Free radical degradation in aqueous solution by blowing hydrogen and carbon dioxide nanobubbles

The main findings are the hydroxyl radical scavenging and the superoxide anion diminishing by mixing the carbon dioxide (CO₂) nanobubbles after hydrogen nanobubble blowing in water and alcohol aqueous solution. The nanobubbles produce the hydroxyl radical by ultrasonic waves, changing the pH and catalyst and so on, while the nanobubble is very reactive to scavenge free radicals. In this research especially hydrogen (4% H₂ in argon) and CO₂ nanobubbles have been blown into hydrogen peroxide (H₂O₂) added pure water, ethanol, and ethylene glycol aqueous solution through a porous ceramic sparger from the gas cylinder. The aqueous solutions with H₂O₂ are irradiated by ultraviolet (UV) light and the produced hydroxyl radical amount is measured with spin trapping reagent and electron spin resonance (ESR). The CO₂ nanobubble blowing extremely has reduced the hydroxyl radical in water, ethanol, and ethylene glycol aqueous solution. On the other hand, when H₂ nanobubbles are brown after CO₂ nanobubble blowing, the hydroxyl radical amount has increased. For the disinfection test, the increase of hydroxyl radicals is useful to reduce the bacteria by the observation in the agar medium. Next, when the superoxide anion solution is mixed with nanobubble containing water, ethanol, and ethylene glycol aqueous solution, H₂ nanobubble has reduced the superoxide anion slightly. The water containing both CO₂ and H₂ nanobubble reduces the superoxide anion. The less than 20% ethanol and the 30% ethylene glycol aqueous solution containing CO₂ nanobubbles generated after H₂ nanobubble blowing can diminish the superoxide anion much more. While the H₂ nanobubble blowing after CO₂ nanobubble blowing scavenges the superoxide anion slightly. The experimental results have been considered using a chemical reaction formula.