Speaker
Description
Anomalous solute transport within porous media, characterized by early breakthrough and extended tailing in breakthrough curves, presents significant challenges for subsurface modeling. While existing models often emphasize geometrical and hydrodynamic factors, they tend to overlook non-Fickian diffusion mechanisms and viscosity effects during miscible displacement. This investigation explores the impact of non-Fickian diffusion, particularly the transport of H⁺ and OH⁻ ions responsible for pH equilibration, on the manifestation of anomalous transport behaviors. Microfluidic experiments were performed within homogeneous and heterogeneous porous media employing a dual-indicator methodology: Rhodamine 6G served as a conservative tracer to model mixing-induced transport phenomena, while Pyranine was utilized as a pH-sensitive dye to monitor real-time pH propagation. A basic solution displaced a slightly acidic water–glycerol mixture characterized by a tenfold viscosity difference. Transport mechanisms were analyzed using confocal microscopy, breakthrough curve analysis, pore volume assessments, and temporal spreading scaling under varied flow regimes.
Results indicate that actual pH transport consistently diverges from mixing-based predictions, showing suppressed anomalous behavior. Although predicted pH demonstrates pronounced viscous fingering and irregular fronts, the actual pH forms a stable central channel with improved displacement. Quantitatively, 95% breakthrough for actual pH occurs at substantially lower pore volumes than predicted (1.77 vs. 3.97 PV in homogeneous media; 5.00 vs. 8.14 PV in heterogeneous media), with temporal scaling confirming diminished anomalous transport. These findings elucidate that enhanced non-Fickian diffusion, propelled by the Grotthuss proton transport mechanism coupled with rapid acid–base neutralization, effectively mitigates heterogeneity-induced anomalous transport phenomena. This study contributes to a deeper comprehension of reactive transport processes in porous media and carries significant implications for applications such as enhanced oil recovery, carbon sequestration, and groundwater remediation.
| Country | Israel |
|---|---|
| Acceptance of the Terms & Conditions | Click here to agree |
