Air bubble-induced detachment of polystyrene particles with different sizes from collector surfaces in a parallel plate flow chamber

Particle size was found to be an important factor in air bubble-induced det achment of colloidal particles from collector surfaces in a parallel plate flow chamber and generally polystyrene particles with a diameter of 806 nm detached less than particles with a diameter of 1400 nm. Particle detachmen t increased linearly with decreasing air bubble velocity and increasing liq uid-air interfacial tension, regardless of particle diameter. The influence of air bubble velocity and liquid-air interfacial tension upon particle de tachment was stronger on a hydrophilic collector surface than on a hydropho bic collector surface, whereas detachment was also less on positively-charg ed collector surfaces. In general, polystyrene particles with a diameter of 806 nm were less sensitive to the air bubble velocity than particles with a diameter of 1400 nm. However the larger particles were less sensitive to variations in liquid-air interfacial tension than the smaller ones. Hence, it is proposed that for larger particles, the liquid film in between the ai r bubble and the particle takes more time to thin down and form the three-p hase contact, necessary to induce a detachment force. (C) 2001 Elsevier Sci ence B.V. All rights reserved.