Using a turbidimetric method to study the kinetics of agglomeration of potassium sulphate in a liquid medium

Abstract : Turbidimetry is used to characterize the kinetics of agglomeration of a finely ground sample of potassium sulphate in different stirred media, i.e. water and several organic liquids. The sensor used in this study is most sensitive to particle diameters near 1 μm. When particles in this size range agglomerate, their contribution to the global turbidity τ(t) decreases or vanishes. This paper shows that the knowledge of the initial slopes of τ(t) for different masses of solid samples is sufficient to calculate the order and to estimate the constant of the kinetic law of agglomeration. Agglomeration is proved to depend strongly on the nature of the medium and may be linked to the zeta potential. The influence of the stirring rate on the kinetic constant and on the shape of the agglomerates is also studied. A discussion is presented in relation to the classical models of agglomeration in turbulent flows. The primary particles (0.5–2.5 μm) are smaller than the Kolmogoroff microscale of turbulence (6–8 μm), but the final clusters are larger (50 μm). The calculated kinetic constants are greater than the experimental values. The changes in the geometry of the clusters are interpreted too.