Variation of the electrokinetic parameters of colloidal systems

In this work, the surface charge of the particles, one of the most important properties of colloidal systems, was studied. The control of this parameter is the fundamental key to the stability of these systems. According to DLVO theory (Derjaguin & Landau, 1941; Verwey & Overbeek, 1948), high values of ζ-potential (±30mV) ensure greater electrostatic repulsion between particles, avoiding aggregation due to the attraction forces of van der Waals. The electrokinetic properties of montmorillonite clay (MC) were determined at different pHs, temperatures and electrolytes. The MC presented negative values of the ζ-potential in the range of pH 2-12 and 10-60 0C of temperature. High values of ζ-potential (-27-45mV), without isoelectric points, are characteristic of MC. The surface electric charge originates from the isomorphic substitutions of Al+3 for Mg+2 and/or Fe+2 in the octahedral sites and Si+4 for Al+3 in the tetrahedral sites of MC. The presence of electrolyte in the medium decreases the magnitude of the ζ -potential due to the compression of the EDL. If the dispersed ion is the potential determining ion (PDI), ζ-potential value will be controlled by the concentration of the PDI. Furthermore, the behavior of H-Size of particles, in different conditions, was studied and compared with Transmission Electron Microscope (TEM) analyzes. A charge distribution model around MC particles has been proposed.