Study On The Diffusion Properties Of Charged And Permeable Colloidal Particles In Suspensions

Diffusion properties of colloidal particles are key parameters in chemical engineering and transport process. To measure the diffusion properties of colloidal particles is significant. At present, the main method used to study the diffusion properties of colloidal particles is dynamic light scattering. But the traditional dynamic light scattering method only applies to dilute solutions. For dense media, multiple scattering effects become dominant. At this time, single scattering theory is no longer suitable. A phase-modulated fiber optic low-coherence dynamic light scattering device is established which is suitable to investigate the diffusion properties of colloidal particles in dense suspensions.The influence of electrolytes on the diffusion properties of charged colloidal particles in dense suspensions is measured by means of phase-modulated fiber optic low-coherence dynamic light scattering. Polystyrene colloidal particles is used in the experiment. In our experiments, both NaCl and BaCl2are used as electrolytes. Experiment results show that the diffusion coefficients of the polystyrene colloidal particles increase with the increasing of ion concentration and ion valence when the concentration of electrolyte is below0.01mol/L and the temperature keeps constant. The diffusion coefficients obtained experimentally show good agreement with the diffusion coefficients obtained by using the Stern model.On the other hand, the influence of permeability and partilce size on the diffusion properties of the permeable colloidal particles is also investigated. The results show that both permeability and particle size affect the diffusion properties. And we point out that the diffusion properties, particle size and permeability of the permeable colloidal particle can be investigated by phase-modulated fiber optic low-coherence dynamic light scattering.