Deijaguin-Landau-Verwey-Overbeek

Ruckenstein and Schiby derived4 an expression for the electrochemical potential, which accounted for the hydration of ions and their finite volume. The modified Poisson-Boltzmann equation thus obtained was used to calculate the force between charged surfaces immersed in an electrolyte. It was shown that at low separation distances and high surface charges, the modified equation predicts an additional repulsion in excess to the traditional double layer theory of Deijaguin—Landau—Verwey—Overbeek. 

According to Deijaguin-Landau-Verwey-Overbeek (DLVO) theory, a cornerstone of modem colloid science, two types of forces exist between colloidal particles suspended in a dielectric medium electrostatic forces, which result from an unscreened surface charge on the particle, and London-van der Waals attractive forces, which are universal in nature. The colloidal stability and rheology of oxide suspensions, in the absence of steric additives, can be largely understood by combining these two forces (assumption of additivity). 

At low concentrations of dissolved organic matter (DOM) (<0.01 mg of C/L) and at low ionic strength (10 3 M), the hematite particles are positively charged at this pH and are stabilized electrostatically by interacting diffuse layers with characteristic (Debye) lengths of 10 nm. As the ionic strength is increased to 10 1 M at these low DOM concentrations, the diffuse layers are compressed to 1 nm, and attractive van der Waals forces promote attachment in classical Deijaguin-Landau-Verwey-Overbeek (DLVO) destabilization by what has been termed double-layer compression. 

From the brief sketch of the Deijaguin, Landau, Verwey, Overbeek (DLVO)-theory the following three important practical conclusions, suitable for foams and emulsions, can be drawn ... 

TTHE MOST IMPORTANT FORCES ACTING BETWEEN MEMBRANE SURFACES are van der Waals, electrostatic, and hydration. The first two forces are explained by the Deijaguin-Landau-Verwey-Overbeek (DLVO) theory (I) the existence of the hydration force was anticipated before it was measured (2). The van der Waals force is always attractive and displays a power law distance dependence, whereas the electrostatic and hydration forces are repulsive and exponentially decay with distance. The electrostatic force describes the interaction between charged membrane surfaces when the separation between surfaces is above 10 molecular solvent diameters. The hydration force acts between charged and uncharged membrane surfaces and at distances below 10 molecular solvent diameters its value dominates the values of van der Waals and electrostatic forces (3). The term hydration reflects the belief that the force is due to the structure of water between the surfaces. Electrostatic and hydration forces are similar in some respects both are exponential and repulsive and their theoretical description involves coupling electrostatic concepts and ideas borrowed from statistical mechanics. Although the nature of the electrostatic force is solidly established, this is not the case for the hydration force. To illustrate the role the electrostatic... 

For example, it is well known that the silica hydrosols are stable at their point of zero charge (pzc) and that they also coagulate in alkaline solutions, in which their electrical smface charge is high and should therefore increase their stabUity. Such behavior is very unusual indeed, and this question arises immediately Why does the Deijaguin-Landau-Verwey-Overbeek (DLVO) theory seem to be unable to cope with the silica hydrosols while it explains satisfactorily, at least to the best of our knowledge, the behavior of all other colloidal systems ... 

Spitzer, J. J. 2003. Colloidal interactions Contact limiting laws, double-layer dissociation, and non-DLVO (Deijaguin-Landau-Verwey-Overbeek) forces. Colloid and Polymer Science 281, no. 6 589-592. doi 10.1007/s00396-002-0836-3. 

Fig. 1 Interactions between nanoparticles, (a) Traditional forces for colloidal stabilization (e.g., electrostatic, van der Waals, steric) that occur when particles are dispersed in aqueous media, (b) The van der Waals forces are attractive whereas the electrostatic forces are repulsive ovta- a typical length scale. The Deijaguin-Landau-Verwey-Overbeek theory in colloid science considers the sum of these forces. Reprinted with permission from [80]. Copyright 2011 EIscvIct...

Direct adhesion of particles to fibres can be explained with Deijaguin—Landau— Verwey—Overbeek (DLVO)" " theory for soft cell particles,and the adhesion of cell particles to the fibres may be quantified by using the attachment rate coefficient, att which is related to the collision efficiency, rj, and the sticking efficiency, , as follows... 

Having reviewed the properties of single adsorption monolayers, we proceed with the couples of interacting monolayers the thin liquid films. First, we present the thermodynamics of thin films, and then we describe the molecular theory of the surface forces acting in the thin films. We do not restrict ourselves to the conventional DLVO (Deijaguin, Landau, Verwey, Overbeek) forces [2,3], but consider also the variety of the more recently discovered non-DLVO surface forces [4]. The importance of the micelle-micelle interaction for the mechanism of micelle growth is also discussed. 

This is the well-known empirical Schulze-Hardy rule of coagulation concentration, which has been confirmed experimentally in many colloidal systems. The above theory of dispersion and coagulation of colloidal particles, based on the repulsive interaction between two diffuse layers and on the attractive interaction owing to the van der Waals-London force, is called the Deijaguin-Landau-Verwey-Overbeek (D.L.V.O.) theory. 

The stability of colloidal dispersions is often described quantitatively via the DLVO (Deijaguin-Landau-Verwey-Overbeek) theory which accounts in a simple additive way for both the (usually) attractive van der Waals (vdW) energies, V,, and the (typically) repulsive electric/electrostatic or double-layer energies, Vr ... 

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