Zeta potential is the electrical potential that exists at the shear plane of a particle, which is some small distance from the surface.
Colloidal particles dispersed in a solution are electrically charged due to their ionic characteristics and dipolar attributes. The development of a net charge at the particle surface affects the distribution of ions in the neighboring interfacial region, resulting in an increased concentration of counter ions (ion of charge opposite to that of the particles) close to the surface.
This double layer may be considered to consist of two parts: a inner region which includes ions bound relatively strongly to the surface and an outer, or diffuse region in which the ion distribution is determined by a balance of electrostatic forces and random thermal motion. The potential in this region, therefore, decays with the distance from the surface, until at a certance distance it becomes zero (see the graph on the left).
|When a voltage is applied to the solution in which particles are dispersed, particles are attracted to the electrode of the opposite polarity, accompanied by the fixed layer and part of the diffuse double layer. The potential at the boundary between this unit, that is to say at the above-mentioned shear plane between the particle with its ion atmosphere and the surrounding medium, is known as the Zeta Potential. |
Zeta potential is a function of the surface charge of a particle, any adsorbed layer at the interface and the nature and composition of the surrounding medium in which the particle is suspended.
The principle of determining zeta potential is very simple.
Most materials when immersed in water exhibit a zeta potential. The majority of demineralized water contaminants, including most colloids, particles, bacteria, and pyrogens (bacterial fragments), are negatively charged. Filter media can be chemically modified to give them a positive zeta potential.