Some rheological and electrokinetic properties of kaolinite suspensions

Abstract

The rheological behaviour of kaolinite sols has been studied as a function of pH and in the presence of adsorbates. The Bingham yield value shows a pronounced maximum at about neutral pH due, it is suggested, to the presence of extended chains of particles attached together by electrostatic interactions between edges and faces, as has been suggested by Street. At high pH values the particles behave as individuals and the yield value can be very effectively correlated with the attractive and repulsive forces between them, using the basic notions of colloid stability theory. Adsorption of long-chain quaternary ammonium compounds on the clay surface at high pH enabled the particle interaction energy to be altered over a wide range and this adsorption itself allowed a study of the van der Waals interaction energy between the CH2 groups of the adsorbate; a value of 1.2kT was found for this latter energy, in excellent agreement with estimates based on micellization in solution.