Debye-Huckel constant and average particle size of a colloidal dispersion of solid aggregates. Evaluation of κ〈r〉 to characterize repulsive DLVO-based interactions. Application to the Si3N4/H2O (1) system

The Debye-Huckel constant κ for Si3N4/H2O (1) dispersed systems at different pH values of the liquid phase and at different solid weight concentrations has been experimentally determined by titration and can be expressed as a helpful power law of the concentration c± of H+/OH− ions left in solution. On the basis of the results of a previous study, which determined the average radius of the agglomerates 〈r〉, the order of magnitude of the product κ〈r〉, basic to characterizing the electrostatic interactions between agglomerates, is evaluated over wide pH and solid weight concentration ranges. As a result, for the investigated silicon nitride aqueous suspensions, one obtains κ〈r〉 ≈ [1–10], corresponding to medium-sized solid particles and strong electrolyte solutions. The procedure described here is suitable for any colloidal system when non-DLVO effects and chemisorption-induced phenomena are negligible.