I am working with a system that injects air bubbles into sludge under very high velocity (high shear rate) and high-pressure conditions which may lead to shearing sludge particles. Can this also change sludge particles charge density and zeta potential?
Check the pH before and after the introduction of air. It could be saturation of dissolved CO2. The particles may have a pH-dependent zeta potential.
Thanks, Farid Benyahia
! I placed a request to receive the paper and hopefully will get it soon however, I am mostly trying to study the effects on the sludge particle's ZP rather than the bubble's. Do you think the change in ZP of bubbles would also affect the ZP of particles?
Thanks, John Francis Miller! That's a very good idea to look at the pH as it's an indicative of changes in zeta potential and it's easy to measure. Do you think a change by a physical factor could be big enough to show itself in pH numbers and not get mistaken with the errors of pH meter? Again, thanks for your inputs.
A couple of things to consider.
What the starting pH is.
Is there any buffering capacity of the sludge?
What the starting zeta potential is.
Consider a pH 8 solution of KOH(aq) in a 500ml bottle that is stirred with a magnetic bar. Just the stirring will dissolve CO2 quickly. The pH will change rapidly (minutes) and reach approx. 5.5. The zeta potential of any dispersed particles may change considerably, too.
I would suggest that if your starting pH is more than one unit greater or less than the pH after air injection then you should consider the possible that the zeta potential will change if the pH is near to the isoelectric point for the particles.
Regarding air bubbles, if they are present when you make your zeta potential measurements, they may interfere. It will depend on the relative amounts of the bubbles and particles, and the technique you are using. With light scattering, for example, bubbles will scatter the light very strongly and make measurement very difficult and unreliable. You may also have small bubbles adsorbed on the particles, too.
A question: what will you use the zeta potential data for?
John Francis Miller Thanks, again and sorry for my late response!
Great information, very useful! My goal is to see any improvements in sludge particles settling after putting air into the sludge stream and letting the air out of the system.
So, you believe if the zeta potential has been changed, we surely will see the effects by the changes in pH of solution or in other words, if I don't see any change in pH, I shouldn't even test the sludge for before&after zeta potential numbers, right?
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