Phase equilibria in the liquid ternary system [Th(NO3)4(TBP)2]-[UO2(NO3)2(TBP)2]-Isooctane at different temperatures

Abstract

The phase diagrams of the ternary systems [Th(NO3)4(TBP)2]-[UO2(NO3)2(TBP)2]-isooctane in the temperature range 298.15–333.15 K were constructed. These diagrams contain the field of homogeneous solutions and the field of separation into two liquid phases (I, II). Phase I is enriched in [Th(NO3)4(TBP)2] and [UO2(NO3)2(TBP)2], and phase II is enriched in isooctane. With increasing temperature from 298.25 to 333.15 K, the mutual solubility of Th(NO3)4(TBP)2 and isooctane does not change noticeably, but the two-phase fields somewhat contract. In the two-phase systems [UO2(NO3)2(TBP)2] is preferentially distributed in phase I, although the binary system [UO2(NO3)2(TBP)2]-isooctane is single-phase over the entire temperature range examined. The preferential accumulation of [UO2(NO3)2(TBP)2] in phase I causes the redistribution of [Th(NO3)4(TBP)2] and isooctane into phases II and I, respectively. The compositions of the ternary systems in the critical points at different temperatures were determined. The electronic absorption spectra of uranyl nitrate solvate with TBP in the homogeneous and two-phase systems were recorded and analyzed.