Synergistic degradation of trans-ferulic acid by water falling film DBD plasma coupled with cobalt oxyhydroxide: Performance and mechanisms

In this study, trans-ferulic acid (FA) was degraded by water falling film dielectric barrier discharge (DBD) plasma coupled with CoOOH catalyst. The results reveal that CoOOH improved the degradation of FA by DBD plasma through an apparent catalytic effect. 98.2% of FA was degraded in 10 min by DBD + CoOOH (0.5 g/L dosage) system at 11.2 kV applied voltage, which was 23.8% higher than that in a sole DBD system; the corresponding energy yield (G(50)) was increased by 186% and the synergistic intensity for FA degradation reached up to 2.76. The evolution of reactive species reveals that the synergistic effect of DBD plasma and CoOOH catalyst can be attributed to the catalytic conversion of O-3 and H2O2 into center dot OH on the active sites of CoOOH surface. The results of Lewis acid sites, X-ray photoelectron spectroscopy and Raman spectroscopy suggest that the abundant oxygen vacancies and Lewis acid sites, which are offered by the lattice -OH groups in CoOOH, serve as the catalytic active sites of CoOOH. According to the detected byproducts by liquid chromatograph/mass spectrometer, a possible FA degradation pathway was also tentatively proposed.