An Active Matter Pathway for Non-Equilibrium Liquid-Liquid Extractions

Abstract

We report on a Marangoni flow-driven pathway for non-equilibrium transport of metal ions across an oil-water interface. Under specific conditions, we show that the adsorption of a metallic species onto the extractant-decorated oil-water interface creates interfacial tension gradients that give rise to Marangoni flows. Strikingly, we observe that these flows are accompanied by removal of metal from the aqueous phase and that the extraction kinetics follow a non-diffusive behavior. The extraction rates are significantly higher - at least a threefold increase - when Marangoni flows are present. We show that the strength of the interfacial instability is coupled to the lowering of the interfacial tension- which is metal-dependent and therefore can lead to rate-mediated selective extractions. Overall, our study shows a fundamentally different paradigm for liquid-liquid extractions opening up a range of new directions of inquiry and future technologies.