TWL+DLVO+theory

__**DLVO THEORY **__

 v **D **eryagin, **L**andau, **V**ewey and **O**verbeek developed a theory of the stability of colloidal systems (**DLVO theory**) in the 1940s.  v //Assumptions of DLVO theory: // 1. Dispersion is dilute. 2. Only two forces act on the dispersed particles: Van der Waals force and electrostatic force. 3. The electric charge and other properties are uniformly distributed over the solid surface. 4. The distribution of the ions is determined by the electrostatic force, Brownian motion and entropic dispersion. v The theory states that the colloidal stability is determined by the potential energy of the particles (VT) summarizing two parts: potential energy of the attractive interaction due to van der Waals force VA and potential energy of the repulsive electrostatic interaction VR: **VT = VA + VR**  v <span style="font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%;">DLVO Theory suggest that’s that electrical double-layer repulsion will stabilize the emulsion, when the electrolyte concentration phase is less than a certain value. v <span style="font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%;">The minimum of the potential energy determines the distance between two particles corresponding to their stable equilibrium. v <span style="font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%;">The two particles form a loose aggregate, which can be easily re-dispersed. v <span style="font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%;">The strong aggregate may be formed at a shorter distance corresponding to the primary minimum of the potential energy (not shown in the picture). v <span style="font-family: 'Times New Roman','serif'; font-size: 14pt; line-height: 115%;">In order to approach to the distance of the primary minimum the particle should overcome the potential barrier.