Surfactin self-assembles into direct and reverse aggregates in equilibrium and performs selective metal cation extraction

Abstract

On tie-lines between water-rich and alkane-rich solutions, it is shown via scattering experiments that natural lipopeptide surfactin self-assembles into direct and reverse micelles in equilibrium. Elongated direct micelles in the aqueous phase are present together with small reverse globular aggregates in the organic phase. These latter are made from hydrated surfactant without any "water pool" in the organic phase. The resulting biphasic system is used for liquid-liquid extraction of model metal cations. It is efficient with iron but not with copper or neodymium. Competitive extractions show high selectivity towards iron.