**CURRENT-VOLTAGE CHARACTERISTIC OF NON-STATIONARY 1:1 SALT ION TRANSPORT IN THE SECTION OF DESALINATION
CHANNEL**

UDC 519.87+004.421

DOI:10.26102/2310-6018/2020.30.3.020

I.V. Shkorkina, N.O. Chubyr, V.A. Gudza, M.Kh. Urtenov

*The main goal of this work is to derive and analyze different formulas for calculating the current-voltage characteristic (CVC) of non-stationary transport of 1: 1 electrolyte in the cross-section of the desalting channel, including anion-exchange (AEM) and cation-exchange (CEM) membranes, and to establish fundamental regularities of changes in the CVC with time. Modeling is carried out based on the Nernst-Planck-Poisson equations. The transport of ions of strong electrolytes NaCl and KCl through a thin reaction layer of ion-exchange membranes in the section of the desalination channel is considered. For this purpose, a schematic electrical diagram of the current flow in the circuit, including the cross-section of the desalination channel, has been constructed. From the analysis of this circuit, it follows that the total current consists of a conduction current and a displacement current. The conduction current is determined by the flow of salt ions. The displacement current goes to the formation and development of the space charge region. Due to the change in the increase in the potential jump (potentiodynamic mode), the total current in the circuit when calculating the CVC changes over time, and its change can be considered slow. In this case, the displacement current practically does not pass through the cross-section of the desalination channel while the charge distribution density is slowly changing. In the case of a rapid change in the charge distribution density (breakdown phenomenon, as well as before and after breakdown), the displacement current takes on rather large values. The displacement current-voltage characteristic must be taken into account separately. Since the value of the CVC calculated in the study of the transport current is much higher than the value of the CVC at the displacement current, the effect of the electric “breakdown” on the transport current is hardly noticeable. Therefore, the “breakdown” effect must be investigated by the CVC of the displacement current. The proposed formula for calculating the CVC of the conduction current is stable with respect to rounding errors. The effect of nonstationarity is investigated at high growth rates of the potential jump.
*

**Keywords:** current-voltage characteristic, membrane systems, cross-section of the desalting channel, mathematical model, migration current, diffusion current.

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