DBD plasma induced degradation of anionic and cationic dyes: An insight into the fragmentation pathway of dye degradation

The degradation of an anionic (Methyl Orange, MO) and a cationic (Methylene Blue, MB) dye using dielectric barrier discharge cold atmospheric plasma (DBD-CAP) was investigated. It was observed that the plasma generated reactive oxygen and nitrogen species (RONS), leading to the breakdown of dye chromophores and aromatic structures. Systematic analysis using UV–Vis spectroscopy, FTIR, and LC-MS/MS confirmed the degradation of > 97% for both dyes within 20 minutes of plasma exposure. The LC-MS/MS spectra revealed intermediate compounds and key degradation pathways, including azo bond cleavage, aromatic ring opening, and formation of aliphatic fragments. The proposed mechanism elucidates the stepwise breakdown into benign products such as CO 2 , H 2 O, and inorganic ions. The study demonstrated the potential of DBD-CAP as a green, efficient technology for industrial wastewater remediation, providing insights into plasma-induced molecular fragmentation and degradation kinetics of persistent organic pollutants. • Complete degradation of Methyl Orange & Methylene Blue in 20 min DBD-CAP treatment. • Plasma RONS take main role in degradation by breaking chromophores & rings. • Degradation follows pseudo-1st order reaction: k=0.177 min −1 (MO), 0.234 min −1 (MB). • A green, energy efficient method (energy yields ∼ 0.02 g/kWh) for dye degradation.