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Modified colloidal primitive model as a homogeneous surface charge distribution: ζ-potential.
Héctor M Manzanilla-Granados1, Marcelo Lozada-Cassou
1Escuela Superior de Computo, Instituto Politécnico Nacional , U. P. Adolfo López Mateos, Ciudad de México, 07738, México.
The Journal of Physical Chemistry. B
|August 21, 2013
Summary
A new theory for colloidal dispersions reveals that smearing particle charges on the surface (modified colloidal primitive model) yields different results than central charges (colloidal primitive model). This impacts zeta-potential and colloid interactions.
Area of Science:
- Colloid and Interface Science
- Physical Chemistry
- Computational Physics
Background:
- Colloidal dispersions are crucial in various scientific and industrial applications.
- Understanding inter-colloid forces is key to predicting dispersion behavior.
- Existing models like the colloidal primitive model (CPM) make simplifying assumptions about charge distribution.
Purpose of the Study:
- To develop an integral equations theory for finite concentration colloidal dispersions.
- To apply this theory to a modified colloidal primitive model (MCPM) with surface-smeared charges.
- To compare MCPM results with the traditional CPM (central charges) for key properties.
Main Methods:
- Derivation of an integral equations theory.
- Application to a modified colloidal primitive model (MCPM) and comparison with the colloidal primitive model (CPM).
- Calculation of zeta-potential, induced charge, and colloid-colloid electric effective force.
Main Results:
- Significant quantitative and qualitative differences observed between MCPM and CPM for zeta-potential and effective forces.
- MCPM yields a positive zeta-potential, while CPM yields a negative one, implying opposite electrophoretic mobilities.
- Both models predict long-range colloid-colloid correlations and oscillatory, attraction-implying forces.
Conclusions:
- The MCPM, with surface-smeared charges, offers a potentially more accurate representation for certain colloidal systems.
- Charge distribution significantly influences colloidal behavior, including electrophoretic mobility.
- Long-range attractions exist between like-charged colloids, consistent with simulations.
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