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Currently, azo dye Carmoisine is an additive that is widely used in the food processing industry sector. However, limited biodegradability in the environment has become a major concern regarding the removal of azo dye. In this study, the degradation of azo dye Carmoisine (acid red 14) in an aqueous solution was studied by using a sequenced process of electro-oxidation–plasma at atmospheric pressure (EO–PAP). Both the efficiency and effectiveness of the process were compared individually. To ascertain the behavior of azo dye Carmoisine over the degradation process, the variations in its physical characteristics were analyzed with a voltage–current relationship, optical emission spectra (OES) and temperature. On the other hand, chemical variables were analyzed by finding out pH, electrical conductivity, absorbance (UV/VIS Spectrophotometry), chemical oxygen demand (COD), cyclic voltammetry (CV), energy consumption and cost. The sequenced process (EO–PAP) increased degradation efficiency, reaching 100% for azo dye Carmoisine (acid red 14) in 60 min. It was observed that the introduction of small quantities of iron metal ions (Fe2+/Fe3+) as catalysts into the plasma process and the hydrogen peroxide formed in plasma electrical discharge led to the formation of larger amounts of hydroxyl radicals, thus promoting a better performance in the degradation of azo dye. This sequenced process increased the decolorization process.

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Phenolic pollutants are recalcitrant substances that cannot be removed from wastewater using the current treatments. In this study, degradation of phenolic pollutants was studied on the basis of the application of hydrogen peroxide during the electrooxidation process using BDD as anode (EO−H2O2 coupled process). The process was optimized using 4‐chlorophenol (4‐CP) as model compound and later an emerging pollutant, Nonylphenol Ethoxylate‐10 (NP10EO), was degraded using the optimized experimental conditions found. To ascertain treatment effectiveness, experiments with hydrogen peroxide (H2O2), electrooxidation (EO) and EO−H2O2 (coupled process) were carried out. The variables considered in this investigation were pH, current density, quantity of H2O2, and reaction time. It was observed that the coupled process (EO−H2O2) increases degradation efficiency, reaching 81.9 % for 4‐CP and 94.3 % for NP10EO. UV/VIS spectrophotometry, COD and HPLC analysis verified these results. The results of the analysis by cyclic voltammetry after the EO−H2O2 coupled process indicate that pollutants in the solution were efficiently oxidized. It was concluded that small amounts of hydrogen peroxide (250 μL 30 % w/v solution per 1.1 L) are sufficient to attain good results; larger amounts of H2O2 produce inhibitory effects during degradation. The slow cathode (SS) oxidation during the experiments was confirmed by XPS and AFM analysis.