Particle-bubble attachment in mineral flotation

Attachment efficiencies of rough, angular, methylated quartz particles with nitrogen bubbles are derived from experimental capture efficiency data in conjunction with a collision model termed the Generalized Sutherland Equati on (GSE). The methylated quartz particles ranged in size from 7.5 to 70 mu m equivalent diameter and had advancing contact angles between 33 degrees a nd 74 degrees. They heterocoagulated with nitrogen bubbles between 0.77 and 1.52 mm in diameter in 0, 0.01, or 0.1 mol dm(-3) KCl. The attachment effi ciencies decreased with increasing particle size and bubble size, but incre ased with particle contact angle and KCl electrolyte concentration. These a ttachment efficiency data were then used to test the Dobby-Finch attachment model for potential flow conditions. The latter model was modified so that the conditions of approach of the particle toward the bubble surface are t he same as those defined previously in the GSE collision model (Dai et at, 1998, J. Colloid Interface Sci. 197, 275). Satisfactory agreement was obtai ned between the experimental attachment efficiencies obtained in this study and those calculated with the Dobby-Finch model. In the attachment efficie ncy calculations, the induction time (t(ind)) varied with particle size (d( p)) according to the well-known equation, t(ind) = Ad(p)(B). The parameter B, with a value of 0.6, was found to be independent of particle size, parti cle contact angle, bubble size, and KCl electrolyte concentration. Converse ly, the value of the parameter A was dependent on the particle contact angl e, especially for contact angles smaller than 50 degrees, and on the bubble size but to a lesser extent on the electrolyte concentration. The value of A decreased with an increase in particle contact angle and an increase in bubble size. The values of the induction time obtained in this study are in a reasonable agreement with experimental and calculated induction times re ported in the literature. (C) 1999 Academic Press.