Aging of nanoscale zero valent iron (nZVI) in water leads to surface passivation, short reactive lifetime, and ultimately, loss of the zero-valent iron content. Sulfidation of nZVI (S-nZVI) has shown to alleviate some of these shortcomings by altering the surface composition to a sulfur based-coating, proving providing multiple advantages such as higher reaction rates and greater selectivity. This presentation will discuss field scale injection experiences where we injected S-nZVI stabilized with carboxyl methyl cellulose (CMC) to remediate a chlorinated hydrocarbon impacted site.  S-nZVI stabilized with CMC was quite mobile in permeable aquifer materials facilitating emplacement in the contaminated source zone for contaminant degradation.  S-nZVI led to significant decreases in contaminant mass as well as significant changes in contaminant distribution.  Changes in cVOCs concentrations and compound specific isotope analysis (CSIA) data suggest both sequential hydrogenolysis as well as reductive β-elimination as the possible transformation mechanisms during the short-term abiotic and long-term biotic dechlorination. One of the most positive outcomes of the CMC-S-nZVI field trial is the non-accumulation of lower chlorinated VOCs, particularly vinyl chloride, in comparison to previous nZVI field trials. Post-treatment soil cores also revealed significant decreases in cVOCs concentrations throughout the targeted treatment zones. Results from these studies suggest that S-nZVI has the potential to overcome many of the initial challenges limiting nZVI application.

Remediation using sulfidized nZVI (S-nZVI) a field trial

ACS Spring Meeting 2021

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