Solubility Thermodynamics of CyMe $$_{4}$$ 4 -BTBP in Various Diluents Mixed with TBP

Abstract

The two organic ligands 6,6′-bis(5,5,8,8-tetramethyl-5,6,7,8-tetrahydrobenzo[1,2,4]triazin-3-yl)[2,2′]bipyridine (CyMe-BTBP) and tri-butyl phosphate (TBP) have previously been investigated in different diluents for use within recycling of used nuclear fuel through solvent extraction. The thermodynamic parameters, , , and , of the CyMe-BTBP solubility in three diluents (cyclohexanone, octanol and phenyl trifluoromethyl sulfone) mixed with TBP have been studied at 288, 298 and 308 K, both as pristine solutions and pre-equilibrated with 4 molL nitric acid. In addition, the amount of acid in the organic phase and density change after pre-equilibration have been measured. The solubility of CyMe-BTBP increases with an increased temperature in all systems, especially after acid pre-equilibration. This increased CyMe-BTBP solubility after pre-equilibration could be explained by acid dissolution into the solvent. Comparing the and calculated using with the same parameters derived from a linear fit indicates temperature independence of all three thermodynamic systems. The change in enthalpy is positive in all solutions.

Extraction Properties of 4-Tetra(hydroxyphenyl)BTPhen in Liquid-Liquid Extraction Systems with Cyclohexanone/Octanol or in a Solid-Phase Extraction System

“…Prospective diluents for the SANEX process must display high organic solubility of the ligand and its complexed species, high flashpoint, low water solubility (to avoid formation of emulsions), high stability in acidic media (4 M HNO3), resistance to radiolysis and be available in industrial quantities at low cost. 16,17 2 delete Both cyclohexanone and 1-octanol fulfil these requirements and have been proposed to be used in model SANEX processes. Tetra(4-hydroxyphenyl)-BTPhen 3 is more soluble in cyclohexanone (higher than 10 mM) than in octanol (5 mM), which raises the possibility for better extraction efficiency.…”