Air bubble-induced detachment of positively and negatively charged polystyrene particles from collector surfaces in a parallel-plate flow chamber

Electrostatic interactions between colloidal particles and collector surfaces were found to be important in particle detachment as induced by the passage of air bubbles in a parallel-plate flow chamber. Electrostatic interactions between adhering particles and passing air bubbles, however, were found to be less important. Regardless of the charge on the particles, detachment increased linearly with decreasing air bubble velocity and increasing liquid-air interfacial tension. Detachment efficiencies up to 75% could be achieved even for positively charged particles adhering to a negatively charged collector surface, provided that the velocity of the air bubble was low (2.37 mm s-1) and the tension at the liquid-air interface was high (70.08 mJ m-2). The detachment of positively charged particles was most sensitive to the air bubble velocity when adhering to a hydrophobic, negatively charged collector surface and least sensitive when adhering to a positively charged collector surface, but appeared equally sensitive to the liquid-air interfacial tension for all collector surfaces. On the other hand, the detachment of negatively charged particles was most sensitive to both the velocity of the air bubble and the tension at the liquid-air interface when adhering to a positively charged collector surface.