Solvent-mediated nonelectrostatic ion-ion interactions predicting anomalies in electrophoresis

Area of Science:

• Physical Chemistry
• Colloid Science
• Electrokinetics

Background:

• Electrophoretic mobility is crucial for understanding charged particle behavior in fluids.
• Existing models, like Henry's approach, often underpredict particle velocity.
• The role of nonelectrostatic interactions in electrophoretic mobility is not fully understood.

Purpose of the Study:

• To investigate the impact of solvent-mediated nonelectrostatic ion-ion interactions on electrophoretic mobility.
• To develop an analytical solution for electrophoretic mobility incorporating these interactions.
• To compare the new model with the standard Henry's approach and experimental data.

Main Methods:

• Linearization of governing equations for low surface electrostatic potential.
• Derivation of a closed-form analytical solution for electrophoretic mobility.
• Comparison of theoretical results with experimental observations and Henry's model.

Main Results:

• The proposed model, including nonelectrostatic interactions, accurately predicts particle velocity, resolving experimental discrepancies.
• Nonelectrostatic interactions significantly alter electrophoretic mobility compared to standard models.
• The model explains the observed phenomenon of electrophoretic mobility reversal.

Conclusions:

• Accounting for solvent-mediated nonelectrostatic ion-ion interactions is essential for accurate electrophoretic mobility prediction.
• The developed analytical solution provides a more robust framework for understanding electrokinetic phenomena.
• This work reconciles theoretical predictions with experimental findings, particularly regarding mobility reversal.