Clarification of Degradation of Aromatic Compounds by Oxygen Microbubbles Water

Abstract

Microbubbles (MBs) are tiny bubbles with a particle size of 1 - 100 μm. It has been reported that MBs have excellent gas dissolving ability, and hydroxyl radicals are generated when microbubbles collapse in water. Therefore, we aimed to decompose persistent organic compounds using hydroxyl radicals generated by MBs collapse. In this study, we evaluated the degradation of the aromatic compounds methylene blue and salicylic acid by oxygen MBs water. Methylene blue was used as a hydroxyl radical detector, and we investigated the conditions under which hydroxyl radicals were generated most frequently. We confirmed that hydroxyl radicals were generated most frequently when oxygen MBs water generated by the gas-liquid revolving system was circulated under acidic conditions. The presence of cations such as copper and hydrogen ions affects the stability of MBs, and the shear stress caused by the swirling liquid flow is thought to promote MB crushing. Treatment of salicylic acid under these conditions reduced the Total Organic Carbon (TOC) of salicylic acid by about 40%. In addition, From the intermediate products, we confirmed that salicylic acid and hydroxyl radicals undergo substitution reactions according to the orientation of the functional group.