Experimental Quantification of the Electro-Osmotic Flow Field in an Irregular Porous Medium and Its Consequences for Dewatering.

The development of dewatering methods driven by electric fields offers significant potential to reduce the energy demand for these processes. Electro-osmotic dewatering relies on the application of an electric field across a porous matrix possessing a surface charge, inducing liquid transport through electrokinetic mechanisms. While the feasibility and energy efficiency of electro-osmotic dewatering have been demonstrated, a fundamental understanding of how the irregular, porous microstructure affects the uniformity of dewatering is lacking. In this work, we investigate electro-osmotic flow in porous media micromodels and directly compare it with conventional pressure-driven flow under controlled experimental conditions. The micromodel is designed and microfabricated to exhibit a controlled, heterogeneous microstructure. Pore-scale velocity fields are measured by using particle tracking velocimetry and characterized through velocity probability density functions. A multiphysics model, coupling ion transport, electrostatics, and hydrodynamics, is validated against the experiments. The results show that, in contrast to pressure-driven flow, which exhibits broader velocity distributions with preferential flow paths and stagnant regions, electro-osmotic flow produces a narrower velocity distribution, even in heterogeneous porous structures. These findings demonstrate the potential of electro-osmotic dewatering to achieve more uniform water removal in low-permeability materials and provide a predictive framework for optimizing electrically driven dewatering.