Effect of air pressure on the electro-generation of H2O2 and the abatement of organic pollutants in water by electro-Fenton process

The electro-generation of H2O2 and the abatement of the model organic pollutant Acid Orange 7 (AO7) in water by an electro-Fenton process were performed under moderate air pressures (up to 11 bar) for the first time to our knowledge. An increase of the pressure gave rise to a drastic enhancement of the concentration of hydrogen peroxide. In systems pressurized with air at 11 bar, the electro reduction of oxygen at a graphite cathode gave rise to a concentration of H2O2 of about 12 mM, about one order of magnitude higher than that achieved at atmospheric pressure. This result is attributed to the mass transfer intensification induced by the higher local concentration of molecular oxygen dissolved in the aqueous phase. Similarly, for electro-Fenton, a drastic increase of the TOC abatement was achieved upon increasing the air pressure. The effect of the current was also investigated in detail.