The Role of Chlorine Dioxide in the Electroreduction of Chlorates at Low pH.

The specific features of the electroreduction of chlorates in strongly acidic aqueous solutions are studied by carrying out the electrolysis of 12.5 mM solution of sodium chlorate in 8 M sulfuric acid under potentiostatic conditions at the limiting cathodic current. The periodically collected optical spectrum of solution reveals the main contribution made by chlorine dioxide ClO2. It is shown that both the current and the chlorine dioxide concentration vary in time by one and the same law corresponding to the autocatalytic redox-mediator mechanism. When the current passes through a sharp maximum typical of this mechanism, a considerable part of the total concentration of chlorine atoms in the system pertains to chlorine dioxide; hence, this component plays the key role in the process of chlorate electroreduction. The virtually complete conversion of initial chlorate to chloride is observed. [ABSTRACT FROM AUTHOR]