The density of particle aggregates

Aggregates of particles formed in coagulation/flocculation processes very often have a fractal, self-similar structure, with the very important practical consequence that the effective density of aggregates decreases as their size increases. This has very significant effects on separation processes such as sedimentation, flotation and filtration. The fundamental factors which influence the density of aggregates (flocs) are reviewed, with a discussion of the effects on aggregate size distribution, the rate of formation of flocs and their capture by collectors. Several experimental methods for determining floc density are critically examined.