Degradation of aqueous atrazine using persulfate activated by electrochemical plasma coupling with microbubbles: removal mechanisms and potential applications

Persulfate (PS) activated by dielectric barrier discharge (DBD) integrated with microbubbles (MBs) was designed to decompose atrazine (ATZ) from aqueous solutions. The degradation efficiency reached 89% at a discharge power of 85W, a PS concentration of 1mM, and a air flow rate of 30mL/min after 75min treatment. Heat caused by DBD favoured ATZ removal. Besides, the effect of PS dosage, discharge power and initial pH values on ATZ removal was evaluated. The calculated energy yield revealed that it was economical and promising to treat 1L of ATZ-wastewaters. The existence of SO₄^2-, Cl^-, CO₃^2- and HCO₃^- lead to negative effects, while positive effect was observed when the presence of MBs and humic acid. The identification results of radicals and degradation intermediates suggested that multiple synergistic effects (such as heat, e_aq^- and H•) activated PS, and ¹O₂/reactive nitrogen species, •OH and SO₄^-• with contributions of 18%, 26%, and 29%, were main species attacking ATZ. ATZ degradation pathways including olefination, alkylic-oxidation, dealkylation, and dechlorination were proposed. An environment-friendly and a novel method for enhancing the PS-activation and ATZ-decomposition was provided, which fully utilised the electric-chemical conversion of DBD and high mass transfer efficiency of MBs.