Zeta-potential of Micro- and/or Nano-bubbles in Water Produced by Some Kinds of Gases

Several reports in the literature show the acceleration in the physiological activity in plants and shellfishes when water containing micro- and nano-bubbles was used. However, the mechanisms of the phenomenon relating to aqua and agricultural fields and the stability of micro- and nano-bubbles in water have not been explained scientifically yet. The reason is the lack of knowledge about the characteristics of water containing micro- and nano-bubbles. In order to understand these characteristics, ξ-potential measurements were done in water after the generation of micro- and nano-bubbles using different kinds of gases. The values of ξ-potential were all negative and the absolute values were in the range between 34-45 mV (oxygen), 17-20 mV (air), 29-35 mV (nitrogen), 20-27 mV (carbon dioxide), and 11-22 mV (xenon). The different absolute values of ξ-potential may indicate different stability of the nano-bubbles according to the type of gas, as well as different structures at the gas-liquid interface. Furthermore, the bubbling time seemed to affect the ξ-potential, but more studies are needed to understand the phenomena during the production of micro- and nano-bubbles.