DLVOteorian

DLVOteorian, commonly referred to as the DLVO theory, is a framework in colloid science that describes how charged particles in electrolytes interact and how colloidal stability arises. Developed in the 1940s and 1950s by Boris Derjaguin, Lev Landau, Egor Verwey, and Th. G. Overbeek, it explains aggregation and stabilization of colloids through competing forces.

The theory posits that the total interaction potential between particle surfaces is the sum of long-range electrostatic repulsion and short-range van der Waals attraction. Mathematically, V(h) = V_el(h) + V_vdW(h), where h is the surface-to-surface separation. Electrostatic double-layer repulsion results from overlapping ionic atmospheres around charged particles in an electrolyte; its magnitude depends on surface charge density, ionic strength and valence, dielectric constant, and pH. Van der Waals attraction arises from correlated fluctuations of dipoles in the particle materials and the surrounding medium; it depends on the Hamaker constant and geometry.

Equilibrium behavior follows from the resultant energy profile. A high energy barrier prevents aggregation and yields stability; a diminishing barrier or a primary minimum leads to coagulation or flocculation. A shallow secondary minimum can cause reversible aggregation.

Limitations include assumptions of smooth, homogeneous surfaces, constant charge or potential, and pairwise additivity; non-DLVO forces such as steric, hydration, and structural forces may be important, especially in complex media. Extensions address non-spherical particles, concentrated suspensions, and dynamic conditions.

Applications span formulation science and process engineering, including paints, foods, pharmaceuticals, and mineral processing, where control of colloidal stability is essential.