Abstract
The method of making OH radicals generated by the collapse of ultrafine bubbles as an indicator when applying ultrasound was examined as the method of identifying ultrafine bubbles less than 1 μm in diameter under the presence of mixed solid nanoparticles. First, potassium iodide (KI) method was used to evaluate OH radicals. Since difference in absorbance due to OH radicals generated by the collapse of ultrafine bubbles is very small when using air as contained gas, evaluation using the KI method was difficult; however, a distinct difference in absorbance was confirmed by increasing the amount of OH radicals generated by using ozone as contained gas. Moreover, the higher the ultrasound frequency, the greater the difference in absorbance. On the other hand, a luminescence phenomenon related to the collapse of ultrafine bubbles by ultrasound was confirmed with sonoluminescence observation, confirming further that the luminescence intensity of water added with solid particles of the same diameter and number density as those of ultrafine bubbles is smaller than that of ultrafine bubble water.
Highlights
The International Standardization (ISO) has defined to call air bubbles with less than 100 μm diameter, which were hitherto called micro-nano bubbles, as "fine bubbles" whose breakdown: "microbubbles" with 1 to 100 μm diameter and "ultrafine bubble" with less than 1 μm diameter
When air was used as the introduced gas, the absorption wavelength indicating I3- was observed in the ultrafine bubble water to which ultrasound was applied, confirming the possibility of an evaluation for the presence of ultrafine bubbles using the KI method by making the OH radicals as an index; on the other hand, its degree of difference was very small, making it difficult to judge the clear difference in the absorbance
The method of making OH radicals generated by the collapse of ultrafine bubbles as an indicator when applying ultrasound was examined as the method of identifying ultrafine bubbles less than 1 μm in diameter under the presence of mixed solid nanoparticles
Summary
The International Standardization (ISO) has defined to call air bubbles with less than 100 μm diameter, which were hitherto called micro-nano bubbles, as "fine bubbles" whose breakdown: "microbubbles" with 1 to 100 μm diameter and "ultrafine bubble" with less than 1 μm diameter. In order to meet this requirement, a resonance mass measurement method capable of distinguishing between particles with positive and negative buoyancy using the specific frequency of substance was proposed This method judges as ultrafine bubbles by regarding that particles with positive buoyancy are lighter than water; since the weight of impurities is not uniform, it is not possible to regard all the particles with positive buoyancy as ultrafine bubbles. It becomes necessary and important to develop an analysis technology capable of identifying only ultrafine bubbles even in the presence of impurities For this reason, a method of applying ultrasound to ultrafine bubble water to evaluate the presence of. OH radicals generated from ultrafine bubbles collapsed by the application of ultrasound were evaluated from the absorbance measurement using potassium iodide and the behavior observation of sonoluminescence
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