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

Abstract

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.

Stability and Free Radical Production for CO2 and H2 in Air Nanobubbles in Ethanol Aqueous Solution

“…This reaction agreed with the literature. The existing •OH and •O2 − scavenging was reported by blowing CO2 nanobubbles after blowing H2 nanobubbles [30]. The formation of a monolayer by ethanol [12] and the arrangement of ethanol molecules on interfaces stabilize the bulk nanobubbles [13,14].…”

“…The radical production by ultrasonic wave irradiation becomes more important to produce the radicals, especially •OH in water, by comparing no irradiation and irradiation [29]. Fujita et al, 2021 reported the •OH scavenging and the •O 2 diminishing by mixing the CO 2 nanobubbles after hydrogen nanobubble blowing in water and alcohol aqueous solution [30]. As described above, the ethanol and water solutions containing nanobubbles have various characteristics and there is a possibility to produce the free radicals.…”

Nanobubble technologies: Applications in therapy from molecular to cellular level

“…Free radicals can be generated via intense sonication processes. However, this can be cancelled out by incorporating CO 2 or H 2 has radical scavengers (Fujita et al, 2021). Ozonised water (Takahashi et al, 2012) and plasma activated water (Gao et al, 2022) both generate nanobubbles with hydroxyl radials (‧OH) and are proposed to be used in wastewater treatment to degrade organic compounds and provide overall disinfection.…”

“…Separately, the gas nanobubbles have shown great potential and are therefore only natural to assume that the combination of different gases will enhance their function, allow the possibility of a chain reaction treatment. Fujita et al (2021) tested a combination of gaseous nanobubbles on bacteria, observing that the by first treating the sample with hydrogen nanobubbles, followed by carbon dioxide nanobubbles, they could control the radicals present in the solution. The authors concluded that this can be applied for disinfection.…”

Formation of a Hydrogen Radical in Hydrogen Nanobubble Water and Its Effect on Copper Toxicity in Chlorella

“…In recent years, numerous studies have demonstrated that hydrogen molecules can alleviate hydroxyl radical ( • OH)induced cytotoxicity without affecting physiologically important ROS and produce beneficial effects in many disease models. 10,11 There are several methods of hydrogen delivery into living organisms, including inhalation of hydrogen gas, 12 T h i s c o n t e n t i s injection of hydrogen-saturated saline, 13 and drinking hydrogen water. 14 Among these methods, drinking hydrogen water is the most suitable method of intake of molecular hydrogen for aquatic organisms.…”