Derjaguin-Landau- Verwey-Overbeek DLVO theory

Application of DLVO Theory. Some of the concepts and expressions of Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory of colloid stabihty have been described in Chapter 1, or can be found in many different textbooks 4, 5). The application of DLVO theory to oil-in-water colloids with special reference to the stability of bitumen-in-water emulsions will be discussed here. 

Two approaching emulsion droplets may be resisted by electrostatic forces. Electrostatic forces consist of Coulombic repulsion between two like charged objects and attractive van der Waals forces. These two forces are accounted for by the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. A third force. Born repulsion, occurs at very small separation distances when electron clouds overlap [1,6,20,21], In emulsion systems an electrical double-layer may form around the disperse phase droplets. While electrical double-layer repulsion is certainly important in o/w emulsions, it does not play a large role in the stabilization of w/o emulsions due to the low dielectric constant of oil [55,56],... 

The contributions from dispersion interactions and electrical double layer interactions are combined in the Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory to give... 

The Derjaguin and Landau and Verwey and Overbeek, DLVO, theory, the most widely accepted for colloidal stability (13,14), is based on a model in which the rate of coagulation is determined by the diffusion of particles toward each other in the presence of a potential field. This field is the result of molecular attractive forces of the Van der Waals type and repulsive forces due to the interaction of the electric double layer around the particles. The attraction between particles immersed in a fluid is considered in this theory to result from London dispersion forces. Hamaker (15) has shown that the magnitude of the potential due to these forces increases rapidly as the particles are brought closer together. 

The stability of nanosized materials in solution can be predicted on the basis of Derjaguin and Landau, Verwey and Overbeek (DLVO) theory, and relevant extensions. Among the different processes occurring in charge of nano-objects in... 

The Yukawa potential is of interest in another connection. According to the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, colloidal... 

Comparison of the proposed dynamic stability theory for the critical capillary pressure shows acceptable agreement to experimental data on 100-/im permeability sandpacks at reservoir rates and with a commercial a-olefin sulfonate surfactant. The importance of the conjoining/disjoining pressure isotherm and its implications on surfactant formulation (i.e., chemical structure, concentration, and physical properties) is discussed in terms of the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of classic colloid science. 

Throughout most of this chapter the emphasis has been on the evaluation of zeta potentials from electrokinetic measurements. This emphasis is entirely fitting in view of the important role played by the potential in the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. From a theoretical point of view, a fairly complete picture of the stability of dilute dispersions can be built up from a knowledge of potential, electrolyte content, Hamaker constants, and particle geometry, as we discuss in Chapter 13. From this perspective the fundamental importance of the f potential is evident. Below we present a brief list of some of the applications of electrokinetic measurements. 

When two charged particles immersed in an electrolyte approach each other, the overlap of their ionic atmospheres (the double layers) generates a repulsive force. The traditional Derjaguin—Landau—Verwey—Overbeek (DLVO) theory assumes that the stability of charged colloids is a consequence of a balance between this double layer repulsion and the attractive van der Waals interactions.1... 

Aggregation of liposomes both in vitro and in vivo is one of their main stability problems. According to the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, or theory of colloidal stability, a colloidal system is stable if the electrostatic repulsion forces between two particles are larger than the attraction van der Waals forces. Therefore charged liposomal formulations are highly desirable. Manipulation of... 

The stability of colloidal systems consisting of charged particles can be essentially explained by the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory [1-7]. According to this theory, the stability of a suspension of colloidal particles is determined by the balance between the electrostatic interaction and the van der Waals interaction between particles. A number of studies on colloid stability are based on the DLVO theory. In this chapter, as an example, we consider the interaction between lipid bilayers, which serves as a model for cell-cell interactions [8, 9]. Then, we consider some aspects of the interaction between two soft spheres, by taking into account both the electrostatic and van der Waals interactions acting between them. 

