Hydrogen peroxide is used to oxidize the remaining cyanide in the effluents of precious metal leaching plants. This document presents the electrochemical characterization of the reduction of dissolved oxygen to produce hydrogen peroxide. Evaluating this reaction allowed to understand the fundamentals of the process to develop an “in-site” operation to produce the oxidizing agent. This technology consists of using the activated carbon surface to catalyse the reduction of dissolved oxygen. To achieve this, the electroreduction of dissolved oxygen at different conditions was characterized by cyclic voltammetry and factors such as concentration of oxygen and pH were evaluated. According to the results, the reduction of dissolved oxygen is unstable at alkaline conditions (i.e., pH 13) since oxidation and reduction reactions occur simultaneously. Otherwise, reduction is stable at acid conditions (i.e., pH 3), and it is carried out in a potential range between 200 and 400 mV. Dissolved oxygen concentration (i.e., 6.4, 3.6, and 0.5 mg/L) has a significant effect on electric current when the potential is swept in the negative direction at pH 3.

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