Rheo-optics of concentrated kaolinite suspensions

A shear-optical method is described which uses multiply scattered light to investigate concentrated colloidal kaolinite suspensions. The shear-optical response derives from the orientation of floc fragments or discrete colloidal particles in the flowing suspension. The apparatus required is robust and inexpensive. The method is used to study the effect of pH, and an organic deflocculant, on the flocculation of kaolinite. The effect of pH on the shear-optical response of concentrated suspensions correlates inversely with the pH-dependence of the fractal dimension measured by Herrington and Midmore for kaolinite flocs in very dilute suspensions. The effect of deflocculant on the shear-optical response correlates closely with the effect of the same deflocculant on the suspension viscosity.