InterPore2026

Flow-Induced Surface Charge Heterogeneity and Its Impact on Cation Exchange Kinetics

22 May 2026, 09:50

15m

Oral Presentation (MS06) Interfacial phenomena across scales MS06

Speaker

Shahar Shahror (Soil and Water Sci. Faculty of Agriculture, Food and Environment, The Hebrew University of Jerusalem, Israel)

Description

Cation exchange, adsorption, and desorption kinetics at soil-water interfaces have been investigated for many years. Some experiments observed that the rate constant varies with flow conditions. This behavior is commonly attributed to transport limitations within the porous medium. However, recent work of Werkhoven et al. (2018) have shown that flow can induce strong lateral heterogeneity in surface charge and electrostatic potential within the electrical double layer (EDL), even on chemically homogeneous surfaces. Since ion exchange reaction are governed by the EDL, such flow dependent kinetics may originate from interfacial electrochemical processes rather than purely from transport constraints. In this study, we integrate electrostatics, fluid flow, and surface reactions using a Poisson-Nernst-Planck-Stokes framework. Extending the work of Werkhoven et al., we incorporate dynamic surface charge regulation and Stern-layer conductance and introduce a modified surface reaction scheme that explicitly represents cation exchange between Ca²⁺ and K⁺. Reaction parameters are taken from the classical adsorption and desorption measurements of Sparks et al. (1980). Simulations under imposed pressure gradients demonstrate that flow generates substantial lateral heterogeneity in surface charge and electrostatic potential. These results provide a mechanistic interpretation of Spark’s experimental observation that kinetic rate coefficients vary with flow conditions. The continued presence of lateral heterogeneity under the modified reaction kinetics indicates that flow-driven restructuring of the electrical double layer is an inherent characteristic of coupled electrokinetic systems. By explicitly elucidating the mechanisms through which fluid flow produces interfacial charge heterogeneity and alters reaction kinetics, this work establishes a mechanistic framework for linking hydrodynamic conditions with surface chemical processes in porous media.