The Electrical Double Layer Force between Spherical Particles Which Are Partially Submerged in Water

Area of Science:

• Colloid and Surface Science
• Physical Chemistry
• Electrochemistry

Background:

• Colloidal particles adsorb to electrolyte solution surfaces, crucial for applications like Pickering emulsions.
• These particles experience capillary and electrical double layer (EDL) forces due to ion overlap near surfaces.
• The EDL force arises from interactions between particle surfaces and the electrolyte solution's charged free surface.

Purpose of the Study:

• To elucidate the contribution of the electrolyte solution's free surface to the EDL force between two half-submerged spherical particles.
• To provide a mathematical framework for calculating this EDL force, including approximations for practical use.

Main Methods:

• Solving the linearized Poisson-Boltzmann equation to determine the excess electrical potential near the particles.
• Integrating excess Maxwell and osmotic stresses to quantify the resulting EDL force.
• Developing Páde approximations for simplified EDL force calculations.

Main Results:

• Quantified the EDL force component originating from the electrolyte solution's free surface.
• Developed accurate analytical solutions and approximations for the EDL force.
• Demonstrated the significant role of the free surface in inter-particle EDL interactions.

Conclusions:

• The free surface of an electrolyte solution significantly influences the electrical double layer force between adsorbed colloidal particles.
• The derived mathematical framework and approximations simplify the calculation of EDL forces in similar systems.
• This work provides valuable insights for controlling particle interactions in surface-adsorbed systems and Pickering emulsions.