Kaneo Chiba

Enhanced free-radical generation by shrinking microbubbles using a copper catalyst

Free-radicals are generated by collapsing microbubbles in aqueous solutions; however, the concentration is too low to be of practical use. In this study, copper was found to enhance the generation of hydroxyl radicals from collapsing oxygen microbubbles under acidic conditions through electron-spin-resonance spectroscopy analysis. Moreover, the degradation of polyvinyl alcohol, which is not decomposed even by ozone, was also observed during the collapse of the air microbubbles. These findings greatly increase the potential of the microbubble-collapse technique for use in the field of wastewater treatment.

Degradation of phenol by the collapse of microbubbles

This study focuses on the application of microbubble collapse technique to the wastewater treatment. We have verified that collapsing air microbubbles lead to the decomposition of phenol, a common pollutant. A reduction in phenol of approximately 60% was observed during a 2-h test period when air was used as the microbubble source. We have also studied the dependence of phenol degradation on the pH of the solution and the type of gas within the microbubbles. The pseudo-first-order kinetic constant for the degradation of phenol, k, increased linearly with the concentration of H(+) in solution. The use of oxygen microbubbles gave rise to the highest k value (1.6h(-1)) measured. It is suggested that hydroxyl radicals play an important role in the phenol decomposition process. The acquired information would be useful for the future application of microbubbles in the field of wastewater treatment.