Nano bubbles Size Measurement Using Laser Diffraction Technique

In this paper, size distribution of nano-microbubbles produced by a nano-micro bubble generator was measured by the reliable and fast method of laser diffraction. The effects of key parameters including time, type and concentration of frother, gas flow rate and gas type on size distribution of nano-microbubbles were investigated. Measurement results of nano-microbubble size as a function of time showed that simultaneously with the reduction of the absolute zeta potential of nano-microbubbles and the amount of dissolved oxygen in the solution, size of nano-microbubbles was decreased. Increased concentration of frother as well as affecting conventional sized bubbles reduced the average size of nano-microbubbles. Results also showed that the nanobubbles produced with Aerofroth65 were smaller than those formed with MIBC and Pine oil. This is because surface tension reduction by Aerofroth65 is more significant than by MIBC and Pine oil. Increased aeration rate (air and oxygen) from 0.1 to 0.3 l min-1, reduced the average size of nano-microbubbles. Nano-microbubbles generated in the presence of oxygen had smaller average size relative to air nano-microbubbles because of higher dissolution of oxygen in water in comparison with air and also the higher absolute value of surface zeta potential.