Sulfidation of ZVI by mechanochemical synthesis: Lattice doping and enhanced reactivity.

Sulfur doping into the crystalline lattice of zero-valent iron (ZVI) enhances its electronic properties and local structure, improving its efficacy for transforming environmental contaminants. This study demonstrates a novel high-energy ball milling approach to initiate mechanochemical reactions for precise sulfur doping into the Fe0 lattice, addressing the hazards posed by hexavalent chromium (Cr(VI)) and trichloroethylene (TCE), two priority pollutants known to threaten public health and ecosystems. Mechanochemically sulfidized ZVI (SZVI, 0.182 %-5.698 % sulfur) exhibited Cr(VI) and TCE removal rates up to 20 and 7 times higher, respectively, than SZVI prepared by conventional solution chemistry with aqueous Na2S, forming primarily surface-bound iron sulfides. By tuning milling time to control sulfur incorporation, removal capacities of 130.5 mg/g for Cr(VI) (S: 3.802 %) and 70.1 mg/g for TCE (S: 4.557 %) were achieved under environmentally relevant conditions mimicking groundwater matrices. Mechanical energy catalyzes in-situ iron sulfide (FeSx) ieformation through lattice expansion and atomic-scale Fe-S interpenetration, as confirmed by FeS and FeS2 crystalline phases, symmetric Fe-S bond vibrations, and rearrangement in the Fe coordination environment. These findings advance ZVI-based remediation strategies, mitigating risks from hazardous contaminants in environmental systems.