Interactions between fine subbituminous coal particles and micron size bubbles generated by hydrodynamic cavitation were investigated. The experimental results showed that increasing fluid velocity increases the number counts of micron size bubbles. The number counts of microns size bubbles were found to increase with increasing the dissolved gas content. At a given fluid flow velocity, reducing the dissolved gas content by heating the liquid for 2 h at 80 degrees C reduced the number counts of micron size bubbles while saturating the liquid with CO2 led to a significant increase in the number counts of micron size bubbles. However, change in fluid velocity or dissolved gas content had little effect on the bubble size. Introducing micron size bubbles generated by hydrodynamic cavitation into flotation column was found to be a promising method to enhance the recovery of fine coal particles. The micron size bubbles were found to attach to the solids with contact angle of 45 or larger. The micron size bubbles frosted on the solid surface were proven to enhance the bubble-solid attachment. These findings further improved our understanding of the role of hydrodynamic cavitation in the attachment of flotation size bubbles to gas-nucleated fine particles and hence in fine particle flotation. The conclusions derived from this study provide scientific basis for the design of hydrodynamic cavitation assisted flotation devices. (C) 2015 Elsevier Ltd. All rights reserved.