Colloid adhesive parameters for chemically heterogeneous porous media

Area of Science:

• Environmental science
• Geochemistry
• Colloid and surface chemistry

Background:

• Colloid transport in porous media is crucial for environmental processes.
• Chemical heterogeneity of surfaces significantly impacts colloid adhesion.
• Existing models often simplify surface complexity, limiting accuracy.

Purpose of the Study:

• To develop a simple modeling approach for calculating colloid adhesive parameters in chemically heterogeneous porous media.
• To capture the influence of surface charge heterogeneity on colloid immobilization.
• To determine probability density functions (PDFs) for colloid adhesive parameters at the representative elementary area (REA) scale.

Main Methods:

• Discretized the zone of electrostatic influence (A(z)) into grid cells with varying zeta potentials.
• Calculated mean colloid adhesive parameters (zeta potential, interaction energy, sticking efficiency α, surface immobilization fraction S(f)).
• Utilized binomial mass distribution to calculate charge realization probabilities and derived PDFs for adhesive parameters.

Main Results:

• The model successfully calculated colloid adhesive parameters, including zeta potential, interaction energy, sticking efficiency (α), and immobilization fraction (S(f)).
• Validation against Monte Carlo simulations confirmed model accuracy for interaction energy distributions.
• Probability density functions (PDFs) of adhesive parameters at the REA scale were sensitive to colloid size, heterogeneity, grid cell properties, and ionic strength.

Conclusions:

• The developed model provides a simplified yet effective method for assessing colloid adhesion in complex porous environments.
• Understanding the sensitivity of adhesive parameters to various factors is key for predicting colloid behavior.
• This approach enhances the study of contaminant transport and geochemical processes in heterogeneous subsurface environments.