Synergistic degradation of trans-ferulic acid in aqueous solution by dielectric barrier discharge plasma combined with ozone.

Trans-ferulic acid (FA), extensively used in pharmaceutical and olive oil industries, causes huge risks to ecological environment due to its biotoxicity and phytotoxicity, leading to the difficulty of biochemical processes in treating FA wastewater. In this study, synergistic degradation of FA via dielectric barrier discharge (DBD) plasma and O3 (plasma-ozone) was studied. The results showed that FA degradation efficiency reached 96.9% after a 40-min treatment by plasma-ozone process, and the energy efficiency of FA degradation was increased by 62.5 and 24.5% compared to single DBD plasma and ozonation treatment. Moreover, FA degradation rate constant in plasma-ozone process was 41% higher compared with the sum of single DBD plasma and ozonation, indicating a significant synergistic effect. Radical diagnosis experiments reveal that a profound increase of ·OH yield through peroxone (H2O2/O3) and UV/O3 pathways is the important mechanism of synergistic degradation of FA in plasma-ozone process, while eaq- played little role in FA degradation. A degradation pathway of FA by plasma-ozone was also proposed according to the detected intermediates from EEM and LC-MS. This work revealed that plasma-ozone process is an alternative process for FA treatment, and the findings are helpful for understanding FA degradation characteristics and synergistic mechanisms in plasma-ozone process.