Destabilization of Colloids

one needs to be aware that simply adding polymers and polyelectrolytes to a dispersion does not ensure protective action. In fact, the opposite can happen, especially if the added concentration is very low or if the polymers can form bridges across multiple dispersed species. 

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Our model predicts destabilization of colloidal dispersions at low polymer concentration and restabilisation in (very) concentrated polymer solutions. This restabilisation is not a kinetic effect, but is governed by equilibrium thermodynamics, the dispersed phase being the situation of lowest free energy at high polymer concentration. Restabilisation is a consequence of the fact that the depletion thickness is, in concentrated polymer solutions, (much) lower than the radius of gyration, leading to a weaker attraction. 

A small fraction of POM is created via abiotic processes, all of which involve transformation of DOM into the particulate phase. As already noted, destabilization of colloidal DOM can lead to the formation of gels. Increasing salinity destabilizes colloids, so flocculation of DOM is common in estuaries. 

Another source of attraction between two surfaces is possible when the surfaces are immersed in a solution of a nonadsorbing polymer (e.g., a polymer that does not adsorb on, or is repelled by, the surfaces). Although this force is generally weak, it can play a significant role in destabilization of colloidal particles under certain circumstances. 

The Role of Adsorption in the Destabilization of Colloidal Dispersions by Hydrolyzed Al(III)... 

It is well known that hydrolyzed polyvalent metal ions are more efficient than unhydrolyzed ions in the destabilization of colloidal dispersions. Monomeric hydrolysis species undergo condensation reactions under certain conditions, which lead to the formation of multi- or polynuclear hydroxo complexes. These reactions take place especially in solutions that are oversaturated with respect to the solubility limit of the metal hydroxide. The observed multimeric hydroxo complexes or isopolycations are assumed to be soluble kinetic intermediates in the transition that oversaturated solutions undergo in the course of precipitation of hydrous metal oxides. Previous work by Matijevic, Janauer, and Kerker (7) Fuerstenau, Somasundaran, and Fuerstenau (I) and O Melia and Stumm (12) has shown that isopolycations adsorb at interfaces. Furthermore, it has been observed that species, adsorbed at the surface, destabilize colloidal suspensions at much lower concentrations than ions that are not specifically adsorbed. Ottewill and Watanabe (13) and Somasundaran, Healy, and Fuerstenau (16) have shown that the theory of the diffuse double layer explains the destabilization of dispersions by small concentrations of surfactant ions that have a charge opposite to... 

FIGURE 12.4 Reduction of zeta potential to canse destabilization of colloids. 

The destabilization of colloids through the addition of counterions should be done in conjunction with the application of the complete coagulation process. Four methods are used to bring about this process double-layer compression, charge neutralization, entrapment in a precipitate, and intraparticle bridging. 

As is evident from equations 11 and 12, the efficiency of filtration can be improved by improving the attachment of the particles to the filter grains. The considerations applied to the destabilization of colloids can also be used in filtration. A practical example is given in Figure 14.24 for phosphate elimination in sewage treatment. 

In this chapter, the theories as well as the experimental justification for the mechanism of stabilization and destabilization of colloidal dispersions are outlined. Interacting forces between colloidal particles are analyzed and an overview of experimental methods for assessing the dispersion and relevant properties is given. The stabilization and flocculation of dispersions in the presence of surfactants and polymers is discussed in the last two sections. 

Finally, vitreous silica can be manufactured by the sol-gel technique developed by Zarzycki [39], Gels are formed by the destabilization of colloidal sols or by the hydrolysis of metal organic compounds. This latter routine is the most common technique that yields a silica-alcohol-water gel. Subsequently, the gel is dried and fused to produce silica glass. The manufacture of 3D articles by this method is limited due... 

Chemical coagulation Destabilization of colloidal and suspended matter by the reduction of... 

Interactions manifest themselves in the irreversible and incomplete destabilization of colloids in inefficiently mixed systems or in the heterodispersity of sols formed under conditions of non-homogeneous energy dissipation or through the differing effectivity of liquid-solid-separation for coagulated systems. 

Gelation can be produced by destabilization of colloidal silica sols wherein the colloidal size can range between 1 and 1000 run. Alternatively, polymeric gels can be produced by the hydrolysis of metal-oiganic compounds in solution. 

Adding polymers can result in both stabilization and destabilization of colloidal systems (Figure 12.12). 

Intermolecular and surface forces embrace all forms of matter. Understanding their nature is of great scientific interest and relevant for a wide range of applications. These include stabilization (or destabilization) of colloids, design of molecular sensors, modification of liquid flow in narrow gaps, slow release and dmg delivery, adhesion, friction, and lubrication. - "... 

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