Zeta potential meter
Zeta
potential is a measure of the magnitude or attraction between particles. Its measurement brings detailed insight into
the dispersion mechanism and is the key to electrostatic dispersion control.
Manufacturer:
The Malvern Instruments, UK
Model:
Zetasizer 2000
What is Zeta Potential?
Most
particles in a polar medium such as water will possess a surface charge.
A charged particle
will attract ions of the opposite charge in the dispersant, forming a strongly
bound layer close to the surface of the particle. Those ions further away
from the core particle make up a diffuse layer, more loosely bound to the
particle. Within this diffuse layer is a notional boundary, inside which
the particle and its associated ions act as a single entity, diffusing through
the dispersion together.
The plane at
this boundary is known as the surface of hydrodynamic shear, or the slipping
plane. The potential at this boundary is known as the zeta potential.
It is important to note that the magnitude of the zeta potential is affected
by both the nature of the surface of the particle, and the composition of
the dispersant.
A
charged particle dispersed in liquid containing ions will change the distribution
of ions in its vicinity.
There are 2 mechanisms that affect this interaction:
1)
The particle is charged. If the magnitude of this charge is great
enough, the repulsion between particles will ensure the dispersion
will resist flocculation. This is electrostatic stabilization. When this
repulsion is not high enough, the attractive Van der Waals forces always
present in the dispersion can cause flocculation or coagulation to occur.
2)
Steric stabilization may be present. This is where a surface
coating on the particles prevents them from approaching too closely.
-
Streric stabilization is usually achieved by adding polymers to the system. This is a simple solution to the dispersion problem, but these polymers may not be desirable in the final formulation, and many applications require the careful control of the balance between dispersion and flocculation, which is difficult using this method.
Electrostatic
stabilization has a number of advantages.
It can be ‘tuned’ for the particular application, it is reversible
and potentially cheap as often just a change in the concentration of a few
ions is required.
Key
Features:
-
-
Both polar and non-polar solvents can be used
-
The change of pH, ionic strength or concentration of another additive using an optional auto-titrator.
Applications:
-
Measurement of Zeta potentials of colloidal/ nano-particles and macromolecules
-
Some
specific applications can be summarised as follows:
§
Avoid caking of suspensions:
Determine effect of each component in a formulation on sedimentation, predict
shelf life, improves batch-to-batch consistency.
§
Enhance the strength
of ceramics: Achieve a uniform dispersion;
ensure a dense, strong and consistent product.
§
Maximise
recovery in mineral processing: Improve the efficiency of froth flotation processes,
understand the effect of additives, and optimize pre-processing.
§
Prevent creaming: Formulate
intravenous lipid emulsions for specific patient regimes.
§
Improve toners and inks: Select
the correct dispersant for toners and inks to minimize aggregation.
§
Speed up flocculation
measurement: Control flocculation in
fermentation processes and make measurements in less than a minute.
§
Customize
formulation for local requirements: Use
zeta potential measurements to ensure agrochemical concentrates are compatible
with dilution by local water sources.
Accessories:
1) Optional Auto-titrator
2) Transfer standards
are packaged in 10ml syringes ready for use.
Ř This
standard is used to verify the correct operation of all Malvern
systems that measure zeta potential in a capillary cell.
3) The samples are
supplied in ready to use syringes, removing any concern about standard preparation.
