THERMODYNAMIC PROPERTIES OF THE S/L INTERFACIAL LAYER - STABILIZATION OF THE COLLOIDAL SYSTEM IN BINARY LIQUIDS

In the knowledge of the adsorption and wetting properties of solid particles the influence of particle-liquid and interparticle interaction has been examined on the stability and structure formation of suspensions obtained for hydrophobic SiO2 colloids in the mixtures benzene+n-heptane and methanol+benzene. The Hamaker constants of the adsorption layer of composition range. The Hamaker constant have been determined by optical dispersion measurements in the entire mixture composition range. The Hamaker constant of the adsorption layer of composition different from that in the bulk have been calculated at several mixture compositions on the basis of the adsorption results. Having the excess isotherms available enabled us to determine the adsorption layer thickness as a function of the bulk composition. For interparticle attractive potentials, model calculations have been effected on the basis of the Vincent model. In the case of hydrophobic particles dispersed in benzene+n-heptane and methanol+benzene mixtures it was established that the change of the attractive potential was in accordance with the interactions obtained from rheological measurements.