Colloids types

Colloids are introduced in the second half of the chapter. The various classifications of colloid types are discussed, together with ways of forming, sustaining and destroying colloids, i.e. colloid stability. Finally, association colloids ( micelles ) are discussed. 

COLLOID TYPE SUBSTANCE DISPERSED DISPERSING MEDIUM EXAMPLES... 

A major outcome of the abovementioned studies is the importance of pH and notably of the salinity of the groundwater controlling colloid concentrations and, consequently, the relevance of colloids for radionuclide transport. The pH-dependent colloid stability varies considerably for different colloid types. Experimental data for the relationship of the stability ratio W... 

Examples Dispersing Medium Dispersed Substance Colloid Type... 

Two types of colloids are recognized in the literature. Intrinsic colloids (also called true colloids, type I colloids, precipitation colloids, or Eigencolloids ) consist of radioelements with very low solubility limits. Carrier colloids (also known as pseudocolloids, type II colloids or EremdkoIIoides ) consist of mineral or organic phases (in natural waters primarily organic complexes, silicates and oxides) to which radionuclides are sorbed. Both sparingly soluble and very soluble radionuclides can be associated with this type of colloid. In addition, radionuclides can be associated with microbial cells and be transported as biocolloids. 

On treating an aqueous solution containing 01% gold chloride or 0-05% palladium chloride with dichloroethyl sulphide a turbidity of colloidal type quickly forms, and if the quantity of the sulphide is large, yellowish-red oily droplets are produced. 

For example, Soga et al. > found, by examining propylene polymerization in toluene in the temperature range 0-65 °C with an apparently soluble catalyst such as tetrabenzylzirconium, that the isotactic index and the polydispersity of the polymer increased as the polymerization temperature increased. Furthermore, the value of Q > 30 was much greater than that predicted for homogeneous active centres. From these results the authors concluded that the catalyst should be made up of small invisible colloid-type particles. The same interpretation is valid for the surprising results (Q 40) obtainedfor polyethylene, in Isopar solution at 200 °C, with the originally soluble tetrabenzylzirconium-water catalyst. 

The suspended solids in the composite wastewater samples from the detergent and soap factory were a fine divided colloidal type which require a very long detention time to achieve not more than 10% removal ratio. On this basis the primary sedimentation unit of the conventional activated sludge system was eliminated. 

Colloid-Type Systems. The evidence available in the literature appears to indicate that the hydrocarbon structures and some features, such as the various condensed ring systems, in different crude oils are similar. The variety of source materials involved in petroleum genesis, however, implies that, on an individual molecular scale, there may be substantial structural differences among the constituents of crude oil and bitumen. 

Phase of Colloid Dispersing (solvem-like) Substance Dispersed (solute-like) Substance Colloid Type Example... 

Eight different asphalt samples belonging to three different colloidal types were used in this study. Asphaltene sample that were used in the TEM metal shadowing were isolated by... 

Concentrating in the value of size distribution of Table HI and Figure 2, it easy to determine that samples AAM-1 and AAG-1 are in the same group samples AAA-1, AAQ-1, and AAD-1 are in another group and Samples AAE-1, ABA-1, and AAK-1 are different from the previous two groups. The values of size distribution for these three groups are around 1.90, 1.51, and 1.39, respectively. These three groups appear to represent three different colloidal types of asphalts, sol, sol-gel, and gel type, respectively. 

Figure 2 Plot of size distribution vs. irregularity for eight asphalt samples. The three colloidal types of asphalt are indicated in the graph.

We obtained solubility parameter spectra of asphalt and asphaltenes for three different colloidal types of asphalt (AAM-1, AAA-1, and ABA-1). Figures 4-6 represent the solubility parameter spectra for asphalt, and Figures 7-9 represent that for asphaltenes. Comparing the solubility parameter of asphalt and asphaltenes, it can be found that the solubility parameters of asphalt and asphaltenes are around 7-10.5 and 8.5-10, respectively. Without a doubt, the composition of asphalt is more complex than that of asphaltenes. Therefore, the solubility parameter of asphalt has a wider range than that of asphaltenes. 

The examples of colloids listed in Table 10.2 may be considered simple colloids because they involve one fairly distinct type of dispersed and continuous phase. In practice, many colloidal systems are much more complex in that they contain a variety of colloidal types, such as a sol, an emulsion (or multiple emulsions), an association colloid, macromolecular species, plus the continuous phase. Such systems are often referred to as complex or multiple colloids. As we shall see, even the simplest colloids can be quite complex in their characteristics. It should be easy to understand, then, why the difficulty of understanding a multiple colloid increases dramatically with the number of components present. 

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