These are preliminary reports that have not been peer-reviewed. They should not be regarded as conclusive, guide clinical practice/health-related behavior, or be reported in news media as established information. For more information, please see our FAQs.
2 files

Hydrogen-Bond Driven Chemical Separations: Elucidating the Inter-facial Steps of Self-Assembly in Solvent Extraction

submitted on 03.03.2020, 16:14 and posted on 04.03.2020, 08:59 by Azhad U. Chowdhury, Lu Lin, Benjamin Doughty
Chemical separations, particularly liquid extractions, are pervasive in academic and industrial laboratories, yet a mechanistic understanding of the events governing their function are obscured by interfacial phenomena that are notoriously difficult to measure. In this work, we investigate the fundamental steps of ligand self-assembly as driven by changes in the interfacial H-bonding network using vibrational sum frequency generation. Our results show how the bulk pH modulates the interfacial structure of extractants at the buried oil/aqueous interface via the formation of unique H-bonding networks that order and bridge ligands to produce self-assembled aggregates. These extended H-bonded structures are key to the subsequent extraction of Co2+ from the aqueous phase in promoting micelle formation and subsequent ejection of said micelle into the oil phase. The combination of static and time resolved measurements reveals the mechanisms underlying complexities of liquid extractions at high [Co2+]:[DEHPA] ratios by showing an evolution of interfacially assembled structures that are readily tuned on a chemical basis by altering the compositions of the aqueous phase. The results of this work point to new mechanistic principles to design separations through the manipulation of surface charge, electrostatic screening, and the associated H-bonding networks that arise at the interface to facilitate organization and subsequent extraction


This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Chemical Sciences, Geosciences, and Biosciences Division.


Email Address of Submitting Author


Oak Ridge National Laboratory


United States

ORCID For Submitting Author


Declaration of Conflict of Interest

No conflict of Interest