Shear flocculation - kinetics of floc coalescence and breakage

The flocculation of ultrafine (size < 10 m) hydrophobic particles in the presence of a high shear field is known as shear flocculation. Most of the studies carried out to date are related to surface chemistry of the process. However, study of the shear flocculation process using mathematical models is quite limited. The present study uses a lumped population balance model (PBM) to understand the effect of different parameters affecting the kinetics of flee coalescence and breakage processes in shear flocculation. Results show that the flocculation rate decreases with increase in shear rate and the breakage rate is approximately proportional to the 0.70 power of the volume of the floc. High concentrations of sodium oleate reduce the flee strength. Modifiers like sodium carbonate and sodium silicate decrease the flocculation rate. (C) 2001 Elsevier Science B.V. All rights reserved.