Interfacial mass transfer of water for fluorobenzene/aqueous solution system in double emulsion

Abstract

Understanding the dissolution and diffusion process of water molecules across the oil/water interface is helpful to fabricate polymer shells with high surface quality. In this work, microscopic fluorobenzene/water, fluorobenzene/NaCl(aq) and fluorobenzene/1,3-butanediol(aq) systems are constructed by molecular simulation. The solubility of water in fluorobenzene and interfacial diffusion resistances is calculated by fitting the simulated dissolving curves to a one-dimensional surface evaporation continuum model. The equilibrium solubility, interfacial diffusion resistances and component diffusivities are calculated for the oil/water systems. The simulated water solubility and diffusivity in fluorobenzene at 320 K are 305 ppm and (8.38 ± 0.29) × 10−9 m2/s, respectively. The density distribution near the oil/water interface is statistical averaged and the solution microstructures are analyzed. Both the ions and alcohol molecules added in the aqueous phase can slow down the water dissolving process, by reducing the equilibrium solubility and interfacial mass transfer rate of water in fluorobenzene. Applying the properties provided by microscopic simulations to the macroscopic mass transfer model, the characteristic time t∞ (0.05–1.34 s) when the dissolved water mass reaches 95% of the equilibrium solubility is calculated for fluorobenzene membranes with a width range of 50–200 μm, which provides a time reference for double emulsions treatment process in polymer shell fabrication.