Zeta potential changing in compressed clays

Abstract

Experimental results concerning the effect of loading pressure on the electrokinetic potential of kaolinite and montmorillonite particles in aqueous suspension are presented. It has been determined that the investigated suspensions of kaolinite and montmorillonite are aggregatively and sedimentally stable. The aggregative stability is evidenced by the calculated energy of the molecular motion (10–7–10–8 J/m2). The particle size monitoring indicates sedimentation stability. It was found that the change in the electrokinetic potential of clay particles depends on the loading pressure in different ways. Three classes were distinguished: 0–125 MPa, 150–750 MPa, 800–1200 MPa. In each class, changes in the electrokinetic potential are observed, due to the nature of the clay and the fractional composition. The fractional composition of the clay is also changed while compression. Pressure load has a different effect on the change in electrokinetic potential for kaolinite and montmorillonite. To establish the influence of the particle size distribution on the conditions of formation of the zeta potential on the surface of clay particles, a statistical correlation analysis was performed. It was established that for montmorillonite in the 1st and 2nd classes, the particle size distribution and zeta-potential have statistical correlations, and in 3rd class - not, whereas for kaolinite, statistical correlations between the particle size distribution and zeta potential are observed in the 1st and 3rd classes, and in the 2nd class - not. The resulting changes in the zeta potential are associated with the processes of dispersion and aggregation, which are implemented more intensively at low pressures (P < 150 MPa).

Keywords

• clay
• montmorillonite
• kaolinite
• clay particles
• zeta potential
• EDL
• pressure
• colloid
• mineral
• suspension
• structural bonds
• particle size analysis
• fraction
• correlation analysis
• engineering geology