Parameter optimization and mechanism analysis of trichloroethylene degradation by ozone micro-nano bubble-hydrogen peroxide system

The ozone micro-nano bubble (O3-MNBs) technology, as an emerging groundwater remediation method, is still in its infancy in the research of groundwater chlorinated hydrocarbon remediation. In this study, an ozone micro-nano bubble-hydrogen peroxide (O3-MNBs-H2O2) composite system was constructed, and the degradation efficiency and mechanism of trichloroethylene (TCE) in groundwater were studied. The results show that the degradation effect of this system on TCE is significantly better than that of the single O3-MNBs technology, and the degradation rate exceeds 90%; it can maintain efficient degradation ability in a wide range of pH (3—11) and TCE concentration (12.5—200 mg·L−1); the presence of Fe2+ and Mn2+ in the solution promotes degradation, while SO42−, NO3− and PO43− inhibit degradation; other optimized degradation conditions are an ozone flow rate of 150 mL·min−1, a NaCl concentration of 200 mmol·L−1, and a hydrogen peroxide (30%) dosage of 16 mL·L−1. Through the intermediate products detected by gas chromatography-mass spectrometry (GC-MS) and theoretical analysis, two TCE degradation pathways dominated by ozone and hydroxyl radicals respectively were speculated, revealing the process of TCE being gradually mineralized through reactions such as dechlorination and double bond breakage.