Electrophoretic Motion of Two Spherical Particles with Thick Double Layers

Area of Science:

• Colloid and Surface Science
• Computational Physics
• Electrochemistry

Background:

• Electrophoretic mobility is crucial for understanding colloidal suspension behavior.
• Existing models often simplify double-layer thickness, limiting accuracy for certain particle systems.
• Numerical calculations are needed to capture complex interactions in concentrated suspensions.

Purpose of the Study:

• To numerically calculate electrophoretic mobilities of interacting spheres with arbitrary double-layer thickness.
• To derive a general formula for N interacting particles under low zeta-potential conditions.
• To quantify the impact of particle interactions on suspension electrophoretic mobility.

Main Methods:

• Numerical computation of electrophoretic mobilities for two interacting spheres.
• Derivation of a general formula for N interacting particles (low zeta potential).
• Comparison with reflection calculations and computation of O(phi) contribution to mobility.

Main Results:

• Particle interactions become significant for scaled particle radius (kappa*a) <= 10.
• The O(phi) contribution to mobility can increase 2-3 fold for kappa*a = 1 compared to thin double layers.
• Fluctuations in electrophoretic velocity are approximately 10% of the mean velocity.
• Pair interactions, even for thick double layers, are not excessively large.

Conclusions:

• Numerical methods provide accurate electrophoretic mobility data for thick double layers.
• Particle interactions influence suspension mobility, particularly at smaller scaled radii.
• The study refines understanding of colloidal interactions in electrophoretic systems.