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

Abstract

In this work, the gas diffusion electrode (GDE) cathode of Vulcan XC72 carbon modified with nanoparticles of WO 2.72 (WO 2.72 / Vulcan XC72) was used for H 2 O 2 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 Fe 2+ initial content (1.00, 0.50 and 0.25 mmol L-1). The WO 2.72 / Vulcan XC72 GDE electrolyzed approximately 3 times more H 2 O 2 than the Vulcan XC72 GDE. Decolorizations and mineralizations of the dye solutions were more efficient at higher concentrations of Fe 2+. The decolorization decay showed pseudo-first-order kinetics. The most promising decolorization results obtained at processes of WO 2.72 / 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 Fe 2+ , respectively). The best mineralization achieved in trials of WO 2.72 / 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.

Cobalt mediated electro-scrubbers for the degradation of gaseous perchloroethylene

“…Indirect processes can be promoted from oxygen or salts contained in the electrolyte that lead to the formation of species such as hydrogen peroxide (Paz et al, 2019;Souza et al, 2019), ozone (García-Morales et al, 2013), peroxosulphates (Balaji et al, 2015;Wacławek et al, 2017;Wang and Wang, 2018) , peroxophosphates and active chlorine species (de Moura et al, 2015). Alternatively, indirect processes can also be promoted with the addition of metal ions such as Ag, Ce, Co, Fe and Mn to acid solutions, used as electrolytes (Govindan et al, 2012a;Govindan and Moon, 2013;Muthuraman and Moon, 2017).In these cases, the process consists of the anodic oxidation of the metal from its stable oxidation state (M Z+) to a higher oxidation state (M Z+1 ), so that later this species reacts with the pollutants, regenerating its reduced state (M Z+ ).…”