Mechanistic aspects of the sonoelectrochemical degradation of the reactive dye Procion blue at boron-doped diamond electrodes

Redox processes of the reactive dye, Procion Blue, at polycrystalline boron-doped diamond film electrodes, in buffered aqueous solution are studied as a function of pH, dye concentration and ultrasound treatment. Direct partial oxidation with a four electron transfer, within the solvent window up to 2.5 V vs. SCE in PBS, at pH 2 is possible. However, more extensive degradation of Procion Blue does not occur at potentials below that required for solvent decomposition. Oxidation is most easily achieved in acidic solution and at low dye concentrations, as evidence of fouling of the electrode surface was noted under more alkaline conditions and at higher dye concentrations. The dye is also found to influence redox processes which are directly associated with defect sites on the diamond electrode itself.