Role of Phase Modifiers in Controlling the Third-phase Formation During the Solvent Extraction of Trivalent Actinides

2019 ◽  
Vol 37 (7) ◽  
pp. 500-517 ◽  
Author(s):  
K. Rama Swami ◽  
K. A. Venkatesan ◽  
M. P. Antony
Keyword(s):  
Solvent Extraction ◽  
Phase Formation ◽  
The Third ◽  
Third Phase ◽  
Third Phase Formation ◽  
Trivalent Actinides

scholarly journals Reimagining Third Phase Formation as the Miscibility Gap of a Molecular Solution

2019 ◽  
Author(s):  
Michael Servis ◽  
David T. Wu ◽  
Jenife Shafer ◽  
Aurora Clark
Keyword(s):  
Solvent Extraction ◽  
Phase Formation ◽  
Organic Phase ◽  
Coexistence Curve ◽  
Phase Region ◽  
Dynamics Simulation ◽  
Miscibility Gap ◽  
Acid Extraction ◽  
Third Phase ◽  
Third Phase Formation

Liquid/liquid phase transitions are inherent to multicomponent solutions, which often contain a diversity of intermolecular interactions between their molecular constituents. In one such example, a phase transition is observed in liquid/liquid extraction where the nonpolar organic phase separates into two phases under sufficiently high metal and acid extraction by the amphiphilic extractant molecule. This deleterious phenomenon, known as third phase formation, complicates processing and limits efficiency. While empirically well documented, the molecular origin of this phenomenon is not understood. The prevailing conceptualization of the organic phase treats it as a microemulsion where extractant molecules form reverse micelles that contain the extracted aqueous solutes in their polar cores. Yet recent studies indicate that a microemulsion paradigm is insufficient to describe molecular aggregation in some solvent extraction systems, implying that an alternative description of aggregation, and explanation for third phase formation, is needed. In this study, we demonstrate that the formation of a third phase is consistent with crossing the liquid-liquid miscibility gap for a molecular solution rather than a Winsor II to Winsor III transition as presumed in the microemulsion paradigm. This insight is provided by using a graph theoretic methodology, generalizable to other complex multicomponent molecular solutions, to identify the onset of phase splitting. This approach uses connectivity obtained from molecular dynamics simulation to correlate the molecular-scale association of extractants and extracted solutes to the solution phase behavior using percolation theory. The method is applied to investigate a solvent extraction system relevant to ore purification and used nuclear fuel recycling: tri-n-butyl phosphate/uranyl nitrate/water/nitric acid/n-dodecane. In analogy to a molecular solution, immediately preceding the liquid-liquid coexistence curve from the single phase region, the metal-ligand complexes percolate. This demonstrates that describing this solution with microemulsion chemistry is neither applicable nor broadly required to explain third phase formation. Additionally, the method developed herein can predict third phase formation phase boundaries from simulation for this and potentially other solvent extraction systems.

Third phase formation behaviour of tris(2-methylbutyl) phosphate and tri-n-alkyl phosphates in the extraction of mineral acids and tetravalent metal ions

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Subramee Sarkar ◽  
A. Suresh ◽  
N. Sivaraman
Keyword(s):  
Phase Formation ◽  
Mineral Acid ◽  
Separation Processes ◽  
The Third ◽  
Third Phase ◽  
Metal Nitrates ◽  
Third Phase Formation ◽  
Mineral Acids ◽  
Nuclear Separation ◽  
Trialkyl Phosphates

Abstract The formation of third phase is a detrimental phenomenon witnessed in the nuclear separation processes during the extraction of certain metal salts by an organic solution, which comprises of a neutral extractant, tri-n-butyl phosphate dispersed in a non-polar diluent, n-dodecane (n-C12H26). In the present work, a comparative analysis on the third phase formation behaviour of three trialkyl phosphates, TBP, its linear and branched higher homologues tri-n-amyl phosphate and tris(2-methylbutyl) phosphate (T2MBP), respectively, have been provided which will be useful for the identification of an extractant with minimum third phase formation tendency. The organic phase splitting behaviour during the extraction of three mineral acids (HClO4, HCl and HNO3) and two tetravalent metal nitrates (Th(IV) and Zr(IV)) by trialkyl phosphates has been investigated to understand the influence of anionic and cationic components, respectively, in third phase formation of trialkyl phosphates. The effect of structure of the alkyl groups of trialkyl phosphate and chain length of diluents on third phase formation during Zr(IV) extraction from HNO3 media have also been studied. Overall, the third phase formation behaviour of T2MBP was found to be lower both for the extraction of mineral acid and Zr(IV), thereby indicating its potentiality for applications in various solvent extraction processes.

