OIA1008 DLVO THEORY

DLVO Theory

Explains colloidal stability by balancing attractive van der Waals forces and repulsive electrostatic (double layer) forces between particles.

Colloidal Stability

The ability of particles in a colloid to remain uniformly dispersed without aggregating or settling.

Van der Waals Forces

Weak attractive forces between all atoms and molecules due to fluctuating polarizations.

Electric Double Layer

Layer of ions surrounding colloidal particles that generates repulsive electrostatic forces to prevent aggregation.

Derjaguin-Landau-Verwey-Overbeek

Scientists who independently developed the DLVO theory in the 1940s (Russia and Netherlands).

Lyophobic Colloids

Colloidal systems that are not stabilized by affinity to the dispersion medium; heavily dependent on electrostatic stabilization.

Entropic Repulsion

Repulsion due to electric double layer formed by ion distribution around particles in a liquid medium.

Primary Minimum

Deep attractive potential energy well; particles at this point may irreversibly aggregate.

Energy Barrier (Primary Maximum)

The peak in interaction energy that must be overcome for particles to come close and aggregate.

Secondary Minimum

A shallow energy well allowing reversible aggregation (e.g., flocculation).

Ionic Strength

Affects the thickness of the electric double layer; higher ionic strength compresses it, decreasing repulsion.

Zeta Potential

Measure of electrostatic potential near the particle surface; higher magnitude indicates better colloidal stability.

Critical Coagulation Concentration (CCC)

Minimum electrolyte concentration needed to cause rapid coagulation of a colloidal system.

Flocculation

Reversible aggregation of particles into loosely bound clusters, typically via secondary minimum.

Coagulation

Irreversible aggregation into compact masses due to overcoming the primary energy barrier.

Bridging Flocculation

Non-DLVO interaction caused by polymer chains linking particles together.

Steric Stabilization

Stabilization via adsorbed polymers that create a steric barrier, preventing particle approach.

Depletion Flocculation

Occurs when free polymers in solution push particles together, creating osmotic imbalance.

Colloidal Dispersion

A system where fine particles are suspended in a continuous phase; stability described by DLVO.

DLVO Theory Application in Paints

Ensures pigment particles remain suspended and evenly distributed.

DLVO Theory in Pharmaceuticals

Used in suspensions to maintain active drug particles in dispersed form for dose uniformity.

DLVO in Food Emulsions

Helps stabilize emulsions like mayonnaise or ice cream by managing droplet interactions.

DLVO and Microbial Adhesion

Describes how microbes adhere to surfaces based on net interaction forces.

DLVO in Membrane Fouling

Used to understand how particles adhere or block filtration membranes in water treatment.

DLVO in Water Treatment

Crucial for coagulation/flocculation steps during clarification of drinking water.

Surface Charge Density

Affects the magnitude of repulsive forces; higher density enhances stability.

Hamaker Constant

A material-specific constant used in calculating van der Waals attraction.

DLVO Theory Limitation

Does not consider steric or hydration forces unless modified (extended DLVO).

DLVO vs. Non-DLVO Forces

DLVO includes van der Waals and electrostatic; non-DLVO includes steric, hydration, and bridging forces.

Total Interaction Energy Curve

Graph combining repulsion and attraction to predict particle behavior.

Double Layer Compression

Occurs with high salt concentration, reducing repulsion and promoting aggregation.

DLVO and Pharmaceutical Suspensions

Helps design stable oral or injectable formulations by preventing particle aggregation.

Environmental pH Impact

Affects particle surface charge and zeta potential, altering stability.

DLVO in Nanotechnology

Guides nanoparticle dispersion stability in biomedical and industrial applications.

DLVO in Cosmetics

Stabilizes emulsions and dispersions in lotions, creams, and shampoos.

Van der Waals Attraction in DLVO

Always present, short-ranged, and contributes to particle aggregation.

Double Layer Repulsion in DLVO

Counteracts aggregation by maintaining distance between particles.

DLVO Potential Energy Curve Features

Includes primary minimum, energy barrier (maximum), and secondary minimum.

DLVO Theory in Biotechnology

Helps in formulation of stable biopharmaceutical suspensions and delivery systems.

Electrolyte Type and DLVO

Multivalent ions (e.g., Ca²⁺) compress double layer more than monovalent (Na⁺), destabilizing colloids faster.