Flocculation kinetics and cluster morphology in illite/NaCl suspensions

Using static and dynamic light-scattering techniques, we investigated the f locculation of geologic specimen illite and soil illite colloids suspended in NaCl solution at pH 8, Our results show that the two universality classe s proposed by Lin and co-workers to characterize the diffusion and reaction -limited regimes of cluster-cluster flocculation do not apply to illite col loids, which have nonspherical morphology. Static light-scattering measurem ents yielded mass fractal dimensions for the soil illite clusters that were significantly above those required by universality. Those for specimen ill ite were influenced by the initial colloid concentration, suggesting that c luster restructuring had occurred during flocculation. Dynamic light-scatte ring measurements revealed a significant departure from linear growth of th e mean cluster size with time, as required by universality in the diffusion -limited regime, and, for specimen illite, an oscillatory dependence of the mean cluster radius on time was observed in the transition from diffusion- limited to reaction-limited flocculation, Overall, the morphology, interact ions, and restructuring of primary particles are believed to be responsible for the departure from universality in the flocculation behavior of the il lite colloids. (C) 2000 Academic Press.