Flocculation coagulation kinetics

In summary, polymeric flocculants generally increase peri-kinetic flocculation rates compared with perikinetic coagulation rates. This is not necessarily true for orthokinetic flocculation, and experimental results in the literature are seemingly in conflict. Collision rate theory predicts that the polymer adsorption step may become rate limiting in orthokinetic flocculation. The present study was designed to elucidate the relationship between polymer adsorption rates and particle flocculation rates under orthokinetic conditions. 

Similarly, a weak repulsive steric interaction in combination with a strong van der Waals interaction will result in flocculation. The kinetics of coagulation and flocculation in the presence of a total interaction energy profile either electrostatic or steric is discussed next. 

Alkylpyridinium or ammonium halides constitute a group of cationic detergents with well known surface properties. The kinetics of emulsion breaking or in general coagulation, comprises flocculation and coalscence. It has been reported (1) that cations and anions at low concentrations retard the coalescence and association of dispersed phase of emulsions. 

The emulgent, phthallylsulfathiazole provides highly stable type of emulsions. Even in the presence of cationic surfactants, these emulsions were found to be reasonable stable. Effect of detergents on the stability was in the order CPB < CPC < CTAB < LPC, which is compatible with their chain length. The rate determining step of coagulation kinetics of the system under investigation is the coalescence as this is slower than flocculation. 

It is now well established that most colloidal systems in aqueous media remain stable because of the cooperative effect between electric charges attached to the suspended particles and the counter-ions in the immediate environment around them. A suitable description of this electrical picture,therefore, must be included in the foundation for any thermodynamic or statistical mechanical analysis of such colloidal systems. One should also point out,however, that many problems of practical interest are concerned with irreversible processes taking place in the colloid, i.e. coagulation or flocculation, rheology, and electro-kinetic behavior. An understanding of these processes cannot be derived from equilibrium phenomena. Moreover, even a complete treatment of colloid equilibrium should not be based exclusively on electrostatic considerations but should also allow for short range forces, such as van der Waals attraction. 

There are two general theories of the stabUity of lyophobic coUoids, or, more precisely, two general mechanisms controlling the dispersion and flocculation of these coUoids. Both theories regard adsorption of dissolved species as a key process in stabilization. However, one theory is based on a consideration of ionic forces near the interface, whereas the other is based on steric forces. The two theories complement each other and are in no sense contradictory. In some systems, one mechanism may be predominant, and in others both mechanisms may operate simultaneously. The fundamental kinetic considerations common to both theories are based on Smoluchowski s classical theory of the coagulation of coUoids. 

Tphe kinetics of the protease-triggered clotting of blood and milk has been formulated in a number of recent publications from this laboratory (1,2,3). In milk clotting, the coagulation is initiated through the limited proteolysis of -casein, the milk protein component which normally protects the casein micelles from flocculation by calcium ions (4). Kappa-casein is a single polypeptide chain of 169 residues, the sequence... 

Doublet formation is the first step of aggregate or cluster formation. When salt or pH is used to destabilize a colloidal suspension it is referred to as coagulation. When a polymer or surfactant is used to destabilize a colloidal suspension it is referred to as flocculation. The kinetics of doublet formation for both these methods of destabilizing a colloidal suspension is discussed in this section. 

Chen, W. J., D. P. Lin, and 1. P. Hsu (1998). Contrihution of electrostatic interaction to the dynamic stability coefficient for coagulation-flocculation kinetics of beta-iron oxy-hydroxides in polyelectrolyte solutions. J. Chem. Eng. Japan. 31, 5, 722-733. 

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