Particle size is an important parameter in flotation and has been the focus of flotation research for decades. The difficulty in floating fine particles is attributed to the low probability of bubble-particle collision. In this research, the influence of hydrodynamic parameters on collision probability of fine particles was investigated. Collision probability was obtained using Stokes, intermediate I and intermediate II and potential equations Maximum collision probability was 5 65% obtained with impeller speed of 1100 rpm, air flow rate of 301/h and particle size of 50 mu m. Also, attachment probability under Stokes flow, turbulent and potential flow conditions was calculated 100, 99 49 and 81 87% respectively Maximum attachment probability was obtained with impeller speed of 700 rpm, contact angle of 90 degrees, particle size of 20 mu m and air flow rate of 151/h. Collision angles were obtained between 60 71 degrees and 60.18 degrees and attachment angles were obtained between 9.15 degrees and 59 83 degrees. (C) 2010 Elsevier B V All rights reserved