I thought ultrasonic will disperse the particles hence smaller particle size will be measured over times but it happens otherwise. This also happens when i try to precipitate in waterbath at increased temperature. somehow when there is excess of energy, particle size increased. why?
What are the particles? You talk about a solution - i.e. no particles. Sonication increases collision frequency and if the zeta potential in inadequate for small particles in suspension then agglomeration will result due to attractive van der Waals forces.. Often happens with calcium carbonate which is positively charged at neutral pH.
Thank you for your answer Mr. Rawle. May i know how can i measure the zeta potential so i can estimate adequate zeta potential for the suspension to remain dispersed and less agglomeration will occur.
I assume you mean suspension and not solution in your original question. There is no concept of zeta potential for a solution. What do you mean by 'stay dispersed'? If you mean stay in (colloidal) suspension then the size will need to be small. Carry out a Stokes' Law calculation and find out what this maximum size is.
You can measure zeta potential with an appropriate instrument, for example: https://www.malvern.com/en/products/measurement-type/zeta-potential
In order to preserve stability you'll need to adjust the pH or use an additive such as phosphate in the optimum concentration. See slides 44 onwards in:
Nov 11th, 2008. Dispersion and nanotechnology http://tinyurl.com/hpywsge
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