Enhanced generation of active oxygen species induced by O-3 fine bubble formation and its application to organic compound degradation

By using O-3 fine bubbles that promote the mass transfer of O-3 to the liquid phase and the conversion of the dissolved O-3 into active oxygen species with a high oxidation potential, an improved liquid-phase oxidation technique was developed to accelerate the degradation of an organic compound at a constant O-3 flow rate. By the use of a dielectric-barrier-discharge reactor, O-2 was converted into O-3 at an O-2 flow rate of 0.56 mmol/(L center dot min), with 5 mol% O-2-to-O-3 conversion. Using a self-supporting bubble generator, O-3 bubbles with an average diameter (d(bbl)) of 50 mu m were continuously supplied into a solution in TBA (OH center dot scavenger) at 303 K, and the TBA being degraded. For comparison, O-3 bubbles with d(bbl) values of 200-5000 mu m were obtained using a dispersing-type generator. It was found that the minimization of bubble diameter accelerated both O-3 dissolution, as a consequence of the increase in the gas-liquid interfacial area and the residence time of the bubbles, and enhanced OH center dot generation, because of the increase in contact probability between dissolved O-3 and OH- at the minute gas-liquid interfaces, caused by the accumulation of OH- around the fine bubble surfaces. To ascertain the influence on organic compound degradation of the improved oxidation potential, bisphenol A, as a model compound, was degraded by O-3 bubble injection at different d(bbl) values. Sequentially, the high OH center dot selectivity obtained by minimizing the bubble diameter can effectively achieve the rapid degradation of organic compounds and intermediates under a constant O-3 flow rate. [GRAPHICS] .