Reduction of aqueous perchlorate by iron surfaces in batch and column studies
Abstract
The rate and extent of perchlorate reduction on several types of iron metal was studied in batch and column reactors. Mass balances performed on the batch experiments indicate that perchlorate is reduced to chloride. Perchlorate reduction was proportional to the iron dosage in the batch reactors, with up to 66 percent removal in the highest dosage system. Surface normalized reaction rates among three commercial sources of iron filings were very similar for acid washed samples. The most significant perchlorate transformation occurred in solutions with near neutral initial pH values. Surface mediation of the reaction is supported by the absence of reduction in batch experiments with soluble Fe(II). Elevated chloride concentrations significantly inhibited perchlorate reduction, and lower removal rates were observed for iron samples with higher amounts of background chloride contamination. Perchlorate reduction was not observed on electrolytic sources of iron or on a pure mixed phase oxide (Fe2O3), suggesting that the reactive iron phase is not pure zero valent iron but is instead a combination of the elemental metal coated by a mixed valence iron hydr(oxide) phase. The observed reaction rates are too slow for direct use in remediation system design, but the findings may provide a basis for future development of cost-effective abiotic perchlorate reduction techniques. Further work to elucidate the mechanism of perchlorate reduction on iron media is in progress.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.H61C0816M
- Keywords:
-
- 1806 Chemistry of fresh water;
- 1829 Groundwater hydrology;
- 1899 General or miscellaneous