Hydrogen Peroxide Electrogeneration by Gas Diffusion Electrode Modified With Tungsten Oxide Nanoparticles for Degradation of Orange II and Sunset Yellow FCF Azo Dyes

In this work, the gas diffusion electrode (GDE) cathode of Vulcan XC72 carbon modified with nanoparticles of WO2.72 (WO2.72 / Vulcan XC72) was used for H2O2 electrogeneration and degradation of 350 mL of Orange II (OII) and Sunset Yellow FCF (SY) azo dyes by electro-Fenton (EF) and photoelectro-Fenton (PEF) processes with different Fe2+ initial content (1.00, 0.50 and 0.25 mmol L-1). The WO2.72 / Vulcan XC72 GDE electrolyzed approximately 3 times more H2O2 than the Vulcan XC72 GDE. Decolorizations and mineralizations of the dye solutions were more efficient at higher concentrations of Fe2+. The decolorization decay showed pseudo-first-order kinetics. The most promising decolorization results obtained at processes of WO2.72 / Vulcan XC72 cathode combined with Pt anode (100% color removal of OII and SY at 30 and 20 min of electrolysis with 1.00 mmol L-1 Fe2+, respectively). The best mineralization achieved in trials of WO2.72 / Vulcan XC72 cathode combined with boron-doped diamond (BDD) anode (82% total organic carbon (TOC) removal of OII by PEF / 1.00 after 3 h and 90% TOC removal of SY by PEF / 0.50 after 4 h). It was found that SY decolorization was faster and mineralization showed a similar yield independent of oxidized dye.