Video Processing Electrophoretic Measurements under High Electric Fields for Sub-millimeter Particles in Oil

Area of Science:

• Electrochemistry
• Materials Science
• Physical Chemistry

Background:

• Electrokinetic properties (mobility, surface charge, zeta potential) are crucial for industrial applications.
• Studies have extensively focused on aqueous media, leaving organic solvents less explored.
• Understanding these properties in organic solvents is vital due to their increasing industrial relevance.

Purpose of the Study:

• To develop a method for measuring electrokinetic properties of sub-millimeter particles in organic solvents.
• To investigate particle behavior in cyclohexane, a solvent with very low permittivity.
• To analyze charge densities and mobilities of various organic particles in non-aqueous media.

Main Methods:

• Designed a specialized electrophoresis cell with a microscope monitor for particle tracking.
• Utilized high electric fields (up to 1100 V, 55 kV/m) to observe particle movement.
• Employed image processing to calculate electrophoretic mobilities of particles ranging from 4 to 478 µm.

Main Results:

• Successfully traced movement of large sub-millimeter particles (4–478 µm) in cyclohexane without surfactants.
• Measured electrophoretic mobilities in the range of 10⁻⁹ to 10⁻⁷ m²/V·s.
• Determined charge densities for five organic particles between -3.5 and 4.4 e/µm², with polyethersulfone showing high mobility.

Conclusions:

• The developed method enables electrokinetic studies of large particles in low-permittivity organic solvents.
• Particle surface charge in these solvents is primarily influenced by hydroxide dissociation or protonation of oxygen atoms.
• Findings provide essential data for applications involving organic particle manipulation in non-aqueous systems.