Insights into asphaltene aggregation in the Na-montmorillonite interlayer.

Area of Science:

• Environmental Science
• Geochemistry
• Materials Science

Background:

• Asphaltenes, heavy fractions of crude oil, pose environmental challenges due to their persistence.
• Understanding asphaltene behavior in geological formations like Na-montmorillonite (MMT) is crucial for remediation.

Purpose of the Study:

• To investigate the diffusion and aggregation of asphaltenes within MMT interlayers under varying conditions.
• To elucidate the influence of water saturation, salinity, interlayer space, and humic substances on asphaltene transport.

Main Methods:

• Molecular dynamic simulations were employed to determine molecular configuration, density profiles, diffusion coefficients, and aggregation intensity.
• Atomic force microscopy was used to characterize the 3D topography and particle size of asphaltene aggregates.

Main Results:

• Asphaltene diffusivity was significantly higher in fresh water compared to saline water (35‰), though salinity minimally affected aggregation.
• Reduced pore water content and MMT interlayer space markedly decreased asphaltene mobility.
• Humic substances led to co-aggregation and sequestration of asphaltenes, reducing diffusion by an order of magnitude and increasing aggregation by 33%.

Conclusions:

• Humic substances play a critical role in immobilizing asphaltenes within MMT interlayers.
• Findings provide insights into the fate and transport of heavy oil residues in contaminated soils, aiding environmental risk assessment.