Micro-bubble size distribution measurements by laser diffraction technique

The size distribution of microbubbles generated for the dissolved air flotation process could be assessed on a fast and reliable way by the application of laser diffraction technique. The bubble generation step could therefore be optimized, in order to decrease the size of the bubbles. Increasing air saturation pressure had a positive effect on bubble size, up to 400 kPa; higher pressures, however, had no effect. Surfactants (Flotigam and sodium oleate) significantly inhibited bubble coalescence, and higher concentrations of the reagents decrease the bubble size distribution, up to the critical micelle concentration. The mode of conditioning also had an important effect on bubble size improvement, by adding the surfactant into the pressure vessel. Overall median bubble size decreased 35% over the size distribution obtained without addition of reagent and conditioning.