Bimolecular Reactive Transport Experiments and Simulations in Porous Media

Abstract

For reactive transport process in porous media, limited mixing and non-Fickian behavior are difficult to understand and predict. To explore the effects of anomalous diffusion and limited mixing, the column-based experiments of bimolecular reactive migration were performed and simulated by the CTRW-FEM model (continuous time random walk-finite element method). Simulated parameters were calibrated and the correlation coefficients between modeled and observed BTCs (breakthrough curves) were greater than 0.9, indicating that CTRW-FEM can solve over-prediction and tailing problems effectively. Porous media with coarser particle size show enhanced mixing and the non-Fickian behavior is not affected by particle size. β (a parameter of CTRW-FEM) and Da (Damköhler number) of CTRW-FEM under different Pe (Péclet number) values showed logarithmic linear relationship. Model sensitivity analysis of the CTRW-FEM model show that the peak concentration is most sensitive to the average pore velocity and the arriving peak time of peak concentration is most sensitive to β. These findings provide a theoretical basis for handling mixing and non-Fickian behavior patterns under actual environmental conditions.