Correlation between the Structural-Activity of Sulfidated Nanoscale Zerovalent Iron and its Enhanced Reactivity for Cr(Vi) Reduction

Abstract

Sulfidation has gained increasing attention due to its merits to improve the structural-activity and thus enhance reactivity of nanoscale zerovalent iron (nZVI). While few studies have been conducted to elucidate the relationship between the structural-activity and reactivity of nZVI, which is important for up-scaling such a decontamination strategy. Herein, taking chromate (Cr(VI)) as the targeting contaminant, we found that the reactivity of nZVI toward Cr(VI) could be enhanced by sulfidation to varying extents. The reaction rates of sulfidated nZVI (S-nZVI) for Cr(VI) removal were 10.3-27.3 folds greater than that of nZVI. In addition, sulfidation enhanced the electronic conductivity of nZVI by forming conductive iron sulfides (FeSx), while simultaneously reducing particle aggregation and thus attenuating settling rate of nZVI in water. More importantly, the decontamination reactivity of S-nZVI exhibited a negative correlation with its sedimentation activity and electrical conductivity. These relationships can be potentially used to predict the decontamination reactivity of S-nZVI if its sedimentation or conductivity activity was known in advance. Finally, this study clarified the sulfidation-induced improvement in reactivity of nZVI toward Cr(VI), which should be primarily associated with the improved reactive site of S-nZVI due to excellent dispersion and excellent conductivity due to FeSx introduction, ultimately facilitating the reduction of Cr(VI) by nZVI. In general, this research identified quantitative relationships of S-nZVI based on its reactivity and structural-activity, which will provide important theoretical foundations and methodological guidance for the groundwater remediation by nZVI-based technology.

Keywords: nanoscale zerovalent iron, sulfidation, structural-activity, redox reduction, correlation analysis