Zero-valent iron (ZVI), as bulk shavings or colloidal nanoparticles and used as-is or attached to various supports, is one of the most widely used engineering materials for <i>in situ</i> groundwater remediation. In spite of iron’s versatile utility in treating a broad range of reducible contaminants, the degradation rates of chlorinated ethenes, an important class of groundwater contaminants, by ZVI is relatively slow in the absence of metal catalysts, and the surface of ZVI is prone to passivation in groundwater environment.  Previous studies have shown that ZVI nanoparticles synthesized in the presence of reduced sulfur compounds possess increased reactivity towards chlorinated ethenes and other contaminants. Recent findings by our group suggest that surface conditioning with sulfide precursors is a general approach to enhance iron reactivity and is applicable to different forms or sources of ZVI. In this presentation, the kinetics and pathways of trichloroethene degradation are investigated in representative groundwater matrices. The stability of the modified ZVI in air and aqueous environment are examined and the role of sulfur in the iron substrate is proposed based on surface chemistry and compound-specific isotope analyses.

Surface conditioning of ZVI for enhanced dechlorination reactivity and material stability

251st National Meeting (2016)

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