Electrical Properties of Colloids - Key electrical properties

Electrical Properties of Colloids explain charge, electrophoresis, and electro-osmosis in dispersions.
Colloidal particles typically carry a surface charge when dispersed in a medium.
Electrical Properties of Colloids determine stability and behavior of colloidal systems.
This charge influences their stability, interactions, and movement under electric fields.

Colloidal particles acquire a surface charge that attracts oppositely charged ions, forming an electric double layer:
- Fixed layer: Tightly bound counterions directly attached to the particle surface.
- Diffuse layer: Loosely associated, mobile ions surrounding the fixed layer.
This double layer affects interparticle forces and plays a major role in colloidal stability.

Zeta potential is the electrical potential at the shear plane between the fixed and diffuse layers of the electric double layer.
It is a key indicator of colloidal stability:
- High ζ-potential (positive or negative): Strong electrostatic repulsion → Stable colloid
- Low ζ-potential: Weak repulsion → Particle aggregation or flocculation
Pharmaceutical relevance: Zeta potential measurements are crucial for evaluating and optimizing the stability of formulations.

Refers to the movement of charged colloidal particles under the influence of an electric field.
- The direction of movement reveals the nature of the surface charge (positive or negative).
- It is used to study particle charge, mobility, and helps in formulation optimization.

Describes the movement of the dispersion medium (not the particles) under an electric field, typically when particles are immobilized (e.g., in a filter bed).
- This is the opposite of electrophoresis.
- It is useful in analyzing surface charge characteristics and ionic interactions at interfaces.