Fines attractive energy between

Volume of solution or mixture, also particles, column, and porous medium London attractive energy between two molecules or particles Coarse particle volume Fine particle volume Carrier liquid volume London attractive energy per unit area between two infinite flat plates London attractive energy between two identical spheres Elution volume, Eq. (4.7.3)... 

The attractive interaction depends largely on the Hamaker constant A, as shown in Eq. (2). The larger the value of A, the greater is the attractive energy between the particles. The net interaction energy is then the sum of Vr and Va-Equations (1) and (2) show that a better dispersion of fine particles must come from systems having large tj/rf and small A. 

The most widely used theory of suspension stability, the DLVO theory, was developed in the 1940s by Derjaguin and landau (1941) in Russia and by Verwey and Overbeek (1948) in Holland. According to this theory, the stability of a suspension of fine particles depends upon the total energy of interaction, Vt, between the particles. Vf has two components, the repulsive, electrostatic potential energy, Vr, and the attractive force, Va, i. e. 

Attractive Forces. Attractive forces, collectively called van der Waal s forces, exist between two oil droplets. Simplistically, these forces may be thought of as the attraction between oil molecules at the o/w interfaces that have lower energy when in contact with each other than when in contact with water. Several phenomena are involved hydrophobic interactions and London dispersion forces are most commonly considered. These are effective as (roughly) the fourth power of the distance between the surfaces and are unaffected by ionic strength. The attraction due to van der Waal s forces is shown in Figure 6. Suspensions of solids (cellulose fibers, finely divided CaCOa, etc.) are stabilized in the same way. Ionic surfactants are used that selectively adsorb to the solid surface, generating a v[/ potential and making possible a stable suspension. 

Depletion interactions are interactions between two surfaces (particles) in the presence of firee, i.e., non-adsorbed, macromolecules, micelles, or very fine particles. Asakura and Oosawa (1954) first pointed out that if the distance between two surfaces h is smaller than the diameter of solute molecules Jm, this region will contain pure solvent depletion zone, cf. Fig. 3.14, left). Thus, an attractive force corresponding to the osmotic pressure of the bulk solution is acting on the two surfaces. Agglomeration caused by this effect is called depletion flocculation. In a second paper, the authors calculated the potential energy of this interaction for... 

Cohesiveness and adhesion Cohesiveness of a powder is the ability of individual particles to stick together. This attraction may be caused by the presence of moisture, electrostatic charges or the fineness of the particles within a powder. Fine powders generally have a high surface area, which is usually associated with an increase in the surface energies within the powder and thus enhancement of the binding forces between particles (Stanley Wood et al. 1990). 

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