Attractive and Electrical Interaction DLVO Theory

COMBINED ATTRACTIVE AND ELECTRICAL INTERACTION DLVO THEORY 

In the absence of adsorbed polymeric molecules, which are discussed below, colloid stability is governed in many cases by the combination of London-van der Waals attractive forces and the repulsive forces produced by double-layer overlap. This concept is the basis of the famous DLVO theory, developed independently in the late 1930s and early 1940s by Derjaguin and Landau in the Soviet Uruon and by Verwey and Overbeek in the Netherlands. 

To find the total interaction energy between two particles we simply add the contributions cp and from attractive and electrical effects. For example, the total interaction energy per unit area between identical semi-infinite blocks can be foimd from Equations 3.5 and 3.48  

FIGURE 3.11 ] is shown here with varying electrolyte strengths (k per centimeter). The sphere radii are 1000 A, Ag = 10 ergs, and = 25 mV. Reprinted from Verwey and Overbeek (1948) with permission. 

A mqor success of the DLVO theory has bear its ability to predict the very large and striking effect of countraion valraice on coUoid stability. To see this, we focus on the maximum in the Ef- curve. We first use Equation 3.58 to find the separation distance at which vanishes. The result is 

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