Electrochemical determination of diffusion coefficients of iron (II) ions in chloride melts at 700-750 °C

The diffusion coefficients of iron (II) ions depositing on solid tungsten electrodes in a molten chloride systems at about 700 °C have been determined by electrochemical techniques. The deposition process occurs under diffusion control for all the iron concentrations and temperatures studied. Conventional cyclic voltammetry and convolution cyclic voltammetry methods were used. Diffusion coefficients of iron (II) were calculated according to Randles-Sevcik and Berzins-Delahay equations for the conventional cyclic voltammetry and also by the limiting convoluted current for the convolution cyclic voltammetry. Convolution cyclic voltammetry is believed to be superior to conventional cyclic voltammetry for the quantitative evaluation of diffusion coefficients. The values of the diffusion coefficients lay in the range 1-40·10 ^-5 cm²/s for the temperature range of 700-750 °C. The Arrhenius temperature dependence of the diffusion coefficients is characterized by the value of E_a = 31.2 kj/mol.