TWO-DIMENSIONAL MODEL OF STATIONARY TRANSFER OF BINARY ELECTROLYTE IN GALVANOSTATIC MODE

In electromembrane systems, the transfer of the binary electrolyte in the stationary case may be realized either in potentiostatic (PSR) (given the potential drop, ∆p (t) = const), or in galvanostatic (GSR) modes (given the average current density, Iav (t) = const). These modes are alternative to each other. At theoretical and experimental researches it is convenient to work in GSR. However, the system of Nernst-Planck-Poisson equations (NPP) is convenient for simulating transfer in the PSR, but inconvenient for simulating in the GSR, due to the lack of an equation for the current density. Using the method of mathematical transformations from the original system of equations of the NPP transfer model to the PSR, a system of equations modeling the transfer to the GSR is obtained. The numerical analysis is given using finite element methods. In work: a new equation for the current density is obtained from the NPP by transformations; the boundary conditions required to determine the current density are derived; an algorithm for calculating the current-voltage characteristic is developed. We performed a numerical analysis of the boundary value problem and showed that there is a complete correspondence between the current-voltage characteristics (CVC) calculated in the PSR and GSR at pre-limit densities and a slight difference at exorbitant current densities. This shows the adequacy of the proposed mathematical model of transfer in galvanostatic mode and the algorithm for calculating the CVC. The paper proposes a model of transfer in the GSR, numerical analysis of the boundary value problem and shows that there is a complete correspondence between the CVC calculated in the PSR and GSR at prelimit densities and a slight difference at exorbitant current densities. This confirms the adequacy of the proposed mathematical model of transfer in the galvanostatic mode and the algorithm for calculating the CVC. The proposed model of GSR transfer can serve as a mathematical tool for processing the results of experimental studies of GSR transfer.

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