Probing Anisotropic Surface Properties of Illite by Atomic Force Microscopy

Area of Science:

• Colloid and Surface Science
• Mineral Processing
• Geochemistry

Background:

• Understanding illite's surface charge is crucial for mineral processing and oil sands extraction.
• Direct measurement of illite's surface potentials at edge and basal planes is lacking.

Purpose of the Study:

• To investigate the surface charging properties of illite's edge and basal surfaces.
• To determine the surface potentials of illite edge and basal surfaces using direct force measurements.

Main Methods:

• Utilized atomic force microscopy (AFM) to measure interaction forces between probes and illite surfaces.
• Employed Derjaguin-Landau-Verwey-Overbeek (DLVO) theory to analyze measured forces and derive surface potentials.
• Conducted experiments across a pH range of 3.0 to 10.0 in 10 mM KCl solutions.

Main Results:

• Illite basal and edge surfaces are negatively charged across the studied pH range.
• The basal surface exhibited more negative charges than the edge surface from pH 3.0 to 10.0.
• The point of zero charge (PZC) for the edge surface was estimated to be below pH 3.0, while no PZC was detected for the basal surface.

Conclusions:

• This research provides the first direct measurement of separate surface potentials for illite edge and basal surfaces.
• Findings offer critical insights into the colloidal behavior of illite in mineral processing and oil sands extraction.
• Surface charge characteristics significantly influence illite's behavior in industrial applications.