Effect of solid wettability on three-phase hydrodynamic cavitation

In many modern industrial applications such as mineral flotation and water treatment, microbubbles have been used as an efficient aid for increasing the collision and attachment efficiencies and enhancing the recovery of valuable fine minerals. One technique to produce such micro-bubbles is to use the hydrodynamic cavitation process when gas cavities in water nucleate under low hydrodynamic pressure. To better understand the cavitation behavior in the presence of solids with different surface properties, we present an experimental study of a multi-phase system. The characteristics of hydrodynamic cavitation with a Venturi tube were experimentally investigated using acoustic detection. The effect of both particle and tube wall surface hydrophobicity and surface structure on the inception of hydrodynamic cavitation were considered. Results demonstrated that particles with lower wettability promoted hydrodynamic cavitation by efficiently trapping gas pockets that facilitate bubble nucleation. In addition, in the condition of low particle concentration (5 g/L) and fine particle size range (D50 < 20 mu m), parameters including size and roughness did not play a critical role in affecting cavitation inception. Finally, tests using Venturi tubes of different surface properties showed that the wall surface behaves similarly as particles. Hydrodynamic cavitation was promoted by a more hydrophobic Venturi tube which screened the effect of particle surface properties.