A novel measurement method for measuring the concentration-dependent mutual diffusion coefficients based on finite volume method

This paper presents a novel measurement method based on the finite volume method (FVM), which can be used for measuring the concentration-dependent mutual diffusion coefficient D(C) in binary solution. The measurement principle of D was derived by integrating the Fick's second law in the control volume and establishing discretization equation. By simulating the diffusion process of binary solution, discussed the feasibility of this method. This new method can be used by an experimental system that can monitor changes in concentration distribution, such as optical interferometry. A set of 20 binary mixtures was tested to verify the method. The experimental results showed good agreement with and the literature, which verifies the accuracy of the method. The relative expanded combined uncertainty for the proposed method is estimated to 2.2 %. In addition, D(C) of LiTSFI aqueous solution was measured by the new method based on the digital holographic interferometry system at 288.15 K, 298.15 K and 308.15 K over the mass fraction range of 0 ∼ 0.447 (0 ∼ 2 mol/L). The temperature and concentration influences of D were discussed and a semi-empirical correlation was built.