Irreversible coagulation

Reversibility of coagulation Irreversible as a rule Reversible as a rule... 

Figure 4.6 Calculated energy profiles of DLVO interactions as a function of the distance between particle surfaces, (a) Surfaces repel strongly coUoidal particles remain stable, (b) Surfaces come into stable equilibrium if the secondary minimum is deep enough colloids then aggregate reversibly, (c) The interaction curve approaches the pure van der Waals curve and colloids coagulate irreversibly.

It is assumed that irreversible aggregation occurs on contact. The rate of coagulation is expressed as the aggregation flux J of particles towards a central particle. Using a steady-state approximation, the diffusive flux is derived to be... 

Coagulation a relatively irreversible aggregation often associated with the primary minimum of a potential energy diagram of two approaching particles. Particles are held together closely. 

Denaturation is accompanied by changes in both physical and biological properties. Solubility is drastically decreased, as occurs when egg white is cooked and the albumins unfold and coagulate. Most enzymes also lose all catalytic activity when denatured, since a precisely defined tertiary structure is required for their action. Although most denaturation is irreversible, some cases are known where spontaneous renaturation of an unfolded protein to its stable tertiary structure occurs. Renaturation is accompanied by a full recovery of biological activity. 

Porcelli D, Andersson PS, Baskaran M, Wasserburg GJ (2001) Transport of U- and Th-series nuclides in a Baltic Shield watershed and the Baltic Sea. Geochim Cosmochim Acta 65 2439-2459 Quigley MS, Santschi PH, Guo LD, Honeyman BD (2001) Sorption irreversibility and coagulation behavior of " Th with marine organic matter. Marine Chem 76 27-45 Rama MK, Goldberg ED (1961) Lead-210 in natural waters. Science 134 98-99... 

Analytical approaches to obtain the agglomerate size distribution are possible for well-mixed systems and when the rate of aggregation of clusters is defined by simple functions. In general, irreversible aggregation in well-mixed systems is described by Smoluchowski s coagulation equation, which... 

While the system conforms to coagulation in a secondary minimum, the redispersion region is best accounted for in terms of gel formation originating from the rod-like shape of the particles and hydrated surface. During the final coagulation process additional attractive forces such as dipolar and hydrogen bonding form floes which are irreversible and denser than those formed at a lower salt concentration. 

In the course of further work on characterizing the MCC sols it was found that the CCC of a variety of salts varied both with the solids content and temperature. Investigation of these parameters forms the basis of the study. It will be shown that as a result of particle shape, concentration and surface characteristics, coagulation leads to a gel-like structure. On further addition of salt the coagulated gel-like structure aggregates into floes that are irreversible. In this paper, we outline the experimental parameters which lead to these phenomena and present some possible explanations. 

Properties of Egg Albumen. Egg albumen is normally used in foods for two reasons it whips into a foam and the foam can be set irreversibly by heat. One advantage of egg albumen is that it is relatively unaffected by the presence of fat. Fat in these systems acts as a foam breaker. Some other whipping agents are badly affected by the presence of fat. In confectionery systems egg albumen is usually set by beating the reconstituted egg albumen into a hot sugar syrup. The coagulation... 

Coagulation The irreversible formation of the thermodynamically stable phase in bulk quantities The precipitation of crystals... 

Colloids are thermodynamically unstable conglomerates that form heterogeneous dispersions in aqueous systems. They tend to coagulate and precipitate, which means that the materials of which they are composed may be present both in the water column and in sediments. The coagulation and precipitation stages are generally considered irreversible, but forces in the environment can redisperse the particles. 

Denaturation is the irreversible precipitation of proteins caused by heating, such as the coagulation of egg white as an egg is cooked, or by addition of strong acids, bases, or other chemicals. This denaturation causes permanent changes in the overall structure of the protein and because of the ease with which proteins are denatured it makes it difficult to study natural protein structure. Nucleic acids also undergo denaturation. 

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