The behaviour of tributyl phosphate in an organic diluent

Laura Leay, Kate Tucker, Annalaura Del Regno, Sven L M Schroeder, Sven Schroeder, Clint A. Sharrad, Andrew J. Masters

    Research output: Contribution to journalArticlepeer-review

    Abstract

    Tributyl phosphate (TBP) is used as a complexing agent in the Plutonium Uranium Extraction (PUREX) liquid-liquid phase extraction process for recovering uranium and plutonium from spent nuclear reactor fuel. Here, we address the molecular and microstructure of the organic phases involved in the extraction process, using molecular dynamics to show that when TBP is mixed with a paraffinic diluent, the TBP self-assembles into a bi-continuous phase. The underlying self-association of TBP is driven by intermolecular interaction between its polar groups, resulting in butyl moieties radiating out into the organic solvent. Simulation predicts a TBP diffusion constant that is anomalously low compared to what might normally be expected for its size; experimental nuclear magnetic resonance (NMR) studies also indicate an extremely low diffusion constant, consistent with a molecular aggregation model. Simulation of TBP at an oil/water interface shows the formation of a bilayer system at low TBP concentrations. At higher concentrations, a bulk bi-continuous structure is observed linking to this surface bilayer. We suggest that this structure may be intimately connected with the surprisingly rapid kinetics of the interfacial mass transport of uranium and plutonium from the aqueous to the organic phase in the PUREX process. © 2014 Taylor & Francis.
    Original languageEnglish
    Pages (from-to)2203-2214
    Number of pages11
    JournalMOLECULAR PHYSICS
    Volume112
    Issue number17
    DOIs
    Publication statusPublished - 2 Sep 2014

    Keywords

    • bi-continuous phase
    • micro-emulsion
    • molecular dynamics
    • PUREX
    • self-assembly
    • TBP
    • tributyl phosphate

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