The fundamental phenomena of nanobubbles and their behavior in wastewater treatment technologies

The importance of nanobubbles is widely acknowledged, particularly in terms of their role with respect to bubble size and stability. Nanobubbles are tiny spherical cap-shaped bubbles, and have several unique physical and mechanical characteristics. Longevity, virtual disappearance of buoyancy, high internal pressure, extremely large surface/volume ratio, high oxygen dissolution rate, and generation of free radicals are the important features of nanobubbles. Their peculiar characteristics have led to many applications in the various fields of science and technology, including industrial, biological, and medical fields. This paper aims to provide a state-of-the-art for nanobubble technology. The fundamentals about existence and stability of nanobubbles are reviewed. Understanding of zeta potential values in nanobubbles is reviewed. The current methods of generation and measurement of nanobubbles are reviewed. Finally, the current applications and promising potential applications of nanobubbles are discussed, such as application of nanobubbles in flotation technology, applications of nanobubbles as cleaning agents and applications of nanobubbles in degradation of organic pollutants. In spite of its fantastic properties, use of nanobubble technology is limited to medical applications. Therefore, the recent developments in nanobubble technology are fascinating and promising but challenging as well.