Towards the integration of electrochemical technologies for the remediation of low permeable soil polluted with volatile organic compounds

This study explores the interactions between ozone gas and soil for the remediation of low-permeability soils contaminated with trichlorobenzene, hexachlorocyclohexane, and xylene, and evaluates the synergistic effect of coupling ozonation with electrokinetic treatment. Ozone application alone achieved removal efficiencies exceeding 75% for trichlorobenzene and 87% for xylene, primarily through carboxylation and dichlorination pathways. Oxidant delivery emerged as a critical determinant of performance, with degradation rates highest near the injection zone. Soil moisture content strongly influenced efficacy: in dry soils, enhanced gas-phase propagation enabled TCB removals of up to 75%, whereas in humid soils, the removal rate achieved only 11%, likely due to limited mass transfer in saturated pores and ozone scavenging in the aqueous phase. Remarkably, integrating electrokinetics with ozonation produced a synergistic effect in VOC removal in humid soils, increasing from 2% (ozonation) to over 25% (hybrid remediation) after 4 h of treatment. This is driven by cathodic pH elevation and the generation of hydroxide ions, which accelerate ozone decomposition into species with enhanced reactivity to VOC. These species also propagate through electrochemically driven processes, increasing oxidant exposure. Our findings demonstrate a promising, environmentally friendly approach for treating soils contaminated with diverse VOCs, eliminating the need for harsh oxidant activators and expanding the applicability of ozonation in hybrid remediation strategies. • Ozonation removes VOCs in dry and humid soils. • Ozone delivery is strongly influenced by soil water content. • Dichlorination and carboxylation are the main removal mechanisms in ozonation • Combining electrokinetic remediation with ozonation yields higher removal of HCH in humid soils.