Colloid flocculation

Heil D, Sposito G. Organic-matter role in illitic soil colloids flocculation. II. Surface charge. J. Soil Sci. Soc. Am. 1993 57 1246-1253. 

Figure 8.8. Schematic illustrating the analogy between colloid flocculation behavior and phase behavior of the stabilizer in bulk solution. As density is lowered, separation of solvent from chains in bulk solution resembles separation of solvent from chains on surfaces, which produces flocculation.

In addition to the components given above (v0> v> C0) controlling colloidal flocculation or stability (stability is defined as the state or the conditions under which primary colloids are maintained) (Schofield and Samson, 1954 Shainberg and Letey,... 

The U.S. Soil Salinity Laboratory Staff (1954) reported that SAR values of 10-15 (mmol L )1/2 usually correspond to ESP values in the range of 10-15 at which values clays will undergo dispersion. This relationship may vary among colloids with different mineralogy (Oster et al., 1980) and/or mixtures of colloids with different mineralogy (Arora and Coleman, 1979). Consequently, the force by which given types of colloidal particles attract or repulse each other in a Na-Ca or Na-Mg solution is a function of the total concentration of the salt, the type of divalent cation (Ca or Mg), and SAR. Therefore, pH, salt concentration, type of divalent cation, and SAR are expected to play important roles on soil colloid flocculation. 

If you need to decrease the double-layer thickness by half in order to induce colloid flocculation, calculate the change in salt concentration you would need to introduce. Explain whether this is a realistic approach for cleaning up water. 

How is the zeta potential related to the two colloid flocculation approaches discussed in the answer to question 6 ... 

How do potential determining ions affect colloid flocculation or dispersion ... 

What is the practical importance of colloid flocculation-dispersion in nature ... 

Many processes in soil are controlled by colloid flocculation or dispersion. One such process is hydraulic conductivity. The data in Figure 10.3 show that for a Mg2+-saturated soil containing a solution of 3.16 x 10 2 M MgCl2, its hydraulic conductivity decreased by 35% after 5 hr of leaching with distilled water (Quirk and Schofield, 1955). This demonstrates that as solution ionic strength approaches zero, soil hydraulic conductivity decreases significantly owing to soil dispersion induced by a decompressed electric double layer. 

Crees, O. L. Senogles, E. Jones, Richard F. An Improved Demonstration of Colloid Flocculation, J. Chem. Educ. 1986, 63,715-716. 

Zwift and Friedlander [61] and Lushnikov [62] using Smoluchowski s kinetic equation [63] made the analysis of the time evolution of the mass frequency for colloids flocculating in a regime of fast aggregation by... 

The calcium cation produces many relatively insoluble salts. The most insoluble is calcium oxalate. Oxalic acid is used to demonstrate the presence of calcium in a liquid as it causes turbidity and precipitation. Calcium tartrate is also relatively insoluble, especially in the presence of ethanol (Section 1.6.5). In the same way, calcium gluconate and mucate, present in wine made from botrytized grapes, are reputed to be responsible for crystalline turbidity (Section 1.2.2). Calcium concentrations in white wines are between 80 and 140 mg/1, while they are slightly lower in red wines. The calcium content may increase following deacidification with calcium carbonate. As calcium is divalent, it is more energetically involved than potassium in colloid flocculation and precipitation, e.g. ferric phosphate, tannin-gelatin complexes, etc. 

Gum arable is also at least partially effective as a treatment for ferric casse in red wines. It does not prevent the appearance of a dark, blnish color, due to the formation of colloidal ferric tannate, but it does stop the colloid flocculating. It acts differently from citric acid, which prevents color from changing, as it produces a soluble complex with iron that is no longer capable of reacting with tannins (Section 4.6.2). These two treatments are often complementary (Section 4.6.3). 

Stress development. Generally, solidification is accompanied by development of in-plane tensile elastic stress. This is because departure of solvent from solution, crystallization and vitrification, consolidation of particulates, colloidal flocculation and coagulation, and the chemical reactions of curing almost always tend to produce shrinkage of the... 

Because of their amphoteric properties, animal glues possess electrical charges which unmodified or with suitable modification by simple chemical additives are highly effective as colloidal flocculents and as protective colloids in such applications as paper manufacturer, rubber compounding, ore and metal refining, and for water and industrial waste-water treatment. 

With decreasing equivalent weight of the colloid flocculability increases, in so far as flocculation or coacervation is already realisable with lower valent cations the lower the equivalent weight (see however also p. 295, 2 m),... 

In lyophobic colloidal systems, the addition of sufficient salt generally brings about flocculation. An analogy between colloidal flocculation and the nonbinding-binding transition has been drawn [48]. The counterion layer around the micelle is narrowed in a solution containing higher concentration of ions, which facilitates the approximation of the solute to the micellar assembly. Hydrophobic interactions between the solute and the nonpolar core of the micelle can then be established. 

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