The potentials (7-1), (7-2), and (7-4a), when combined, form the basis of the celebrated DLVO (Derjaguin and Landau, 1941 Verwey and Overbeek, 1948) theory of colloid stability. This theory is useful in predicting the conditions of surface potential, ionic strength, and so on, under which flocculation will occur. But the theory has important limitations, in part because it only considers van der Waals, electrostatic, and hard-core interactions. 

There is a well-developed theory—the Derjaguin-Landau and Verwey-Overbeek (DLVO) theory—to describe the interaction between particles of a lyopho-bic colloid. This is reviewed in the texts of Hunter (1987) and Hiemenz (1986) and is based on the assumption that the van der Waals interactions (attractive forces) and the electrostatic interactions (repulsive forces) can be treated separately and then combined to obtain the overall effect of both of these forces on the particles. 

It is customarily assumed that the overall particle-particle interaction can be quantified by a net surface force, which is the sum of a number of independent forces. The most often considered force components are those due to the electrodynamic or van der Waals interactions, the electrostatic double-layer interaction, and other non-DLVO interactions. The first two interactions form the basis of the celebrated Derjaguin-Landau-Verwey-Overbeek (DLVO) theory on colloid stability and coagulation. The non-DLVO forces are usually determined by subtracting the DLVO forces from the experimental data. Therefore, precise prediction of DLVO forces is also critical to the determination of the non-DLVO forces. The surface force apparatus and atomic force microscopy (AFM) have been used to successfully quantify these interaction forces and have revealed important information about the surface force components. This chapter focuses on improved predictions for DLVO forces between colloid and nano-sized particles. The force data obtained with AFM tips are used to illustrate limits of the renowned Derjaguin approximation when applied to surfaces with nano-sized radii of curvature. 

Apparently, mechanisms of low-salinity waterflooding are related to the DLVO theory, which is named after Derjaguin, Landau, Verwey, and Overbeek. The theory describes the force between charged surfaces interacting through a liquid medium. It combines the effects of the van der Waals attraction and the electrostatic repulsion due to the so-called double layer of counter ions. 

The force between particles is the sum of a pH-independent van der Waals component, which is always attractive, and a pH-dependent electrostatic component, which can be attractive or repulsive. In Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, the potential is used to calculate the interaction force or energy as a function of the distance between the particles. Atomic force microscopy (AFM) makes it possible to directly measure the force between the particles as a function of the distance, and commercial instruments are available to perform such measurements. Different approaches have been proposed to utilize the results obtained by AFM to determine the pHq. The quantity obtained by AFM corresponds to the lEP rather than the PZC. AFM was used to measure the force between SiO2 (negative potential over the entire studied pH range) and Si,N4 (lEP to be determined) in [681]. The pH at which the force at a distance of 17 nm was equal to zero was identified with the lEP. The van der Waals forces are negligible at such a distance, and the force is governed by an electrostatic interaction. The experimental results were consistent with DLVO theory. 

The forces acting on a colloidal system include gravitational, diffusion, viscous, inertial, attractive Van der Waals, and electrical repulsive forces. Because most of these forces are functions of the particle size, it is important to know both particles size and size distribution. The classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory describes colloid stability on the basis of pair interaction, considering only attractive van der Waals forces and repulsive electrostatic forces (Molina-Bolfvar and Ortega-Vinuesa, 1999). The total potential energy of interaction, Ujc, between two particles is defined as ... 

Whether the colloidal particles encountering each other will flocculate (or coalesce) will generally depend on the net interaction resulting from the combined attractive van der Waals forces and repulsive electrostatic forces resulting from the overlap of the electric double layers. This theory of colloid stability, in considerably more detail than given here, is known as the Derjaguin, Landau, Verwey, Overbeek (DLVO) theory of colloid stability (Hiemenz 1986, Verwey c Overbeek 1948). 

Particle-particle and particle-membrane interactions can be described with the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory which combines van der Waals and electrostatic double layer interactions. While these theories generally apply for smooth surfaces, Bhattacharjee et al. (1998) have... 

According to the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory, a cornerstone of modern colloid science, two types of forces exist between colloidal particles suspended in a dielectric medium (1) electrostatic forces, which result from unscreened surface charge on the particle and (2) 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). 

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