MnO2/Vulcan-Based Gas Diffusion Electrode for Mineralization of Diazo Dye in Simulated Effluent

摘要

Treatments of simulated effluent solutions containing the Reactive Black 5 (RB5) were carried out by electrochemical, photoelectrochemical, electro-Fenton and photoelectro-Fenton methods using a one-compartment cell with a boron-doped diamond anode and a 3% of manganese dioxide nanoflowers supported on a carbon Vulcan XC72 gas diffusion electrode cathode. In the photo-assisted processes, the solution was irradiated using a 40-W UVC lamp immersed in the treated solution. For Fenton-based processes, only 5 min was required to attain 95% (photoelectro-Fenton) and 93% (electro-Fenton) RB5 dye degradation. When conversion to CO2 is taken into account after 6-h treatment, electrochemical method mineralized 13% of the organic load whereas removals greater than 90% were attained using the Fenton-based processes. These completely different results can be explained by the distinct spatial availability of the generated hydroxyl radical: only near the anode surface as in electrochemical-based processes or added to those distributed across the solution bulk as in Fenton-based processes.