Tuning mZVI surface species through synergistic Sulfur-Graphite incorporation via Mechanochemistry technique for High-Efficiency TCE Dechloridation and electron utilization

Abstract

Zero-valent iron (ZVI) technology has gained significant attention for the in situ dechlorination of trichloroethylene (TCE), a typical organic pollutant commonly found in soils and groundwater. However, ZVI technology faces several critical challenges, such as insufficient reactivity, easy passivation, limited selectivity, and unclear mechanisms. In this study, a ball-milled S&C-mZVI^bm material was synthesized by co-incorporation strategy and demonstrated a significant improvement in the degradation efficiency of ZVI. This enhancement occurs alongside a reduction in the hydrogen evolution reaction (HER), thereby increasing the electron selectivity during TCE dechlorination. Through comprehensive characterization techniques, we have shown that the co-incorporation of carbon and sulfur into mZVI results in improved affinity for TCE, accelerated electron transfer, and reduced charge-transfer resistances. The S&C-mZVI^bm also exhibited excellent long-term stability, with degradation efficiency higher than 90% even after 12 repeated cycles. The pathway for TCE dichlorination can be precisely adjusted by the S addition, i.e., the addition of S simultaneously promoted the acetylene production by β-elimination and DCEs production by hydrogenolysis, while suppressed the acetylene transformation to other hydrocarbon products. These findings not only advance the development of ZVI-based materials but also broaden their applicability in the remediation of groundwater contaminated with chlorinated hydrocarbons.