BUBBLE-PARTICLE ATTACHMENT

Bubble-particle attachment efficiencies have been determined by measur ing the collection efficiencies of single bubbles, with diameters betw een 0.75 and 2.0 mm and methylated quartz particles, whose diameters r anged from 5 to 80 mu m, as a function of particle-water advancing con tact angle and ionic strength. By performing experiments under conditi ons where the bubble-particle aggregate was stable and using a model f or collision efficiency, both attachment efficiency and induction time were calculated. Smaller bubbles have larger attachment efficiencies than do larger bubbles for all particle sizes over a wide range of con tact angles and ionic strengths. Induction times generally decrease wi th increasing attachment efficiency, except for fine particles with di ameters less than about 10 mu m, where they increase. Induction-time t rends may be qualitatively interpreted in terms of thin-film drainage time as well as the time of formation of a stable wetting perimeter. T he elementary steps in the bubble-particle attachment process are not properly described by existing models.