VOC elimination performance and mechanisms via ozone-based advanced oxidation processes coupled with micro-nano bubbling

Liquid-phase advanced oxidation processes (AOPs) offer a promising approach for enhanced VOC removal. However, hampered by low gas-liquid mass transfer efficiency and insufficient reactive oxygen species production, the efficient elimination of hydrophobic VOCs remains a challenge. This study evaluated the enhancement of aromatic hydrocarbon elimination from gas streams by adding H 2 O 2 or peroxymonosulfate (PMS) to ozone micro-nano bubbling (O 3 /MNB) technology. Results indicated that MNB increased the O 3 mass transfer coefficient (K L a) to 0.17 min −1 , 4.9 times that of conventional macrobubbling. Under an inlet load of (16 ± 0.8) g·m −3 ·h −1 and empty bed contact time (EBCT) of 45 s, adding H 2 O 2 or PMS markedly increased VOC removal. The O 3 /MNB/H 2 O 2 system achieved removal efficiencies of 86%, 83%, and 86% for benzene, toluene, and xylene, corresponding to elimination capacities of (13.76 ± 0.69), (13.28 ± 0.66), and (13.76 ± 0.62) g·m −3 ·h −1 , respectively. In the O 3 /MNB/PMS system, the removal efficiencies for these compounds were 91%, 80%, and 83%, with elimination capacities of (14.56 ± 0.73), (12.80 ± 0.64), and (13.28 ± 0.23) g·m −3 ·h −1 , respectively. Electron paramagnetic resonance (EPR), quenching tests, and probe experiments revealed that O 3 /MNB/H 2 O 2 system primarily utilized hydroxyl radicals (•OH) and singlet oxygen ( 1 O 2 ), whereas O 3 /MNB/PMS system employed •OH and sulfate radicals (SO 4 •- ). System optimization demonstrated that the O 3 /MNB/H 2 O 2 system showed optimal performance for moderate-to-low concentration waste streams under controlled pH, while the O 3 /MNB/PMS system exhibited superior adaptability for complex, high-concentration exhausts across broad pH ranges. This work provides a theoretical basis for industrial hydrophobic VOC treatment and insights into advanced low-temperature control technologies.