Extraction of Nitric Acid and Uranium with DEHiBA under High Loading Conditions

Abstract

The mechanism by which high concentrations (1.5 M in n-dodecane) of N,N-di-2-ethylhexyl-isobutyramide (DEHiBA) extracts HNO3 and UO2(NO3)2 is under examination. Most prior studies have examined the extractant and the mechanism at a concentration of 1.0 M in n-dodecane; however, under the higher loading conditions that can be achieved by a higher concentration of extractant, this mechanism could change. Increased extraction of both nitric acid and uranium is observed with an increased concentration of DEHiBA. The mechanisms are examined by thermodynamic modeling of distribution ratios, 15N nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy coupled with principal 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 species of either UO2(NO3)2(DEHiBA) or UO2(NO3)2(DEHiBA)2(HNO3) also contributing to the extraction of uranium species is given.

Kinetics and Mechanism of Tetravalent Cerium Extraction by Di-2-Ethylhexyl Isobutyramide (DEHiBA)

“…5 The widely-cited explanation for the poor extraction of tetravalent species by DEHiBA is steric hindrance due to crowding of at least four nitrate anions and the branched isobutyl group preventing a strong interaction between the ligand and metal ion. 3,4,6 The favorable extraction of tetravalent actinides by the unbranched analogue di-2-ethylhexyl butyramide (DEHBA), which extracts approximately 80% of Pu(IV) at 1 M DEHBA, is used to further support this explanation. However, the Ce(IV) cation must also accommodate chargeneutralizing nitrates and the branched extractant, yet is notably more well-extracted than Pu(IV).…”

A self-optimised approach to synthesising DEHiBA for advanced nuclear reprocessing, exploiting the power of machine-learning

“…35–37 Recent publications from Hall et al highlight the continued interest and relevance of DEHiBA for the selective extraction of uranium, their research focussing on process intensification of uranium extraction, ensuring performance under various conditions. 38,39…”

Speciation and Organic Phase Structure in Nitric Acid Extraction with Trioctylamine

“…Anion-specific factors that can hinder or promote metal extraction, such as acid and water extractions, aggregation of extractants, and aqueous/organic speciation of the metal are thought to play a role in this phenomenon. − Such anion specificity in metal extraction is observed with different classes of extractants, including solvating-type and anion-exchange-type extractants. Acid and water extractions with solvating extractants − and their influence on metal extraction have been well studied. − Although amines show similar extraction trends and anion specificity, − they have received relatively less attention. Given that amines are hypothesized to extract metals by the anion-exchange mechanism, the effect of acid and water extraction on the extraction and stability of such anionic complexes is of interest.…”