=1 or 2 and anions are bridging bidentate. Transition from [UO2 (C6H5SO3)2·4H2O] to the higher aqua complexes begins at P>40. There is a disolvate in the non-aqueous solution of BSU in tri-n-butyl phosphate (TBP). Composition of aqueous and organic phase of the BSU-water-TBP ternary system has been determined at room temperature, allowing to produce the phase diagram of the system. The binodale position is related to the anion amphiphilicity. The solvation number determined for BSU in the organic phases corresponds exactly to the low temperature data and allows to observe BSU dehydration and desolvation in the region of mutual dissolution of water and the organic phase, as well as TBP and the aqueous phase.