Coagulation and Flocculation

Flotation is certainly the major separation method based on the surface chemistry of mineral particles. It is, however, not the only method. Selective flocculation and agglomeration may be mentioned as other methods used commercially to a limited extent. The former is for hematite, while the latter is for coal and finely divided metallic oxide minerals. Both processes use the same principles as described for flotation to obtain selectivity. In selective flocculation, polymeric flocculants are used. The flocculants selectively adsorb on the hematite, and the hematite floes form and settle readily. Thereby separation from the sili- 

Floes possess two important settling features. The first is their complicated structure. The aggregates are lax, the interparticle bond in them is weak, and they hold a large amount of water in their structures, which is retained with the floes when they settle. The second feature of the flocculated pulp is the complexity of its settling mechanism. 

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Explain the terms coagulation and flocculation. How do you envision these operations are practiced ... 

Coagulation and Flocculation Theory and Applications, edited by Bohuslav Dobias... 

There is a very wide range of coagulant and flocculant polymers. 

There are a number of major, international manufacturers of coagulant and flocculant polymers whose primary markets are high-volume users (i.e., cities, states, and national governments). There are also many smaller regional manufacturers who tend to specialize in niche markets and produce various polymer blends (organic polymers blended with various ratios of inorganic coagulants such as ACH, PAC, and alum). These polymer blends are particularly useful in industrial facilities where process contamination and difficult clarification problems may exist. 

With lower heat-flux ratings and higher ratios of internal water volume to heating surface than is the norm today, complex external treatment was not always necessary where deemed necessary, it was often limited to basic sedimentaion or filtration techniques employing inorganic coagulants and flocculants, typically followed by the use of natural zeolites (see sections 9.2.3.1 and 9.2.5 for additional information). 

Defoaming Theory and Industrial Applications, edited by P. R. Garrett Mixed Surfactant Systems, edited by Keizo Ogino and Masahiko Abe Coagulation and Flocculation Theory and Applications, edited by Bohusiav DobiaD Biosurfactants Production Properties Applications, edited by Naim Kosaric Wettability, edited by John C. Berg... 

Method Chemical precipitation of dissolved and complexed metals by reaction with lime and subsequent removal of the precipitated solids by gravity settling in a clarifier. Alum and polyelectrolyte are added for coagulation and flocculation. 

The polymer radius has to be larger than 80% of the particle radius to avoid adsorption limitation under orthokinetic conditions. As a rule of thumb a particle diameter of about 1 pm marks the transition between perikinetic and orthokinetic coagulation (and flocculation). The effective size of a polymeric flocculant must clearly be very large to avoid adsorption limitation. However, if the polymer is sufficiently small, the Brownian diffusion rate may be fast enough to prevent adsorption limitation. For example, if the particle radius is 0.535 pm and the shear rate is 1800 s-, then tAp due to Brownian motion will be shorter than t 0 for r < 0.001, i.e., for a polymer with a... 

Water treatment, 26 102-152. See also Aeration water treatment, Industrial water treatment ABS manufacture, 7 421-422 activated carbon application, 4 752 aerators, 26 158-170 alkanolamines from nitro alcohols, 2 120 coagulation and flocculation in,... 

Some authors distinguish between coagulation and flocculation and use the latter term for colloid agglomeration by bridging of polymer chains. 

O Melia, C. R. (1972), "Coagulation and Flocculation", in W. J. Weber Jr., Ed., Processes for Water Quality Control, John Wiley and Sons, New York, 61-110. 

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