THERMODYNAMIC MODELING OF THE EXTRACTION OF CADMIUM NITRATE BY THE TRUEX-NPH SOLVENT

The TRUEX solvent extraction process is being developed to remove low concentrations of transuranic (TRU) elements from high-level and TRU w astes currently stored at US Department of Energy sites. Cadmium is an important constituent of some of these wastes, especially at the Idah o Chemical Processing Plant. Cadmium distribution ratios were measured by using a radioactive Cd tracer under a variety of aqueous-phase com positions to elucidate the mechanism of cadmium extraction by TRUEX-NP H solvent at 25 degrees C. A model for predicting cadmium distribution ratios was developed as a function of the thermodynamic activities of water and nitrate ion. The Generic TRUEX Model (GTM) was used to calc ulate these activities. The GTMs calculation of activity coefficients is based on a Bromley method.