The distribution and phase behavior of uranyl nitrate, extracted from acidic aqueous solutions by solvating organophosphorus extractants into nonpolar organic solvents, depend on their association in solution. That association is investigated with molecular dynamics simulations and electronic structure calculations. Uranyl nitrate complexes are found to form long-range isotropic pairs and short-range ordered dimeric assemblies. The stability long-range pair depends on extractant alkyl tail chain length while the short-range assembly is affected by changes to the structure of the extractant's polar head group. The energetics of association are further affected by the solvation environment and molecular structure of the organic solvent. At sufficiently high uranyl nitrate concentration, it is known experimentally that the organic phase partitions into solvate-rich and solvate-poor phases, in a deleterious phenomenon referred to as third phase formation. Simulations of such conditions show the short- and long-range pairs described above form extended clusters, revealing the “solvate percolation” mechanism of the phase transition. The role of extractant and solvent structure on the phase behavior of the high loading organic phase can therefore be connected to their impact on the pairwise association of the uranyl nitrate complexes.

Self-association and third phase formation of uranyl nitrate/TBP Complexes in PUREX-type solvent extraction systems

Macromolecular Chemistry: The Second Century

[Author Benefits](https://scimeetings.acs.org/?utm_source=pubs_content_marketing&utm_medium=website&utm_campaign=0320_MCF_NPI_Launch_Spring_Homepage&ref=pubs_content_marketing)

[How to use SciMeetings](https://storage.googleapis.com/dl.morressier.com/acs/SciMeetings-ACSSpring2020-HowToGuide_M3020-Final.pdf)

[Frequently Asked Questions](https://storage.googleapis.com/dl.morressier.com/acs/SciMtng_ACSNMSp2020_FAQ_M3120_Final.pdf)

ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.