Pore-scale optimization of H2O2-based TCE remediation using stabilizer-enhanced oxidant delivery and follow-up water injection.

Hydrogen peroxide (H2O2)-based in situ chemical oxidation (ISCO) is a commonly applied technique for remediating groundwater contaminated by dense non-aqueous phase liquids (DNAPL) such as trichloroethylene (TCE). However, the overall remediation efficiency is often constrained by oxidant self-decomposition and gas-induced pore blockage, which hinder oxidant accessibility to contaminants. To improve the remediation performance, this study experimentally investigated three optimization strategies: follow-up water injection, chemical stabilization, and staged oxidant injection. These three strategies aim to remobilize trapped phases and restore oxidant access, directly suppress H2O2 self-decomposition by introducing a stabilizer, and reintroduce fresh oxidant to reboot the oxidation process, respectively. The pore-scale remediation processes were visualized using time-resolved three-dimensional micro-computed tomography (3D micro-CT) to quantify the spatial and temporal evolution of TCE and gas phases in porous media. Results show that the combined strategy of follow-up water injection and stabilizer achieved a significant enhancement in overall TCE remediation under 5 wt% H2O2 condition, obtaining the highest TCE removal of 78.7%. This study provides direct mechanistic evidence of how physical and chemical measures can jointly enhance oxidant delivery during the remediation process. The pore-scale insights offer guidance for optimizing oxidant management and injection strategies in groundwater environments, and highlight the need to consider gas-liquid-DNAPL interactions when designing field-scale remediation systems.