Multiscale Insights into Structure-Porosity Interplay and Water Adsorption in Granular Activated Carbon for Enhanced Electrochemical Water Treatment

Abstract

Granular activated carbon (GAC) has proven to be a highly effective material for electrochemical water treatment due to its large surface area and porous structure. This study presents a multiscale investigation combining molecular dynamics (MD) simulations, continuum-scale modeling, and experimental validation to understand how the GAC structure influences water adsorption and reactivity. MD simulations show that highly porous GAC (porosity up to 0.55) adsorbs up to 1.2 kg of water per kg of carbon, with an adsorption energy reaching 880 kJ/kg. Continuum modeling using the coupled level-set volume-of-fluid (CLSVOF) method demonstrates that high-porosity GAC reduces surface blockage by promoting bubble mobility. Experimental results confirm these findings: unpressed GAC electrodes (i.e., larger porosity) with a lower density (∼0.1997 g/cm3) generated up to 180 ppm of hydroxyl radicals, compared to 100 ppm from pressed electrodes with equal mass. These findings indicate that optimizing GAC porosity and particle size enhances both water transport and reactive oxygen species (ROS) generation, hence improving the treatment performance. This integrated modeling and experimental framework highlight structure-function relationships in GAC electrodes and inform the design of scalable, high-efficiency systems. This work focuses on water interactions with GAC, opening doors for future studies on pollutant-specific reactivity in the electrochemical water treatment system.