Flockulation

Flockulation is the process by which dispersed particles, cells, or colloids in suspension aggregate to form larger, loosely bound clusters called flocs. In many contexts, the term is used as a synonym for flocculation, though some authors reserve flockulation for microbial or bio-aggregate formation in natural or engineered systems.

Mechanisms include neutralization of surface charge followed by attractive forces, bridging by polymeric flocculants, and depletion attraction caused by nonadsorbing polymers. Hydrophobic interactions and brief multivalent interactions can also promote aggregation. The resulting flocs are typically porous and fractal, with settling rates governed by size, density, and the strength of interparticle bonds.

Factors influencing flockulation include pH, ionic strength, temperature, and the presence of surfactants or natural organic matter; particle size and shape; and hydrodynamic conditions such as shear and mixing intensity. Flocs may be stable under certain conditions but can be disrupted by excessive shear or dilution.

Applications span water and wastewater treatment, where flockulation facilitates clarification and sedimentation; mining and mineral processing, for handling fine ores; the paper and pulp industry; and food processing. In aquaculture and environmental biotechnology, biofloc technology relies on microbial flocs to retain biomass and recycle nutrients.

Terminology notes: while widespread in colloid science, flockulation is less common than flocculation and can vary in meaning between disciplines. Related concepts include coagulation, sedimentation, and biofloc formation.