Study of Diffusion of Co(II) and Co(II)-DEHPA Complex in a Microfluidic Device

Abstract

The use of microfluidic devices as analytical tools to probe the kinetics of interfacial reactions between heterogeneous phases such as those that occur in solvent extraction systems can provide important information on the interfacial processes that control these reactions. A number of studies have proposed the use of microfluidic devices for lab-on-a-chip processing. In either case, a detailed understanding of the hydrodynamic and diffusion behavior of the fluids in these devices is essential.In this study, the diffusion of Co(II) in an aqueous phase and the diffusion of the cobalt(II)-di-(2-ethylhexyl)-phosphate (Co(II)-DEHPA) complex in an organic phase were investigated in a double-Y-type microfluidic device. Diffusion experiments were carried out over a range of flow rates in the laminar flow region of the microfluidic device.A computational Fluid Dynamics (CFD) simulation of the flow field was carried out and the detailed velocity distribution in the channel was obtained; this distribution was used to predict the rate of diffusion of a solute. Furthermore, a simplified calculation mesh was developed for reducing the simulation time. The diffusion coefficients of Co(II) and the Co(II)-DEHPA complex were determined by the simulation to be 6.6×10−10 m2/s and 3.2×10−10 m2/s, respectively.