Examination of the atypical electrophoretic mobility behavior of charged colloids in the low salt region using the O’Brian-White theory |
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Authors: | M Antonietti L Vorwerg |
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Institution: | 1. Max-Planck-Institute of Colloids and Interfaces, Kantstrafie 55, 14513, Teltow-Seehof, Germany
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Abstract: | Polystyrene microspheres having roughly the same size but different negative surface charge densities were prepared by emulsion
polymerization. The amount of sulfate groups on the surface of the particles was controlled by variation of the amount and
the decomposition rate of the initiator used, potassium, persulfate. After the cleaning process involving dialysis and extensive
ultrafiltration the surface-charge density of the samples was determined and their electrokinetic behavior was studied.
A simple model based on the Gouy–Chapman theory and the O’Brian–White approach allows the calculation of the dependence of
the electrophoretic mobility on salt concentration. Comparison of the theoretical and experimental curves showed that they
were in good agreement in a number of qualitative features. Moreover, the model revealed that a monotonously increasing zeta
potential with falling electrolyte concentration results in a mobility maximum, and that this so-called atypical behavior
is in accordance with the standard electrokinetic theory. No ion adsorption mechanism or the existence of a charged hairy
layer, current standard explanations for this anomality, had to be invoked.
Received: 13 February 1997 Accepted: 2 June 1997 |
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Keywords: | Polystyrene latices electrophoretic mobility zeta potential |
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