Zeta potential is the charge located at the slipping point of a particle in suspension. It indicates the stability of colloidal dispersions, with higher magnitudes of zeta potential (above 30mV) resulting in more stable suspensions. While it cannot be calculated directly, zeta potential can be measured using electrokinetic effects like electrophoresis and electroosmosis under an applied electric field. This involves using a laser beam, electrodes, and photomultiplier to analyze the particle movement in relation to the liquid and derive the zeta potential value. Zeta potential is important for understanding dispersion and aggregation processes in various applications including water purification and formation of inks.

1. Zeta Potential

2. Introduction
• Zeta potential is the charge that is located at the slipping
point of a particle in a medium.
• Zeta potential is used mostly in Colloidal chemistry.
• If the magnitude of zeta potential is > 30mV then it is in
stable suspension
• pH has a major effect on the system
• Zeta potential can not be calculated directly.
• However using Electro kinetic effects zeta potential can
be measured

3. Zeta Potential system(general)
• He/Ne laser, goes to a beam splitter which then sends the
beam to a fixed mirror and a modulator.
• Then the beams head into the sample with an electrode
on both ends.
• Then a photomultiplier picks up the signal and sends it to
a computer.

4. Electro Kinetic Effects
• Electro kinetic potential is caused by the interfacial
double layer within a solution.
• The double layer has a stern layer and a diffuse layer.
• Using an electric field either electrophoresis or electro
osmosis will cause the particles to move

5. Electrophoresis
• Under an applied electric field the movement of charged
particles in relation to the liquid its suspended in is
measured
• The velocity of the movement depends on the strength of
the field, dielectric constant, viscocity, and zeta potential
• Using Henry’s law zeta potential can be measured

6. Electro Osmosis
• Movement of charged particles relative to a stationary
charged surface
• Similar to electrophoresis an electric field is applied and
the charged particles begin to move.
• A reverse flow is used to counter the flow of the liquid
system when the field is applied

7. • One problem is that there is only two places where there
is truly the electro osmosis effect
• M3 measurment-Using LDV
• Slow Field Reversal (SFR)
• Fast Field Reversal (FFR)

8. Zeta Potential uses
• Zeta potential can be used as a means to tell how stable a
colloid being analyzed is.
• Zeta potential is key to understanding dispersion and
aggregation processes in water purification, ceramic slip
casting and the formation of inks, paints and cosmetics.
• Often the only way to charecterize double layer
properties

9. Benefits
• A good way to find the characteristics
of the double layer in a colloidal
mixture.
• This also allows you to see how stable
the colloid being analyzed is.
Limitations
• Zeta Potential can not be directly
measured.
• When finding the Zeta Potential the
size of the double layer must be very
thin.

10. Electrical Properties of Colloids Electrical Double Layer and
Zeta Potential
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• A double layer (DL, also called an electrical double layer, EDL) is a
structure that appears on the surface of an object when it is
exposed to a fluid.
• The DL refers to two parallel layers of charge surrounding
the object
• The first layer, the surface charge (either positive or negative),
comprises ions adsorbed onto the object.The second layer is
composed of ions attracted to the surface charge via the coulomb
force,

12. 12
• This second layer is loosely associated with the object. It is made of free ions that
move in the fluid under the influence of electric attraction and thermal motion
rather than being firmly anchored. It is thus called the "diffuse layer".
• DLs play a fundamental role in many everyday substances. For instance,
homogenized milk exists only because fat droplets are covered with a DL that
prevents their coagulation into butter

13. 13
Zeta potential
• zeta potential, donated by the Greek letter zeta
• (ζ), is the potential difference between the dispersion medium and the
stationary layer of fluid attached to the dispersed particle.
• The zeta potential is a key indicator of the stability of colloidal
dispersions
• The magnitude of the zeta potential indicates the degree of electrostatic
repulsion between adjacent, similarly charged particles in a dispersion

14. • When the potential is small, attractive forces may exceed this
repulsion and the dispersion may break and flocculate. So, colloids
with high zeta potential (negative or positive) are electrically
stabilized while colloids with low zeta potentials tend to coagulate or
flocculate as outlined in the table

15. • Diagram showing the ionic concentration and potential difference as a
function of distance from the charged surface of a particle suspended in a
dispersion medium
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16. 16 Lec8,Colloids,SayedA.Rahman