Unusual Yield Stress Behavior of Kaolin Clay Slurries

  • Mr Jeremy Teo, The University of Western Australia, Australia
  • Ms EJen Teh, The University of Western Australia, Australia
  • Prof Yee-Kwong Leong, The University of Western Australia, Australia
  • Prof Andy Fourie, The University of Western Australia, Australia
  • Prof Martin Fahey, The University of Western Australia, Australia

    • The Unimin’s kaolin clay slurries exhibited a very unusual relationship between its rheology and surface chemistry. It displayed a maximum yield stress that is not located at the point of zero or low zeta potential. The yield stress-DLVO force model that predicts a linear relationship between yield stress and square of zeta potential with a negative slope, is obeyed by other kaolin slurries [Hunter and Nicol, JCIS 28 (1968) 250]. However with this kaolin slurry three linear relationships with negative and positive slopes were observed. The negative slope relationships were observed to occur at the low and high zeta potential regions. In the intermediate zeta potential region, the slope is positive. In the presence of adequate amount of adsorbed polyphosphates, the linear region at the medium and high zeta potential regions disappeared. Heterogeneous charge or electrostatic attraction between clay platelets were proposed to explain the maximum yield stress and the disappearance of this yield stress in the presence of adsorbed polyphosphate.