This presentation discusses zeta potential and its determination. Zeta potential is defined as the potential difference between the dispersion medium and stationary layer of fluid attached to dispersed particles. There are several methods to determine zeta potential including electrophoresis, streaming potential, and electro-osmosis. Zeta potential is a key indicator of stability in colloidal dispersions - higher zeta potential leads to more electrostatic repulsion and stability against aggregation. Zeta potential has applications in areas like water purification, minerals processing, emulsions, and pharmaceuticals.

1. PRESENTED BY:
KHONDAKER AFRINA HOQUE
ID:1114015 , REG:900048
Department of chemistry
Comilla university.
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2. PRESENTATION ON
ZETA POTENTIAL & ITS DETERMINATION
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3. Overview
Introduction
Determination of zeta potential
Application of zeta potential.
Stability of colloid & zeta potential.
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4. Introduction
Definition:
Zeta potential is the potential difference
between the dispersion medium and the
stationary layer of fluid attached to the
dispersed particle.
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5. Because of the
distribution of the charge
around the particle,
there is a difference in
potential between the
stationary layer and the
bulk of solution across
the diffuse layer. This is
called Electrokinetic or
Zeta potential.
Fig : the electrical double
layer
& zeta potential.
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6. Determination of zeta potential
The zeta potential of a particle is calculated from
electrokinetic phenomena such as :
electrophoresis,
Streaming potential
electro-osmosis
and sedimentation potential
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7. Electrophoresis
The zeta potential, § (potential at the
shear plane), is calculated by using the
Smoluchowski equation.
for spherical particles, which can be treated as point
charges, as follows:
where UE ,the mobility under an applied potential E,
εis the permittivity of the electrolyte medium, and
ɳ is the viscosity of the medium.
The movement of sol particles
under an applied electric potential
is called electrophoresis or
cataphoresis.
Fig: electroporesis
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8. Streaming potential
When the liquid is forced to flow through the capillary or
the plug, by an applied pressure , an E.M.F is developed
which is called the streaming potential.
If E is the potential difference developed across a capillary of radius
a and length /, for an applied pressure difference p, we can write
the following:
Where,
ε is the permittivity of the medium,
ζ is the zeta potential,
ɳ is the viscosity of the liquid, and
K0is the conductivity of the electrolyte solution.
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9. Electro-osmosis
The movement of the
dispersion medium under the
influence of applied potential
is known as electro-osmosis.
Fig: electro-osmosis
 the dispersed phase is kept, stationary,
the medium is actually found to move to
the electrode of opposite sign that its own.
When the applied pressure exceeds the
zeta potential, that diffuse layer moves and
causes electro-osmosis.
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10. When sedimentation of suspend colloids occurs,
this rise a potential difference
This technique is the least commonly used for the determination of
zeta potential, because of several limitations associated with the
measurement and calculation of the zeta potential.
Sedimentation potential
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11. Stability of colloid & zeta potential.
•Key indicator of the stability of
colloidal dispersions.
•Magnitude of zeta potential
indicates the degree of electrostatic
repulsion between adjacent &
similarly charged particles.
•Higher zeta potential- higher
stability-lower aggregation.
•Lower zeta potential- lower
stability-flocculation occurs.
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12. Application of zeta potential.
Water purification & industrial waste.
Minerals and ore flotation.
Emulsions.
Detergency.
Paints.
Pharmaceuticals.
Biomedicals ….etc.
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13. Thanks To All
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14. Question?
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