Lowering the zeta potential by applying an external voltage?

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Alan F Rawle

Reducing the voltage (in reality the field as voltage/distance = field) reduces the mobility but not the zeta potential.

Horea Florin Chicinas

Thank you very much! I have watched your lectures on brainshark regarding zeta potential, however certain things are still difficult for me to comprehend. Should reducing the mobility lead to faster sedimentation rate?

Ulf Nobbmann

The electrophoretic mobility is typically measured in a direction perpendicular to sedimentation... If the applied field is very strong it may partially overcome some sedimentation and thus one could say reducing the applied field could lead to "faster" sedimentation (only in the sense that it may be faster than with a stronger applied field). Please note, in most applications, zeta potential measurements are made in a regime where sedimentation does not play a significant role, and thus the two are not really directly related. In sedimentation the settling of particles is observde. In zeta potential the movement of particles in an electric field is observed.

John Francis Miller

@Horea - you ask "Do you believe it is possible to adjust the Zeta potential by applying an external voltage?" which I don't think the other answers address. I assume you mean can you apply an electric field and lower the zeta potential compared to without an electric field? I'd say the answer is no. Applying the field just makes the particles move due to electrophoresis so that you can measure the velocity and estimate zeta potential.

What are you trying to achieve? If you are simply trying to make the zeta potential as small as possible to promote aggregation then you can add electrolyte. It depends on your goal.

I had managed to obtain soft agglomerates by increasing the pH value a little bit, and someone had asked me whether we could obtain the same effect by applying an external voltage. Since I could't find such an answer I tried asking here. I would like to thank you for your answer!