Key soil physicochemical properties affecting the dechlorination activity of sulfurized zero-valent iron: Different roles of soil particles and soluble components.

Sulfurized zero-valent iron (SZVI) is a promising material for controlling soil/groundwater halogenated hydrocarbon pollution. However, systematic studies on how various physicochemical properties of soil affect SZVI dechlorination activity are still lacking. To explore the influence of solid and soluble components on SZVI activity, this study compared the dechlorination performance of SZVI on trichloroethylene (TCE) in three different soils across five systems: SZVIwater (aqueous solution system), SZVIsoil (soil system), SZVIpre-soil (pre-adsorbed TCE soil system), SZVIex (soil extract system), and SZVIde-soil (soil system without soluble components). Additionally, the SZVI activity before and after aging in soil extract and solutions of various soluble components (within the concentration range of the soil extract) was compared, and the mechanism by which key soluble components influence the SZVI activity was explored. Results indicated that the dechlorination activity of SZVI was higher in soils compared to the performance in aqueous solution, and high soil organic matter content was the key inhibitor. The influence of soil solid-phase components on SZVI activity was significantly greater than that of soluble components. Soil particles enhanced SZVI activity by providing effective contact sites between SZVI and TCE, whereas soluble components inhibited SZVI activity by altering the physicochemical properties of its surface (e.g., NO3- and PO43-) and competing with TCE for electrons during the reaction (e.g., NO3- and Mn2+). These findings offer new critical insights for selecting and optimizing materials based on soil physicochemical properties.