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.

Background: Electrohydrodynamic (EHD) drying relies on the generation of a corona wind that is created with a high electric potential between an emitter and a ground electrode. The impinging corona wind enhances convective heat and mass transport close to the sample, which is positioned on the ground electrode. Although EHD drying is reported to have large potential for milder and energy efficient drying, most studies have only evaluated its potential at the lab scale and for specific applications. Scope and approach: This review focusses on discussing the underlying physical phenomena that may be expected to influence the performance of EHD drying processes. Specifically, we discuss how corona wind changes due to discharge behaviour as it is influenced by moisture release during drying, how the microstructural properties of the product could influence electromigration in the drying material and how EHD drying could be efficiently and safely scaled up for biobased & food products. We conclude with an outlook to the research that still is required to concretize the potential of EHD drying in practice. Key findings and conclusions: In EHD drying, electrical discharge induces airflow which enhances external convective drying. Studies coupling physical phenomena are still lacking, although some possible couplings are mentioned in chapter 2. Internal mass transfer is enhanced due to presence of an electrical potential over the product, which can cause several electrically-driven transport phenomena as discussed in chapter 3. Several drying setups have been explored in industry, of which the characteristics are summarized in chapter 4.