Chairoj Rattanakawin

pp. 477 - 483

Abstract

The evolution of aggregate (floc) size distributions resulting from hydrophobic flocculation has been
investigated using a laser light scattering technique. By measuring floc size distributions it is possible to
distinguish clearly among floc formation, growth and breakage. Hydrophobic flocculation of hematite suspensions with sodium oleate under a variety of agitating conditions produces uni-modal size distributions.
The size distribution of the primary particles is shifted to larger floc sizes when the dispersed suspension is
coagulated by pH adjustment. By adding sodium oleate to the pre-coagulated suspension, the distribution
progresses further to the larger size. However, prolonged agitation degrades the formed flocs, regressing the
distribution to the smaller size. Median floc size derived from the distribution is also used as performance
criterion. The median floc size increases rapidly at the initial stage of the flocculation, and decreases with the
extended agitation time and intensity. Relatively weak flocs are produced which may be due to the low dosage
of sodium oleate used in this flocculation study. It is suggested that further investigation should focus on
optimum reagent dosage and non-polar oil addition to strengthen these weak flocs.

Keywords

• aggregate size distribution
• hydrophobic flocculation