Flocculation

Flocculation 

a form of coagulation in which fine particles suspended in a liquid or gas form loose, fluffy clusters called floes. In disperse liquid systems, such as sols, suspensions, emulsions, and latexes, flocculation occurs through thermal, mechanical, or electrical means. Soluble polymers, particularly polyelectrolytes, are effective flocculants.

The action of polymeric flocculants is usually explained as the simultaneous adsorption of long-chain macromolecules on several particles. The clusters that develop form flakes that can be easily removed by settling or filtering. Flocculants, for example, polysilicic acid or polyacrylamide, are widely used in treating water for industrial or domestic needs. They are also used in mineral concentration, in the pulp and paper industry, in agriculture (for improving soil structure), in the separation of valuable products from industrial wastes, and in the decontamination of industrial sewage. In water purification, polymeric flocculants are usually used in concentrations of 0.1–5 mg/liter. Flocculation by the organic substances present in bodies of water in nature is an important factor in the self-purification of such waters.

REFERENCES

Kul’skii, L. A. Teoreticheskie osnovy i tekhnologiia konditsionirovaniia vody, 2nd ed. Kiev, 1971. Page 138.
Voiutskii, S. S. Kurs kolloidnoi khimii, 2nd ed. Moscow, 1975.
Veitser, Iu. I., and D. M. Mints. Vysokomolekuliarnye flokulianty v protsessakh ochistki vody. Moscow, 1975.

L. A. SHITS