A critical review of the various models existing in the literature for the
calculation of the collision efficiency between particles and single, risin
g gas bubbles is presented. Although all of these collision models predict
that the collision efficiency increases with particle size, their dependenc
e on the latter is different because of the various assumptions and hydrody
namic conditions used in each model. Collision efficiencies of quartz parti
cles with single bubbles have been obtained from experimental flotation exp
eriments under conditions where the attachment and stability efficiencies w
ere at, or near, unity. These collision efficiencies were then used to test
various collision models. Good agreement between the experimental and calc
ulated collision efficiencies was only obtained with the Generalised Suther
land Equation. The differences in collision efficiencies obtained between t
he various models were mainly explained in terms of, firstly, the degree of
mobility of the bubble surface and, secondly, a consideration of the inert
ial forces acting on the particles. (C) 2000 Elsevier Science B.V. All righ
ts reserved.