Enhanced electrocatalytic production of H2O2 at Co-based air-diffusion cathodes for the photoelectro-Fenton treatment of bronopol

Abstract

Co, S, P)-decorated multiwalled carbon nanotubes (MWCNTs) have been synthesized following a hydrothermal route as electrocatalysts to manufacture large surface area airdiffusion cathodes with carbon cloth as substrate. The enhanced electrocatalytic H2O2 production as compared with Co-free MWCNTs cathodes was demonstrated in a 2.5-L prepilot plant with either a RuO2-based or boron-doped diamond (BDD) anode, accumulating between 2-and 3-fold greater H2O2 contents with the catalyzed cathode. The good stability of this new material was ensured from the low Co leaching, with less than 9% Co released to solutions upon repeated usage. Aqueous solutions of the brominated organic preservative bronopol with 0.050 M Na2SO4 at pH 3.0 were comparatively treated by electro-oxidation (EO-H2O2), electro-Fenton (EF), UVA-assisted photoelectro-Fenton (PEF) and solar PEF (SPEF) at constant current density. SPEF with BDD anode and the catalyzed cathode showed the best performance, with total bronopol removal at 210 min and 94% mineralization after 360 min at 40 mA cm -2 , thanks to the action of • OH, BDD( • OH) and sunlight. Formic acid was identified as main reaction by-product, whereas Br and N atoms were mainly converted to Br − , BrO3 − and NO3 − . Some unidentified organic by-product containing Br and N was formed as well.

A Highly Stable Metal–Organic Framework-Engineered FeS2/C Nanocatalyst for Heterogeneous Electro-Fenton Treatment: Validation in Wastewater at Mild pH

“…In IrO2/air-diffusion cells, the optimum Fe 2+ catalyst concentration is in the range 27-55 mg L -1 . [8][9][10] Heterogeneous EF catalyzed with 0.5 g L -1 natural pyrite at initial pH 6.0 showed the lowest performance, attaining a fluoxetine concentration decay as low as 19%. Some authors have reported a fast pollutant removal by pyrite-EF, [30][31][32] but in those trials current was supplied once the spontaneous acidification and iron release had occurred.…”

Membrane Separation Coupled with Electrochemical Advanced Oxidation Processes for Organic Wastewater Treatment: A Short Review

“…In addition, the thin and porous structure of the membrane is beneficial for injected oxygen or air to seep through the pores and contact oxygen reduction reaction (ORR) active centers, which generates a large amount of H 2 O 2 . Ye et al [ 113 ] prepared Co-based air-diffusion cathodes to enhance the mass transfer function of O 2 , and they also found enhanced electrocatalytic H 2 O 2 production; moreover, the CE reached 100% at low current.…”

Stoichiometric Excess of H2O2 as Strategy of Oxidant Dosing for Intensifying Both Degradation and Mineralization of the Hydrochlorothiazide via UVCH2O2, Dark-Fenton, and Photo-Fenton

“…On the other hand, if considered a more advanced stage of the incomplete oxidation, other sorts of fragments may be found. Regarding the latest stage on the incomplete oxidation, organic acids of short-chair such as maleic acid, [14] oxalic acid, [15], and formic acid [16] have been identified for micropollutants in general. For this case, the stoichiometric oxidant quantity needed is far higher than half of that micropollutant quantity.…”