floc

Floc is a term used in chemistry and environmental science to describe a mass of particles that have coagulated and agglomerated into a loosely connected cluster, or floc. In suspension, fine particles such as clays, organic matter, or microorganisms are often stabilized by electrical charges or steric hindrance. Floc formation reduces stability and promotes sedimentation or filtration.

In colloidal chemistry, flocs form when destabilized colloids contact and stick together, often aided by flocculants such as polymers or by changes in pH or ionic strength. The resulting floc is typically porous and may break apart under stress if weakly bound, and can coalesce into larger flocs through secondary flocculation.

In water and wastewater treatment, coagulation and flocculation are preparatory steps to remove suspended solids. Coagulants neutralize surface charges; flocculants bridge particles into larger flocs that settle in sedimentation basins or are removed by filtration.

In soil science, flocculation describes the aggregation of clay particles into larger units called flocs or microaggregates. This affects soil structure, porosity, water infiltration, and erosion resistance. Factors include clay mineralogy, organic matter content, electrolyte concentration, cation bridging (such as calcium or sodium), and soil pH.

The term is used more broadly to refer to any clumped mass formed by aggregation in colloidal systems. The plural form is flocs. See also flocculation, coagulation, and sedimentation.