Effective kinetics and phases saturation impact on surface reactions in porous media

Coupling of unsaturated flows and surface reactions, including sorption and desorption, takes place in environmental contexts such as soils and the unsaturated zone. Lower sorption coefficients than those observed from batch experiments are found in natural soils. However, a deep understanding of this coupling is missing. To achieve this objective, we designed microfluidics experiments and performed direct numerical simulations based on experimental images at the microscale. We explore the effects of fluid flow dynamics and reaction kinetics on the effective kinetics. We have observed that an increase in the air volume within the porous medium promotes more heterogeneous fluid flow velocities, controlling the mixing of the transported reactant and resulting in a non-monotonic effective kinetic of the surface reaction.