EFFECTS OF INTERPARTICLE INTERACTIONS ON STABILITY, AGGREGATION AND SEDIMENTATION IN COLLOIDAL SUSPENSIONS

Relations between interparticle effective interactions, structure form ation, stability and sedimentation for a colloidal system are presente d in this paper. For a binary mixture of large and small particles, th e potential of mean forces between large particles is obtained from th e Orenstein-Zernicke equation. We incorporated the small particles in our numerical simulations by using this potential of the mean force as the interparticle effective interaction. Our numerical results reveal the phenomenon of strong particle aggregation due to the attractive d epletion force exerted by small particles. In the absence of the effec t of gravity, this aggregation can result in flocculation and the form ation of particle clusters thereby forming ''void'' structures, while under the influence of gravity, the aggregation can greatly affect the sedimentation rates. An analytical expression relating the aggregatio n number to the sedimentation velocity is presented. Our sedimentation experiments with a bidisperse latex suspension as well as clay partic le dispersions show both the destabilizing and stabilizing effects of small particles, which are in qualitative agreement with our theoretic al predictions.