A Telescoping View of Solute Architectures in a Complex Fluid System

Area of Science:

• Solution chemistry
• Soft matter physics
• Materials science

Background:

• Complex fluids with multiscale aggregates are vital for energy-relevant separation and catalytic processes.
• Solute mass transfer across liquid-liquid interfaces is a core function, often influenced by micellar structures in microemulsions.
• Understanding these structures is key to optimizing phase transfer chemistry and predicting phase splitting.

Purpose of the Study:

• To elucidate the microscopic structures and mesoscopic architectures of metal-, water-, and acid-loaded organic phases.
• To investigate the aggregation behavior of metal ions during phase transfer.
• To provide a structural perspective on phase splitting phenomena in complex fluids.

Main Methods:

• Combined X-ray and neutron experimentation.
• Density functional theory (DFT) and molecular dynamics (MD) simulations.
• Analysis of a quinary system (zirconium nitrate-nitric acid-water-tri-n-butyl phosphate-n-octane).

Main Results:

• Metal ion transfer involves the formation of mononuclear clusters (metal-ligand coordination) and their subsequent aggregation into multinuclear clusters and supramolecular superclusters.
• A hierarchical structure of aggregation was observed, from small clusters to large superclusters.
• Experimental and simulation data provide a structural understanding of aggregation, complementing existing energetic models.

Conclusions:

• The aggregation hierarchy observed is fundamental to understanding solution phase transitions and the behavior of engineered fluids in mass transfer.
• This work offers insights into demixing in separation processes and synthesis in catalysis.
• The findings contribute to a more general phase-space model of soft matter self-assembly and particle growth.