Abiotic reactions with iron-sulfur minerals have shown potential for contaminant transformation. Previous studies have explored the influence of Fe:S ratios, pH, and ligand availability on iron sulfide reactivity for organic pollutant transformation in groundwater, but further research is necessary to understand the role of biogenic sulfide production and different iron sources on iron sulfide reactivity. This work explores the transformation of trichloroethylene (TCE) to acetylene in the presence of sulfate reducing bacteria (SRB) and iron, as either ferrihydrite or aqueous ferrous iron (Fe<sup>2+</sup>). In anaerobic, pH-controlled batch experiments, SRB were grown with lactate as the electron donor and sulfate as the electron acceptor, and iron was introduced as either ferrihydrite or Fe<sup>2+</sup>. TCE was added to batch experiments after aging, and acetylene production was measured over time using GC-FID. Aqueous iron and sulfur species were determined initially, after aging, and after reaction with TCE.  After terminating experiments, the iron-sulfur solids were characterized using XRD, XPS, and SEM. This data was used to interpret the redox transformations of iron and sulfur during reaction from TCE to acetylene. Initial ferrihydrite experiments showed that increasing the Fe:S ratio from 2:1 to 20:1 results in more efficient acetylene production, but an Fe:S ratio of 50:1 shows a decrease in acetylene production. The results of this work will contribute to the development of improved technologies focused on in situ transformation of organic contaminants as well as improved natural attenuation models. This research also lays the groundwork for future experiments focused on iron-sulfide precipitation and TCE transformation in diffusion-limited, heterogeneous environments.

Contributions of iron and biological sulfate reduction to abiotic transformation of organic groundwater contaminants

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.