Application of Photoelectro-Fenton/BDD Process Based on the Cathodic Production of H2O2 for Degradation of Industrial Dyes

Photoelectro-Fenton/BDD process promotes in situ hydrogen peroxide (H₂O₂) by means of oxygen reduction via two electrons, adding Fe²⁺ to the solution resulting in the production of free hydroxyl radicals (^•OH). The reaction can be catalyzed by the UV ligth accelerating the degradation of organic compounds in solution, because it promotes the photocehmical regeneration of Fe²⁺, and as a result a major ^•OH radicals production. In the present work, the authors discussed the study of the H₂O₂ production over boron doped diamond (BDD) cathode and the degradation of two industrial azo dyes, Blue-BR (B-BR) and Black-TRS (B-TRS) by photoelectro-Fenton/BDD (PEF/BDD) process using UV-ligth source. Comparative electrolyses carried out with 3L filter press pilot plant equipped with a BDD anode and cathode at constant current density showed the superiority of the processes with BDD because of the higher oxidation ability of ^·OH formed from water oxidation at the BDD surface. Total mineralization was rapidly reached for the most potent treatment of PEF with BDD due to the additional oxidation by ^·OH produced from Fenton's type reaction between added Fe²⁺ (0.5mM) and H₂O₂ generated at the cathode. Azo dyes decay always followed a pseudo-first-order kinetics. The influence of current density and substrate concentration on PEF with BDD was examined.