Mechanistic study on 4, 4'-sulfonylbis removal with CO₂/Ar gas-liquid DBD plasma

In this study, a single dielectric barrier discharge (DBD) coaxial reactor was used to degrade 4, 4'-sulfonylbis (TBBPS) in water using greenhouse gas (CO₂) and argon as the carrier gases. The investigation focused on CO₂ conversion, reactive species formation, gas-liquid mass transfer mechanism, and degradation mechanism of TBBPS during the discharge plasma process. With the decrease of CO₂/Ar ratio in the process of plasma discharge, the emission spectrum intensity of Ar, CO₂ and excited reactive species was enhanced. This increase promoted collision and dissociation of CO₂, resulting in a series of chemical reactions that improved the production of reactive species such as ·OH, ¹O₂, H₂O₂ and O₃. These reactive species initiated a sequence of reactions with TBBPS. Results indicated that at a gas flow rate of 240 mL/min with a CO₂/Ar ratio of 1:5, both the highest CO₂ conversion rate (17.76%) and TBBPS degradation rate (94.24%) were achieved. The degradation mechanism was elucidated by determining types and contents of reactive species present in treatment liquid along with analysis of intermediate products using liquid chromatography-mass spectrometry techniques. This research provides novel insights into carbon dioxide utilization and water pollution control through dielectric barrier discharge plasma technology.