Essence into the kinetic enhanced extraction induced by Marangoni convection on the surface of freely rising oil droplets

[Display omitted] •Marangoni instability depends on interfacial nonhomogeneous chemical reaction.•Marangoni convection is more likely to occur on the surface of the smaller droplets.•The occurrence depends on chemical reaction rate slightly greater than renewal rate.•Stronger interaction of RE3+ with P204 indicated an obvious interfacial fluctuation.•A novel perspective to understand microscopic nature of kinetic enhanced extraction. The enhanced separation of rare earth ions depending on different kinetic extraction behaviors can be achieved by extraction on the surface of rising droplets, where exists the nonhomogeneous chemical reaction. Marangoni instability might occur dependent on nonhomogeneous chemical reaction, which is conducive to the enhancement of interfacial mass transfer. To explore the influence from a nonhomogeneous chemical reaction on the generation of Marangoni instability, influences from the flow rate of oil droplets and the oil droplet size on interfacial extraction behaviors were performed, the interfacial tension was evaluated, and MD simulations combined DFT calculations were adopted. It was revealed that the higher interface renewal rate of the large oil droplet was favorable for the interfacial chemical reaction. Whether the interfacial extraction rate is greater than the interface renewal rate decided the occurrence of Marangoni convection. The current research highlights a novel viewpoint towards understanding microscopic nature of kinetic enhanced extraction.