Mapping and Quantifying Surface Charges on Clay Nanoparticles.

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Environmental Engineering

Background:

• Clay nanoparticles are critical in oil sands processing, influencing bitumen extraction and tailings sedimentation.
• Understanding their electrical properties, specifically surface charge, is essential for process optimization.
• Mature fine tailings (MFT) management is a significant environmental challenge in the oil industry.

Purpose of the Study:

• To directly map and quantify the surface charges on clay nanoparticles.
• To compare the surface charge characteristics of clean kaolinite with clay particles from oil sands tailings.
• To investigate the influence of bituminous compounds on the surface charge of tailings clays.

Main Methods:

• Utilized Kelvin probe force microscopy (KPFM) for surface potential mapping.
• Employed electrostatic force microscopy (EFM) for quantitative surface charge density measurements.
• Analyzed the morphology and surface potential of clean kaolinite and tailings-derived clay nanoparticles.

Main Results:

• Clean kaolinite nanoparticles exhibit a layered structure with layer-dependent surface potential.
• A surface charge density of 25 nC/cm² was determined for clean kaolinite layers.
• Clay particles from tailings showed a reduced surface charge density of 7 nC/cm², likely due to adsorbed bituminous compounds.

Conclusions:

• Direct quantification of clay nanoparticle surface charge is achievable using KPFM and EFM.
• Adsorption of bituminous compounds significantly reduces the surface charge of clay particles in oil sands tailings.
• These findings provide crucial insights into the behavior of clays in oil sands processing and MFT.