Investigation of the Phase Splitting Behaviour of U(VI) and Th(IV) loaded Trialkyl Phosphate Solvents in the Absence of Aqueous Phase

Abstract

Tri‐n‐butyl phosphate (TBP), a universally recognized solvent, has got lesser organic phase splitting or third phase formation tendency during the extraction of U(VI) as compared to tetravalent metal ions. Thus, the lighter members of trialkyl phosphates (TalP) (i. e.) tri‐n‐propyl phosphate (TPP) and triethyl phosphate (TEP) having higher third phase formation tendency would provide an opportunity to comprehend the aggregation of U(VI) loaded TalP solvents. As the above lighter TalPs exhibit higher aqueous solubility, the conventional measurement of third phase limit or Limiting Organic Concentration (LOC) by mixing organic and aqueous phases cannot be employed for the investigation of U(VI) third phase in TalPs. This has led to the development of a novel method to examine U(VI) third phase in aqueous soluble TalP solvent systems without aqueous feed solution. After validation, the newly developed method has then been utilized to determine the LOC for 1.1 M TPP in n‐alkane. The variation of extractant structure, diluent chain length, nature of metal ion and temperature on the third phase of 1.1 M TalP systems has been evaluated along with their molecular level understanding using Dynamic Light Scattering.

Critical fluctuations in liquid–liquid extraction organic phases controlled by extractant and diluent molecular structure

“…45 The resulting three-phase system is incompatible with processing equipment, resulting in a limit to the per-contact loading capacity of the organic phase. While organic phase structure has long been linked to its phase behavior, 20,39,43,[46][47][48][49][50][51][52][53][54][55][56][57][58] we recently proposed that organic phase structure over a wide range of binary extractant/diluent mixtures is consistent with critical fluctuations originating from the critical point associated with the third phase formation phase transition. 59,60 That is, organic phase structuring is consistent with what would be expected from the concentration fluctuations induced by the critical point associated with the liquid-liquid phase transition.…”

Critical Fluctuations in Liquid-Liquid Extraction Organic Phases Controlled by Extractant and Diluent Molecular Structure

“…While organic phase structure has long been linked to its phase behavior, 20,39,43,[46][47][48][49][50][51][52][53][54][55][56][57][58] we recently proposed that organic phase structure over a wide range of binary extractant/diluent mixtures is consistent with critical fluctuations originating from the critical point associated with the third phase formation phase transition. 59,60 This could explain certain limitations to common microemulsion descriptions of LLE systems, such as the presence of structure in the organic phase even in the absence of extracted polar solutes needed to induce the formation of water-in-oil aggregates.…”

Insights into water extraction and aggregation mechanisms of malonamide-alkane mixtures

“…[5][6][7][8] Thus, understanding the fundamental mechanisms and influential factors of aggregation and water extraction is vital to designing cleaner and more efficient solvent extraction processes. Extractant aggregation in the organic phase has also been connected to third phase formation, [9][10][11][12][13][14][15][16][17][18] a deleterious phenomenon where, upon sufficient extraction of polar solutes, the organic phase splits into an extractant-rich lower phase and a diluent-rich upper phase. [19][20][21] This liquid-liquid phase transition often limits the loading capacity of the polar solute of interest, such as the targeted metal ion.…”