title: Absolute aggregation rate constants in aggregation of kaolinite measured by simultaneous static and dynamic light scattering.
abstract: The aggregation rate was determined for the < 0.2 microm size fraction of kaolinite (KGa-2) using simultaneous static and dynamic light scattering at pH 9.5. It was found that method suggested by Holthoff et al. [Langmuir 1996, 12, 5541] is suitable for determination of the absolute aggregation rate constant of a clay dispersion without using the particle optical factors. The determined fast aggregation rate constant is k11,fast = (3.7 +/- 0.2) x 10(-18) m3 s(-1). Stability behavior of kaolinite colloids was studied as a function of concentration of sodium chloride by simultaneous static and dynamic scattering. The critical aggregation concentration was found to be 0.085 +/- 0.005 mol dm(-3). When calculating the relationship between the stability ratio and the electrolyte concentration using the DLVO theory, the best fit to the experimental data was achieved with a Hamaker constant of A = (4.7 +/- 0.2) x 10(-20) J.
authors.affiliation: Department of Chemistry and Biochemistry, South Dakota State University, Brookings, South Dakota 57007-0896, USA.
authors.forename: Marta
authors.initials: M
authors.lastname: Berka
authors.forename: James A
authors.initials: JA
authors.lastname: Rice