Zeta ppt

PRESENTED BY:
KHONDAKER AFRINA HOQUE
ID:1114015 , REG:900048
Department of chemistry
Comilla university.
12/14/2018 1

PRESENTATION ON
ZETA POTENTIAL & ITS DETERMINATION
12/14/2018 2

Overview
Introduction
Determination of zeta potential
Application of zeta potential.
Stability of colloid & zeta potential.
12/14/2018 3

Introduction
Definition:
Zeta potential is the potential difference
between the dispersion medium and the
stationary layer of fluid attached to the
dispersed particle.
12/14/2018 4

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.
12/14/2018 5

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
12/14/2018 6

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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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.
12/14/2018 8

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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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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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.
12/14/2018 11

Application of zeta potential.
Water purification & industrial waste.
Minerals and ore flotation.
Emulsions.
Detergency.
Paints.
Pharmaceuticals.
Biomedicals ….etc.
12/14/2018 12

Zeta ppt

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Zeta ppt