How Phase Modifiers Disrupt Third-phase Formation in Solvent Extraction Solutions

2021 ◽  
Vol 39 (2) ◽  
pp. 204-232
Author(s):  
Laurence Berthon ◽  
Amaury Paquet ◽  
Georges Saint-Louis ◽  
Philippe Guilbaud
Keyword(s):  
Solvent Extraction ◽  
Phase Formation ◽  
Third Phase ◽  
Third Phase Formation

Third phase formation in the extraction of Th(NO3)4 by Tri-sec-butyl phosphate: a comparison with Tri-n-butyl phosphate

2017 ◽  
Vol 105 (4) ◽  
Author(s):  
Aditi Chandrasekar ◽  
A. Suresh ◽  
N. Sivaraman
Keyword(s):  
Phase Formation ◽  
The Third ◽  
Third Phase ◽  
Third Phase Formation

AbstractEarlier studies carried out in our laboratory indicated that Tri-sec-butyl phosphate (TsBP) is a potential extractant for U/Th separation. Also, the third phase formation tendency of TsBP is lower compared to its isomers, Tri-

scholarly journals Solvent extraction of An(III) and Ln(III) using TODGA in aromatic diluents to suppress third phase formation

2020 ◽  
Vol 192 ◽  
pp. 105248
Author(s):  
Patrik Weßling ◽  
Udo Müllich ◽  
Elise Guerinoni ◽  
Andreas Geist ◽  
Petra J. Panak
Keyword(s):  
Solvent Extraction ◽  
Phase Formation ◽  
Third Phase ◽  
Third Phase Formation

scholarly journals Reimagining Third Phase Formation as the Miscibility Gap of a Molecular Solution

2019 ◽  
Author(s):  
Michael Servis ◽  
David T. Wu ◽  
Jenife Shafer ◽  
Aurora Clark
Keyword(s):  
Solvent Extraction ◽  
Phase Formation ◽  
Organic Phase ◽  
Coexistence Curve ◽  
Phase Region ◽  
Dynamics Simulation ◽  
Miscibility Gap ◽  
Acid Extraction ◽  
Third Phase ◽  
Third Phase Formation

Liquid/liquid phase transitions are inherent to multicomponent solutions, which often contain a diversity of intermolecular interactions between their molecular constituents. In one such example, a phase transition is observed in liquid/liquid extraction where the nonpolar organic phase separates into two phases under sufficiently high metal and acid extraction by the amphiphilic extractant molecule. This deleterious phenomenon, known as third phase formation, complicates processing and limits efficiency. While empirically well documented, the molecular origin of this phenomenon is not understood. The prevailing conceptualization of the organic phase treats it as a microemulsion where extractant molecules form reverse micelles that contain the extracted aqueous solutes in their polar cores. Yet recent studies indicate that a microemulsion paradigm is insufficient to describe molecular aggregation in some solvent extraction systems, implying that an alternative description of aggregation, and explanation for third phase formation, is needed. In this study, we demonstrate that the formation of a third phase is consistent with crossing the liquid-liquid miscibility gap for a molecular solution rather than a Winsor II to Winsor III transition as presumed in the microemulsion paradigm. This insight is provided by using a graph theoretic methodology, generalizable to other complex multicomponent molecular solutions, to identify the onset of phase splitting. This approach uses connectivity obtained from molecular dynamics simulation to correlate the molecular-scale association of extractants and extracted solutes to the solution phase behavior using percolation theory. The method is applied to investigate a solvent extraction system relevant to ore purification and used nuclear fuel recycling: tri-n-butyl phosphate/uranyl nitrate/water/nitric acid/n-dodecane. In analogy to a molecular solution, immediately preceding the liquid-liquid coexistence curve from the single phase region, the metal-ligand complexes percolate. This demonstrates that describing this solution with microemulsion chemistry is neither applicable nor broadly required to explain third phase formation. Additionally, the method developed herein can predict third phase formation phase boundaries from simulation for this and potentially other solvent extraction systems.

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