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Comparison of the Zeta Potential with the Diffuse Layer Potential from Charge Titration
 

Summary: Comparison of the Zeta Potential with the Diffuse Layer
Potential from Charge Titration
Phil Attard,* D. Antelmi, and I. Larson
Ian Wark Research Institute, University of South Australia, Mawson Lakes, SA 5095 Australia
Received April 23, 1999. In Final Form: October 21, 1999
The hypernetted chain (HNC) theory is used to compare charge titration and zeta potential data for
several colloids. It is found that the HNC diffuse layer potential is closer to the zeta potential than that
calculatedwiththetraditionalPoisson-Boltzmann(PB)approximation,andhencetheamountofcounterion
binding required to bring the two into conformity is reduced. Further improvement is obtained by using
an effective PB diffuse layer potential, calculated from both the numerical HNC theory and the analytic
extended PB approximation. The rationale for using the effective PB potential is that the conversion from
the measured electrophoretic mobility to the zeta potential invokes the PB approximation. In the case of
silver iodide quantitative agreement is obtained without any fitting parameters, which confirms that no
counterion binding occurs. For the metal oxides analyzed (titanium dioxide, aluminum oxide, and silicon
dioxide) the two measurements can only be reconciled by postulating counterion binding or surface charge
mobility.
Introduction
The electric double layer plays a major role in diverse
areas such as adhesion, self-assembly, filtration, wetting,
electrokinetics, and it is perhaps the major determinant

  

Source: Attard, Phil - School of Chemistry, University of Sydney

 

Collections: Chemistry