Impact of Water Extraction on Malonamide Aggregation: A Molecular Dynamics and Graph Theoretic Approach

Area of Science:

• Chemical Engineering
• Materials Science
• Physical Chemistry

Background:

• Solution structure critically impacts liquid-liquid extraction efficiency.
• Characterizing molecular aggregation in organic phases is challenging.
• Amphiphilic extractants like malonamides are key in actinide and lanthanide separations.

Purpose of the Study:

• To investigate water uptake in organic phases for malonamide-based liquid-liquid extraction.
• To characterize the structure and aggregation behavior of water-malonamide systems.
• To understand the impact of water on the self-association of malonamides.

Main Methods:

• Atomistic molecular dynamics simulations were employed.
• A graph theoretic approach defined hydrogen-bonded aggregates.
• Small-angle X-ray scattering was used for comparison.
• Analysis of malonamide self-association topology was performed.

Main Results:

• Water uptake induces reorganization of amphiphilic malonamide molecules.
• A characteristic aggregate size based on water number was identified.
• This suggests inherent size selectivity in water-in-oil aggregates.
• No characteristic aggregate size was found based on malonamide number.
• Water alters the local and nonlocal topology of the malonamide network.

Conclusions:

• Water-in-oil aggregates in malonamide systems exhibit size selectivity based on water content.
• Molecular dynamics and graph theory provide insights into complex solution structures.
• Understanding these structures is crucial for optimizing separation processes.