Solvent extraction from molten salts—X: Extraction of perrhenate by alkylammonium salts

Abstract

The distribution of the perrhenate ion between eutectic mixtures of LiNO 3KNO 3 or NaSCN-KSCN and chloronaphthalene solutions of secondary or quarternary alkylammonium nitrates or thiocyanates has been studied in the 140–190°C temperature range. The distribution data have been interpreted in terms of anion exchange equilibria by taking into account the aggregation of the alkylammonium salt extractants, as found from independent vapor pressure lowering measurements under comparable experimental conditions. Equilibrium constants for the anion exchange reactions and the formation constants of homo- and hetero-oligomers have been calculated from distribution data. The formation constants of the homo-oligomers, whether obtained from distribution or vapor pressure lowering data, show a linear temperature dependence. Enthalpy values were calculated for the formation of these oligomers and for the anion-exchange reaction.