PNNL

Abstract

The extractant, N,N-di-2-ethylhexyl-isobutyramide (DEHiBA), is under examination for its ability to selectively extract uranium. The present study focuses on improving uranium extraction efficiency by increasing the DEHiBA concentration from 1.0 M to 1.5 M. Increased extraction of both nitric acid and uranium is observed with the increased concentration of extractant. The mechanisms by which extraction occurs is examined by thermodynamic modeling of distribution ratios and FTIR spectroscopy coupled with Principle Component Analysis (PCA). Speciation diagrams produced through thermodynamic modeling have been qualitatively reproduced through PCA of the FTIR spectra. The predominant extracted species of HNO3(DEHiBA), HNO3(DEHiBA)2, and UO2(NO3)2(DEHiBA)2 are in good agreement with prior literature reports for 1.0 M DEHiBA systems. Evidence for an additional organic phase uranium species of UO2(NO3)2(DEHiBA) is given by a combination of thermodynamic modeling and 15N NMR spectroscopy.