Flocculation as well as dispersion of mineral suspensions has become increasingly important in mineral processing as we
have to deal with fine and ultrafine particles. Population balance models for flocculation of such suspensions are discussed in
this paper. Models ranging from those based on pure aggregation and fragmentation to those based on simultaneous
aggregation–fragmentation are presented in detail. The two important parameters in the population balance model are the
collision frequency factor and the collision efficiency factor. Differences among collision frequency models for impermeable
and permeable aggregates are described. The main drawback of existing flocculation models is the disregard of forces between
mineral particle surfaces. The collision efficiency is usually assumed to be unity or employed as a fitting parameter in a majority
of the models. An approach for incorporating the influence of surface forces in the presence of salts and polymers is outlined.
Another important lacuna of flocculation models is the assumption of homogeneous flow structure or uniform fluid velocity
gradient in stirred flocculation tanks. Short-cut procedures adopted in the literature to address heterogeneous fluid flow structure
are summarized. It is also stressed that an integrated approach be followed to tackle practically relevant issues such as selective
flocculation of mineral mixtures, dual polymer flocculation, dynamics of polymer/surfactant adsorption, polymer–surfactant
interactions, surface precipitation of dissolved species and presence of air bubbles in the suspension.
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