Separation of charge-regulated polyelectrolytes by pH-assisted diffusiophoresis

Area of Science:

• Colloid and Interface Science
• Physical Chemistry
• Separation Science

Background:

• Colloidal particle separation is crucial in various scientific and industrial applications.
• Diffusiophoresis and electrophoresis are key techniques for manipulating charged particles in solution.
• Understanding the influence of gradients on particle behavior is essential for optimizing separation processes.

Purpose of the Study:

• To evaluate the potential of pH-assisted diffusiophoresis for separating colloidal particles.
• To compare the separation efficiency of pH-assisted diffusiophoresis with pH-assisted electrophoresis.
• To investigate the role of pH and salt gradients on the diffusiophoretic mobility of polyelectrolytes.

Main Methods:

• Simulations were performed on spherical polyelectrolytes (PEs) in an aqueous solution with a KCl background salt.
• A simultaneous salt and pH gradient was applied to induce pH-assisted diffusiophoresis.
• The dependence of particle velocity on pH was analyzed and compared to electrophoresis.

Main Results:

• Particle velocity in pH-assisted diffusiophoresis shows a higher sensitivity to pH changes than in pH-assisted electrophoresis.
• Effective separation of two polyelectrolyte types with different dissociation constants was demonstrated.
• Diffusiophoretic velocities of PEs can be enhanced or reduced by adjusting pH gradients.

Conclusions:

• pH-assisted diffusiophoresis presents a promising and potentially more efficient method for colloidal particle separation.
• The technique allows for tunable control over separation by manipulating diffusiophoretic velocities.
• This approach offers advantages over traditional pH-assisted electrophoresis for separating particles with varying properties.