Natural flocculants

Figure 9.1 Example of typical grain-size spectra of suspended particulate matter from coastal waters with high inorganic content. The solid curves show the natural flocculated particle distributions and the broken curves show the deflocculated inorganic grains. From Yariv and Cross [49], Copyright 1979, Springer-Verlag Berlin.

Natural flocculants Starch, guar, and other natural materials have historically been used for sedimentation flocculation, but have been replaced by more effective synthetic polymers. 

Figure 378. Natural flocculation of solid contaminants in river water. Parameters are circumferential speed of the stirrer and processing time ...

The choice of reagent is empirical and may depend as much on financial considerations as technical ones. As an example, the process economics may decide whether a relatively inefficient natural flocculant such as starch is used rather than a more efficient, but also more expense polyacrylamide. If the feed stream to be treated is of very constant composition or if variables such as pH are not e q>ected to change it may be more effective to use a specific flocculant. On the other hand, if conditions are more variable, a less specific hut less efficient flocculant is probably better. 

Of the other types, amphoteric, structured and natural flocculants are perhaps the most important. In the former, the polymer molecules contain both cationic and anionic charge sites and/or functional groups. Although amphoteric polymers need to be manufactured under very carefully controlled conditions and little seems to be known about their modus operandi, there are claims for the improved flocculation of materials such... 

Iron may be concentrated in acid mine waters and naturally occurring groundwaters. Natural flocculents of iron(III) oxide occur when iron-rich groundwaters enter the surface environment and are rapidly oxidised. These can form relatively pure ochreous deposits in ephemeral lakes and waterways or form as either a scum or muds in wetland environments. Evidence for the use of this material as a pigment is documented in Scott et al. (2002). 

Novel Application of Natural Rubber Latex as Natural Flocculant for Tin Tailings Slurry... 

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