Nano Bubble Process

The Definition Of Nanobubble

In general, microbubble refers to the size less than 50 µm (1 µm = 0.001 mm), and 1 µm is 1,000 nm. Nanobubble refers to less than 1 µm that is not visible, and nano is the unit indicating 1/1 billion. 1 nm refers to 1 m of 1 billion; in other words, it is 1 strand of 10,000 strands of hair and the size of 3–4 atoms. In the blood, the size of the red blood cell is 6–8 µm, the white blood cell is 12–25 µm, and the skin pore is about 25 µm.

 

The Basics

The technique of blowing air into liquid has been practiced for years in various fields including waste water treatment, but in most cases, the bubbles were as big as several centimeters or tens of centimeters in diameter.
There is no problem to proceed with large bubbles for your operational process. But the recent focus on the environment and energy efficiency and the rising demand for more efficient and functional process technologies are turning the spotlight on these tiny bubbles.

Tiny Bubbles, Ultra Fine Bubbles, Micro-Nano-Bubble

Ultra fine bubbles are called in several ways such as “micro bubbles,” “nano bubbles,” or “micro-nano-bubbles” with a prefix indicasting the bubble size, but their definitions vary from each researchers and companies.

On ultra fine bubbles, many studies have been published to date, most of which generally agree that bubbles smaller than 50μm in diameter have properties different from larger ones. Researchers are beginning to suggest that bubbles smaller (assuming 1μm or 0.1μm as a threshold) than that have even more unique properties, which remain not yet fully explained.

We refrain from using the designation of “nano bubbles” (bubbles with diameters of tens or hundreds of nano meters in our definition), because we have not yet established a method to directly measure and verify a bubble diameter of that class: we use instead designations such as “micro bubbles” or “micro-nano-bubbles” to indicate a broader definition, since we can only infer, based on bubble distribution charts summarizing optically verified bubbles, that there must be a certain share of bubbles under our current limit of measurement (i.e. smaller than 1μm).
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Why Tiny Bubbles?

Although many academic institutions and companies have been working on the research, many aspects are yet unknown to wait for future study.
Here, we will show you the general characteristics of micro/nano bubbles and their advantages.
１．Sustained effects over a wide area
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The buoyancy of a bubble is proportional to the volume of air contained in it.
Smaller bubbles have smaller buoyancy. Thus, micro/nano bubbles have minimal buoyancy and able to survive underwater longer than larger bubbles.

Force of buoyancy: F = pVg （p: Fluid density, V: Volume of the object, g: Gravitational acceleration）
２．Better reactivity (larger contact area between air and liquid)



When one square mm of water is filled with micro bubbles (1μm in diameter), the contact area between water and bubbles are 1000 times as large as that in water filled with normal bubbles (1mm diameter). The increase in the contact area dramatically enhances aerobic bacteria activities in the liquid and the efficiency of chemical reaction between the supplied gas and liquid ingredients.
３．Promotion of separation by floatation



As bubbles float up to the surface, they catch solids (contaminants) suspended in the liquid and bring them up to the surface. Since suspended solids are not uniform in size and shape, large bubbles often fail to catch and bring them up to the surface. On the other hand, micro/nano bubbles can penetrate into small dents of a contaminant and enclose it entirely in a ball of tiny bubbles, making it buoyant.



４．Lower surface tension (higher detergency from better soaking)



The surface tension of liquid is proportional to the density of the liquid. Introducing micro/nano bubbles into liquid lowers the apparent density of the liquid, resulting in better soaking and detergency.