Comparative Studies on Third-Phase Formation in the Extraction of Thorium Nitrate by Tri- n -Butyl Phosphate and Tri- n -Amyl Phosphate in Straight Chain Alkane Diluents

This paper reports the results of the studies on third-phase formation during the extraction of thorium nitrate from solutions with near-zero free acidity by 1.1 M solutions of tri-n-butyl phosphate (TBP) and tri-n-amyl phosphate (TAP) in n-octane, n-decane, n-dodecane, n-tetradecane, and n-hexadecane. The concentration of Th(NO3)4 in the organic phase in biphasic regions and the distribution of Th(NO3)4 between the diluent-rich phase (DP) and the third phase (TP) in triphasic regions for the extraction from its solution with near-zero free acidity by the aforesaid solvents has been investigated as a function of equilibrium aqueous-phase thorium nitrate concentration at 303 K. Densities of organic phases in the biphasic and triphasic regions have been measured as a function of equilibrium aqueous-phase thorium nitrate concentration at 303 K. Also discussed are the variations of the ratios of the volume of the diluent-rich phase to that of the third phase as a function of the equilibrium aqueous-phase Th(NO3)4 concentration and chain length of the diluent in the extraction of Th(IV) from its solutions with near-zero free acidity by the above solvents at 303 K.