A methodical comparative analysis of the improved dechlorination of trichloroethylene (TCE) using C-, N-, and S-modified zero-valent iron (ZVI)

Zero-valent iron (ZVI) technology is regarded as one of the most efficient approaches for remediating groundwater contaminated with chlorinated hydrocarbons (CHCs). Despite its highly reactive nature, the corrosion of ZVI in aqueous solution readily results in surface passivation, which diminishes its reactivity. ZVI doped with heteroatoms such as carbon (C), nitrogen (N), and sulfur (S) has displayed excellent performance in trichloroethylene (TCE) degradation. Nevertheless, the effects of these heteroatoms on ZVI materials, along with their various degradation mechanisms, remains ambiguous. In this study, C-mZVI^bm, N-mZVI^bm, and S-mZVI^bm were prepared, respectively, via a mechanochemical method and utilized for TCE degradation. The dechlorination reaction facilitated by each material was thoroughly investigated both theoretically and experimentally, focusing on TCE adsorption affinity, the dechlorination process, hydrogen evolution reaction (HER), electron efficiency, and lifetime. Among the three materials, S-mZVI^bm exhibited 100% TCE removal in less than 24 h., as well as improved electron efficiency and lifetime, primarily attributed to its high TCE adsorption energy and the suppression of HER. These integrated theoretical and experimental results indicate that S-mZVI^bm nanoparticles are a promising and innovative material for in situ groundwater TCE remediation.