U.S. Department of Energy

Pacific Northwest National Laboratory

Outcomes: Interfacial Diffusion and CRUD Formation at the Liquid-Liquid Interface of Solvent Extraction Processes

Principal Investigator: Amanda Casella

Completed: FY18

Outcomes: The project targeted a fundamental understanding of how crud (solids) forms at the liquid-liquid interface during solvent extraction processes. Initially, the project examined historical Hanford Site records, along with other open-literature published work to provide the framework and prioritization for experiments. The next step involved establishing and validating macro-scale testing along with implementation of complementary microfluidic studies--both aspects used in situ monitoring by Raman spectroscopy. In addition to experiments, computational approaches, including fluid dynamic modeling, were employed to gain further molecular insights regarding liquid-liquid interfacial processes. In the project's final year, systems involving mixtures of degradation products with the typical extraction components were studied to determine complexation and effects. Crud formation was studied within a microfluidic device to give a better understanding of fundamental rates of transfer, drivers, nucleation, and complexation at the liquid-liquid interface. The project provided stronger, more holistic fundamental understanding of crud formation.

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