Lyophilic colloids coagulation

Dr. Zelenev s professional interests include industrial applications of colloid and surface science, pulp and paper, oil and gas production, coagulation and flocculation, lyophobic and lyophilic colloidal systems, surfactant phase behavior, interaction of surfactants with surfaces, microencapsulation, particle deposition and aggregation, particle and surfactant transport in porous media, wetting and spreading, development of novel experimental methods for studying colloidal systems, and physical-chemical mechanics. Dr. Zelenev is an inventor on four issued U.S. patents and five pending patent applications, coauthor of 22 scientific publications, and coauthor of the textbook Colloid and Surface Chemistry (Elsevier, 2001). 

When discussing the factor of the strong stabilization of a thin film, we have primarily focused on a nonthermodynamic factor, that is, the mechanical resistance to media displacement and the mechanical stability of film against coalescence. Now, we will address the subject of colloid stability against coagulation, which is due to the competition between particle adhesion and particle involvement in thermal motion. If the latter prevails, the system can be characterized as lyophilic or is said to be lyophihzed. 

FIGURE 4.45 The free energy of interaction F (i.e., AOf) and the colloid stability (represented by the change in turbidity) in comparable macroscopic and nanoscopic systems lyophilized by a gradual increase of the water content. The addition of electrolyte promotes coagulation (transition from curve 1 to curve 3) hut does not have any significant impact on the value of F. (From Shchukin, E.D. and Yaminskiy, V.V., Colloids Surf., 32, 19, 1985.)... 

The presence of an essentially similar liquid medium and of surfactant adsorption influences the magnitude and nature of the surface forces and may result in weakened cohesion in the contacts by two to three orders of magnitude. In a lyophilized, highly concentrated system in which the particles are brought into mechanical contact, this is revealed through lower resistance to deformation, x, and results in a plasticizing of the system (see Chapters 2 and 3). When the disperse phase concentration is low, lyophilization leads to the preservation of the colloidal stability of a free-disperse system, that is, the resistance of the system to coagulation (see Chapter 4). 

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