Influence of temperature on bulk nanobubble generation by ultrasonication

초록

The effects of liquid temperature on bulk nanobubbles (BNBs) generation using ultrasound was investigated. When liquid at different temperatures and relatively similar dissolved oxygen concentration (25 °C: 8.29 ppm; 50 °C: 8.11 ppm; and 75 °C: 7.78 ppm) were sonicated, a high number of negatively charged (−13 to −21 mV) BNBs were consistently generated within a few minutes. As the temperature of the liquid increased, it is expected that the concentration of BNBs considerably increased due to a lot of nucleation site and strong collapse of tiny bubbles. On the other hand, in a liquid with relatively low temperature, a high number of large bubbles were formed and the BNBs concentration considerably decreased. It is suggested that it has less nucleation sites compared to a liquid with higher temperature; thus, the bubble growth was accelerated by rectified diffusion and coalescence, owing to less nucleation sites versus dissolved gas concentration. © 2022 The Authors

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