The Effect of Cationic Electrolytes on the Electrostatic Force Between Two Dissimilar Ionizable Surfaces
It is widely recognized that the electrostatic interaction is one of the most important forces (including long-range, short-range and hydrodynamic forces) in promoting or inhibiting adhesion of the colloidal particles in many technological processes such as filtration, paper-making, wastewater clarification and clay migration in oil reservoir. Usually, the effects of electrostatic force on colloidal adhesion follow the rule given by the DLVO theory1. The basic principle of the DLVO theory is that the total interaction energy between two interacting colloidal particles is the sum of the electrostatic repulsive energy and the van der Waals attractive energy. The magnitude of the electrostatic energy depends on the thickness of the electrical double layer and the surface potentials of the interacting particles. In calculating the electrostatic force, it always assumes that the two interacting surfaces are fixed either with constant potential or with constant charge2,3. However, in dealing with the adhesion of colloidal particles bearing with ionizable surface groups, it was pointed out that, for the purpose of minimizing the total interaction free energy, the particles will regulate their surface charges or potentials so that the interacting surfaces can maintain at ionicequilibrium with the bulk solution. Hence, neither the particle potential nor the particle charge remains constant during the period of adhesion 4,5,6,7,8,9. Recently, based on the above charge regulation model, the author 10,11 examined the effect of the presence of multivalent cations on the electrostatic force between a particle bearing with ionogenic groups and a collector with either constant potential or constant charge.
KeywordsDivalent Cation Electrostatic Force Separation Distance Repulsion Force Suspension Medium
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