Flocculation


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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

References in periodicals archive ?
Contrarily, the disproportionate dosage led to a sort of cake effect and electrostatic repulsion which stopped the floc growth and reduced the flocculation efficiency.
Electrostatic interactions, charge neutralization and bridging are among the major interactions involved in dye adsorption and coagulation flocculation. Natural polymers are long chain molecules with free charge bearing ends.
Yang et al., "Chromium (VI) detoxification by oxidation and flocculation of exopolysaccharides from Arthrobacter sp.
3) reveal a comparison of COD removal in coagulation and flocculation (65%), in oxidation (87.9%) and in RO (99.8%).
Based on previous discussions, it can be concluded that the yield stress of MRF is depended on the structural strength of flocculation structures formed during magnetic agglomeration.
By contrast, free radical copolymerization has been proven to be a convenient and effective approach, which integrates specific functional groups of monomers while simultaneously generating some new features for improvement of flocculation ability [20-22].
The efficiency of the flocculation was evaluated using the following equation proposed by Zuharlida et al.
This is to extend the results of pure montmorillonite-PAM or kaolinite-PAM interactions to whole soils with similar clay minerals and to compare the differences in clay flocculation behaviours in response to PAM addition in the two distinct systems.
Flocculation is a common separation improvement technique to improve water recycle and control fines accumulations.
Sand filtration is not a safe method for recovering Ti[O.sub.2] nanoparticles, because only under conditions leading to Ti[O.sub.2] agglomeration (pH 7), retention of photocatalyst particles in a sand filter was observed, while at pH 5 flocculation and also retention of particles were low [6].