Mi-term thesis Pauline ETIENNE

The remediation of contaminated soils and groundwater remains a critical environmental challenge. Diffusiophoresis, the migration of colloids driven by solute concentration gradients, offers a promising remediation pathway but is frequently overlooked in standard transport models for geological porous media. This study employs microfluidic devices that replicate natural porous media, enabling high-resolution visualization of colloidal trajectories. Experiments compare the behavior of micron-sized polystyrene particles under conditions with and without a stable salt gradient, using a dye tracer to visualize the gradient. The influence of local pore morphology and connectivity is systematically examined. Results demonstrate that chemical gradients significantly alter particle dynamics, notably enhancing mobility and directional persistence, even under substantial advective fluxes. Measurable deviations in particle trajectories induced by salt gradients underscore the critical role of diffusiophoresis. These findings highlight that diffusiophoresis must be considered to accurately predict colloid transport in heterogeneous pore structures, thereby complementing conventional purely hydrodynamic descriptions.