Characterization of reactive interfaces via coupled interfacial tension measurements and interphase mass transfer analysis

Abstract

Abstract To explore the kinetics of reactive interfaces we propose a scheme that couples the interphase mass transfer and interfacial phenomena studied with the profile analysis tensiometer (PAT). Heterogeneous reactions between two immiscible or partially miscible liquid phases were arranged by immersing a pendant droplet into a liquid matrix. This configuration enabled us to distinguish between periods of different phenomena such as diffusion, adsorption/desorption, reaction, unstable dissolution, partial miscibility, and equilibrium state by recording the changes of interfacial and geometric properties of the droplet as a function of time. For case studies, N,N-dimethylcyclohexylamine as a switchable hydrophilicity solvent and acetic acid were used as the reactive agents to provoke chemical reactions imposing desirable physical changes. For reactive and switchable systems, diffusion, reaction, and mass transfer periods could be detected reasonably. Also, the back-and-forth detachment/attachment of the non-reactive agent as an unstable dissolution was observed, which can lead to spontaneous emulsification. For the reactive and partially-miscible systems, four periods of partial miscibility, reaction and adsorption, desorption, and equilibrium could be detected. The material balance of a reactive droplet was also developed as the theoretical foundation to estimate the mass transfer coefficient of the external reactive component. The findings demonstrate that the application of dynamic tensiometry can be generalized into reactive interfaces and interphase mass transfers.