How Acidity Rules Synergism and Antagonism in Liquid–Liquid Extraction by Lipophilic Extractants—Part I: Determination of Nanostructures and Free Energies of Transfer

Efficient formulations used in hydrometallurgy are often based on synergistic action of two oil-soluble extractants at an optimized mole fraction. In this series papers, we describe the N,N’-dimethyl-N,N’-dioctylhexylethoxymalonamide (DMDOHEMA)/di(2-ethylexyl) phosphoric acid (HDEHP) system, and how expression effect varies with acidity, using three common representations: distribution ratios, yields, free energies transfer. The experimental results detailed first part (Part I) so-called supramolecular approach, which considers reverse micelle-like aggregates formed by lipophilic extractant molecules. It shows that no specific aggregation state is observed maximum synergism antagonism. Besides, critical concentration characterizes micellization energy appears to follow some trends but cannot explain tunes antagonism mixed system. Based these results, Part II proposes a theoretical model ienaic approach interpret