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.

DC generated Ar–CO₂ discharge for plasma mixtures at 2.0 Torr is investigated to evaluate the variation in the electron temperature and density, electron energy distribution function, and population densities of the reactive atomic, molecular, and ionic species of CO₂–Ar plasmas as a function of the Ar percentage in the mixtures. Optical emission spectroscopy and quadrupole mass spectrometry are used to determine the reactive species in the Ar–CO₂ plasma in the DC discharge mode as a function of the Ar percentage. The species observed in the plasma mixtures were CO₂, O₂, CO, O, C₂, and Ar, which agree very well with the mass spectroscopy observation. In addition, single Langmuir probes are employed to characterize the plasma. The CO species are observed to increase to 40% Ar in the mixture and then decrease. The electron temperatures and density are found to be between 1.9-3.1 eV and (0.8–2.0) × 10¹⁰cm⁻³, respectively.