Antimony Chloride Speciation Under Hydrothermal Conditions

Abstract

Radioisotopes of antimony are expected to be transported aschloro and chlorohydroxy complexes in supercritical water-cooled reactors at temperatures up to 600°C. These complexes have not been extensively studied at elevated temperatures, and accurate thermodynamic data are needed to model the transport of antimony. The objective of this project is to characterize these complexes through Gaussian calculations and Raman spectroscopy. Gaussian calculations predicted six stable complexes: SbCl₆^3- , SbCl₅^2-, SbCl₄^-, SbCl₃⁰, SbCl₂OH⁰ and SbCl(OH)₂⁰. The SbCl₆^3- and SbCl₄^- species in solution have been characterized with Raman spectroscopy using the bands predicted by Gaussian. The spectra thus far indicated that in concentrated Cl^- solutions, the equilibrium shifts to the lower charged complexes up to 250°C, which is inferred from the increasing Raman shift of the symmetric bands within the spectra. Experiments are continuing to identify and quantify the other complexes to determine the equilibrium constants.