Comparative study of DBD plasma bubbles and corona discharge bubbles for atrazine degradation in water: From process optimization to degradation pathways

This study explores, for the first time, the degradation of atrazine in water using nanosecond-pulsed underwater plasma bubble reactors. Two configurations, dielectric barrier discharge (DBD) bubbles and corona discharge bubbles, were comparatively assessed. Beyond reactor design, the effects of plasma gas composition, water matrix, and initial atrazine concentration were systematically examined. The physicochemical properties of plasma-activated water were characterized and correlated with degradation performance and energy efficiency. The DBD bubble reactor outperformed the corona bubble system, owing to its ability to generate higher concentrations of short-lived reactive species. Under optimized conditions, the DBD system achieved over 99 % atrazine removal within 40 min, with an electrical energy per order (E EO ) as low as 1.6 kWh/m 3 . Reactive species analysis and scavenging experiments demonstrated that short-lived species, particularly singlet oxygen ( 1 O 2 ) and hydroxyl radicals (·OH), were the most dominant contributors to atrazine breakdown. In total, ten transformation products of atrazine were identified using liquid chromatography–high-resolution mass spectrometry (LC-HRMS). A degradation pathway was proposed, with dealkylation, oxidation, and dechlorination identified as the main transformation processes. The formation and evolution of byproducts were also tracked in both ultrapure and tap water matrices, and total organic carbon (TOC) measurements confirmed substantial mineralization. The in-house risk assessment program, ToxTrAMs was used for the prediction of the toxicity of atrazine and its identified TPs, uncovering that most of the identified TPs exhibited lower toxicity than the parent compound. These results underscore the potential of plasma bubble technology, particularly DBD-based systems, as a promising and energy-efficient solution for the removal of persistent pesticides from water. • DBD plasma bubbles outperform corona for atrazine degradation in all conditions. • DBD bubbles favor short-lived ROS; corona bubbles enhance long-lived species. • Atrazine degradation is mainly driven by ·OH and 1 O 2 , not RNS species. • Ten byproducts identified; degradation involves dealkylation, oxidation, dechlorination. • DBD plasma bubbles achieved high efficiency with E EO as low as 1.6 kWh/m 3 .