Degradation of Nitrobenzene-containing wastewater by ozone/persulfate oxidation process in a rotating packed bed

In this study, nitrobenzene was degraded using ozone/persulfate oxidation process in a rotating packed bed with semi-batch operation. NB degradation efficiencies by only using ozone or persulfate in the oxidation system were at 69.44% and 27.14%, respectively, whereas O-3/Na2S2O8 system achieved degradation efficiency at 90.59% in 30 min. It was discovered that degradation efficiency of nitrobenzene was significantly affected by initial pH, high gravity factor, addition amount of persulfate or ozone, and it achieved the highest value when pH at 10, high gravity factor at 40, and initially respective concentrations of extra added persulfate and ozone at 2.5 mmol.L-1 and 60 mg.L-1. The production of hydroxyl radicals (center dot OH) and sulfate radicals (SO4 center dot-) was directly identified in electron paramagnetic resonance tests and indirectly through capturing tests, and three ways of oxidation were determined including direct oxidation by 03, indirect oxidation by center dot OH and SO4 center dot-, within which center dot OH played a significant role in oxidation process. This study also used gas chromatography-mass spectrometry to detect the intermediates in the oxidation process, and two degradation pathways were inferred based on intermediate analysis. (C) 2019 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.