The so-called micro-nano-bubble, refers to the bubble occurs when the diameter of about 10 microns to hundreds of nanometers between the bubbles, this bubble is between the micro-bubbles and nano-bubbles, with conventional bubbles do not have the physical and chemical properties .
  1. Large surface area

The relationship between the volume of the bubble and the surface area can be expressed by the formula. The formula of the volume of the bubble is V = 4π / 3r3, the surface area formula of the bubble is A = 4πr2, the two formulas are combined to get A = 3V / r, namely V = nA = 3V / r. That is, the total surface area of the bubble is inversely proportional to the diameter of a single bubble in the case of a constant volume (V constant). According to the formula, the specific surface area of the former is about 100 times larger than that of the latter in the case of a volume of 10 μm compared to a bubble of 1 mm. Air and water contact area increased by 100 times, a variety of reaction speed has increased by 100 times.

2. Rise slowly

According to Stokes' law, the rate of bubble rise in water is proportional to the square of the bubble diameter. The smaller the bubble diameter is, the slower the air bubble rises. From the relationship between the bubble rising speed and the diameter of the bubble, it can be seen that the velocity of the bubble with the bubble diameter of 1 mm in the water is 6 m / min, and the velocity of the bubble with diameter of 10 m in the water is 3 mm / min, . If taking into account the increase in specific surface area, micro-nano-bubble dissolution capacity than the average air increased by 200,000 times.

3. Self-pressurized dissolved

There is a gas-liquid interface around the bubbles in the water, and the existence of the gas-liquid interface causes the bubbles to be affected by the surface tension of the water. For a bubble having a spherical interface, the surface tension can compress the gas in the bubble, so that more gas in the bubble dissolves into the water. According to the Young-Laplace equation, ΔP = 2σ / r, ΔP represents the pressure rise value, σ represents the surface tension, and r represents the bubble radius. A bubble having a diameter of 0.1 mm or more can be negligible, while a fine bubble having a diameter of 10 m is subjected to a pressure of 0.3 atm and a bubble having a diameter of 1 m is subjected to a pressure of up to 3 atm. The dissolution of micro-nanobubbles in water is a gradual process of bubble reduction. The pressure increase will increase the dissolution rate of gas. Along with the increase of specific surface area, the speed of bubble shrink becomes faster and faster, and finally dissolves into water, Theoretically the bubble is about to disappear when the pressure is infinite.

4. Surface charged

Pure water solution is composed of water molecules and a small amount of ionized H + and OH- formed in the gas-liquid interface in the formation of the gas-liquid interface has the characteristics of easy to accept H + and OH-, and the cation is usually easier than the anion gas-liquid interface, leaving the interface Often with a negative charge. Charged surfaces tend to adsorb counterions, particularly counter-ions, in the medium, creating a stable double layer. The potential difference caused by the surface charges of microbubbles is often characterized by zeta potential, which is an important factor determining the adsorption performance of the bubble interface. When the micro-nano-bubbles shrink in water, the charge ions are concentrated and concentrated at the very narrow bubble interface, which shows a remarkable increase of zeta potential, and a very high zeta potential at the interface before bubble burst.

5. produce a large number of free radicals

Micro-bubble burst moment, due to the dramatic changes in gas-liquid interface disappear, the interface of high concentrations of ions will accumulate chemical energy released at once, at this time can stimulate the production of a large number of hydroxyl radicals. Hydroxyl radicals have a high redox potential, the resulting superoxide oxidation can degrade the water under normal conditions difficult to oxidative decomposition of pollutants such as phenol, to achieve the purification of water quality.

 6. High mass transfer efficiency

Gas-liquid mass transfer is the rate-limiting step of many chemical and biochemical processes. The results show that the gas - liquid mass transfer rate and efficiency are inversely proportional to bubble diameter and the micro - bubble diameter is very small, which has obvious advantages over conventional bubbles in mass transfer. When the bubble diameter is small, the surface tension at the micro-bubble interface has a significant effect on the bubble characteristics. At this time the surface tension on the internal gas produced a compression effect, making the micro-bubble in the process of increasing shrinkage and show their own pressurization effect. In theory, with the infinite narrowing of the bubble diameter, the specific surface area of ​​the bubble interface will increase infinitely, and finally the internal pressure can be increased to infinity due to the self-pressurization effect. Therefore, as the specific surface area and the internal gas pressure increase, the more bubbles are dissolved in the water interface through the bubble interface, and the effect of the surface tension is also decreased with the decrease of bubble diameter. More and more obvious, the final internal pressure reaches a certain limit and causes the bubble interface rupture disappears. Therefore, this self-pressurization characteristic of the micro-bubble during the shrinkage process enables the mass transfer efficiency to be continuously enhanced at the gas-liquid interface, and this property allows the micro-bubble to be maintained even when the gas content in the water body reaches the supersaturation condition The gas mass transfer process is continued and efficient mass transfer efficiency is maintained.

 7. High gas dissolution rate

The micro - nanobubbles have the characteristics of slow - rising and self - pressurization, which make the micro - nanometer bubbles gradually reduce to nano - scale in the process of slow rising, and finally reduce the annihilation into the water, which can greatly improve the gas (air, oxygen, ozone, Carbon dioxide, etc.) in water solubility. For ordinary air bubbles, the solubility of the gas is often affected by ambient pressure and limits the existence of saturated solubility. In the standard environment, the solubility of the gas is difficult to reach saturation solubility above. The micro-nano-bubble pressure is higher than the pressure inside the environment, making the atmospheric conditions for the assumption that the gas supersaturated solution conditions can be broken.