Electrochemical incineration of oxalic acid at boron doped diamond anodes: Role of operative parameters

The electrochemical incineration of oxalic acid (OA) at boron doped diamond (BDD) anodes was investigated both theoretically and experimentally in order to find the influence of the operative parameters on the performances of the process. Polarization curves and chronoamperometric measurements indicate the probable occurrence of a direct electrochemical oxidation of OA at the surface of the BDD anode at low pH and of a hydroxyl radical-mediated reaction at high pH. When incineration electrolyses are performed at low pH with potentiostatic alimentation, a dramatic influence of the potential is observed. In amperostatic incineration, high CE are obtained when most part of the process was under charge transfer controlled kinetics, i.e., when low current densities and high flow rates are imposed. Under these conditions no significant effect of current densities or flow rates is observed. The results obtained at low pH are in good agreement with the previsions of a model based on the assumption that, under adopted experimental conditions, the performances of the process are mainly determined by the competition between the direct oxidation of oxalic acid and the water discharge. The effect of the pH and of the supporting electrolyte was further investigated.