Lanthanide cation extraction by malonamide ligands: from liquid-liquid interfaces to microemulsions. A molecular...

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Liquid-liquid extraction is crucial for separating metal ions.
• Understanding interfacial behavior of ligands and complexes is key to optimizing extraction efficiency.
• Lanthanide and actinide extraction often involves complexation with organic ligands.

Purpose of the Study:

• To investigate the interfacial adsorption and structural behavior of malonamide ligands and their europium complexes.
• To elucidate the role of aqueous solvation and oil/water ratio on ligand and complex behavior at the interface.
• To understand the mechanisms underlying synergistic and solvation effects in assisted liquid-liquid extraction.

Main Methods:

• Molecular dynamics simulations were employed to model the system.
• The study simulated uncomplexed malonamide ligands (L) and their neutral Eu(NO3)3L2 or charged EuL4(3+) complexes.
• Interfacial behavior was analyzed under varying oil/water ratios and using different electrostatic models for the complexes.

Main Results:

• Malonamide ligands and their europium complexes exhibit surface activity, adsorbing at the water-chloroform interface.
• Aqueous solvation at the interface induces a trans to gauche rearrangement in carbonyl groups, preorganizing ligands for complexation.
• Increased oil/water ratio leads to the formation of water-in-oil micelles and micro-droplets, influencing adsorption and extraction.
• Neither neutral nor charged complexes were fully extracted into the organic phase.

Conclusions:

• The interfacial behavior and structural rearrangements of malonamide ligands and their europium complexes are critical for their adsorption and extraction.
• The findings provide insights into synergistic and solvation effects, aiding in the design of efficient liquid-liquid extraction systems for lanthanides and actinides.