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

Zhenyao Han,Akira Otsuki,Yuezou Wei,Toyohisa Fujita,Kaituo Wang,Hiromi Kurokawa,Chunlin He,Hirofumi Matsui,Gjergj Dodbiba

doi:10.3390/nano12020237

Abstract

In this study, 8% hydrogen (H2) in argon (Ar) and carbon dioxide (CO2) gas nanobubbles was produced at 10, 30, and 50 vol.% of ethanol aqueous solution by the high-speed agitation method with gas. They became stable for a long period (for instance, 20 days), having a high negative zeta potential (−40 to −50 mV) at alkaline near pH 9, especially for 10 vol.% of ethanol aqueous solution. The extended Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory was used to evaluate the nanobubble stability. When the nanobubble in ethanol alkaline aqueous solution changed to an acidic pH of around 5, the zeta potential of nanobubbles was almost zero and the decrease in the number of nanobubbles was identified by the particle trajectory method (Nano site). The collapsed nanobubbles at zero charge were detected thanks to the presence of few free radicals using G-CYPMPO spin trap reagent in electron spin resonance (ESR) spectroscopy. The free radicals produced were superoxide anions at collapsed 8%H2 in Ar nanobubbles and hydroxyl radicals at collapsed CO2 nanobubbles. On the other hand, the collapse of mixed CO2 and H2 in Ar nanobubble showed no free radicals. The possible presence of long-term stable nanobubbles and the absence of free radicals for mixed H2 and CO2 nanobubble would be useful to understand the beverage quality.

Highlights

2) gas nanobubbles agitation method with gas injection, and the main findings were as follows: ethanol were produced at 10, 30, and 50 vol.% ethanol aqueous solution by the high s agitation method with injection, theowing main findings were as follows: The prepared nanobubbles weregas stable for 20and days to a high negative zeta potential at pH 9. nanobubbles were stable for 20 days owing to a high negative zeta
ConclusionThe 8% hydrogen (H2 ) in argon (Ar) and carbon dioxide (CO2 ) gas nanobubbles with ethanol were produced30, and 50 ethanol solution by the speed The at (Hvol.%2) in argon (Ar)aqueous and carbon dioxide (COhigh2) gas nanobubbles agitation method with gas injection, and the main findings were as follows: ethanol were produced at 10, 30, and 50 vol.% ethanol aqueous solution by the high s agitation method with injection, theowing main findings were as follows: The prepared nanobubbles weregas stable for 20and days to a high negative zeta potential at pH 9. nanobubbles were stable for 20 days owing to a high negative zeta alkaline The preparedWhen the pH of ethanol alkalinepH aqueous solution with nanobubbles was adjusted tential at alkaline to acidic at the potential nanobubbles was almost zero

Summary

Introduction

There have been many reports on bulk nanobubbles or nanoparticles in ethanol aqueous solution. The object of nanobubbles in ethanol solution was hydrogen in argon and carbon dioxide gas nanobubbles. There are some reports on the exsistence of imputities in bulk ethanol nanobubbles. They were first introduced and the other reports on the stability of nanobubbles in ethanol were discussed

Methods

Results

Conclusion