Applicability of Optical Methods to Investigate the Kinetics of Flocculation of Montmorillonite Suspension

Abstract

Optical methods, i.e., the classical light absorbance and dynamic light scattering (DLS) were tested in order to clarify the applicability to study the kinetics of flocculation of montmorillonite suspension (pH=10.0 ± 0.5). The validity of these methods was confirmed by flocculation experiments of the standard latex dispersion. For a suspension of montmorillonite, it was found that (i) the electrolyte (NaC1) concentration which corresponds to the crossover between dispersion and flocculation was between 1.0 ×10^-2N and 3.0 ×10^-2N, (ii) in the range of low electrolyte concentration, qualitatively the same result was obtained by these two methods for the rate of flocculation compared with the electrolyte concentration, (iii) in the range of high electrolyte concentration, it was clarified that DLS was more effective during the process of the rate of flocculation measurement used in this study, however it was impossible to obtain an exact rate of flocculation in this range. On the basis of these results, the possibility of future improvement was discussed to obtain the reliable data of the rate of flocculation of montmorillonite suspension in the region of high electrolyte concentration.