About Zero Valent Iron (ZVI)
The Zero Valent Iron (ZVI; aka iron powders) can be used as an effective amendment with various in-situ technologies to treat groundwater and soils contaminated with a wide variety of volatile organic compounds (VOCs; Table 1). A typical in-situ configuration consists of ZVI being placed in “hot-spot” areas, plume areas or as a barrier across the flow path of a VOC. ZVI can initiate several chemical reactions in which VOCs are destroyed to non-toxic end products.
Advantages:
- Cost Effective
- Long-Term Treatment
- Sustainable/Green
- Destroys Contaminants with no Toxic End-product
The corrosion of ZVI (Fe(0)) produces both ferrous iron and hydrogen that are reducing agents for contaminants VOCs. The degradation process is an abiotic reductive dehalogenation process that occurs on the surface of the granular iron, with the iron acting as an electron source (Figure 2). Pathway A shows a direct electron transfer to the adsorbed halocarbon (RX) at the metal-water interface, resulting in dechlorination and production of Fe(II). Pathway B shows that Fe(II) resulting from corrosion of Fe(0) may also dechlorinate RX, thereby producing Fe(III). Pathway C shows that H2 from the anaerobic corrosion of Fe(II) might react with RX if an effective catalyst is present. For more discussion see Matheson and Tratnyek (1994) Environ. Sci. Technol. 28(12): 2045-2053.
The ZVI technology is applicable in most geochemical conditions and does not require frequent reapplications, resulting in a reliable, long-term treatment solution.
ZVI is Effective on the Following Compounds:
| Tetrachloroethene (PCE) | Chloroethane |
| Trichloroethene (TCE) | Carbon Tetrachloride (CT) |
| cis 1,2-Dichloroethene (cDCE) | Trichloromethane (TCM) |
| trans 1,2-Dichloroethene (tDCE) | Dichloromethane (DCM) |
| 1,1-Dichloroethene (11DCE) | Chloromethane |
| Vinyl Chloride (VC) | Tribromomethane (TBM) |
| Hexachloroethane (HCA) | 1,2-Dibromoethane (1,2-EDB) |
| 1,1,2,2-Tetrachloroethane | Trichlorotrifluoroethane (Freon 113) |
| 1,1,1,2-Tetrachloroethane | Trichlorofluoromethane (Freon 11) |
| 1,1,1-Trichloroethane | 1,2,3-Trichloropropane (123TCP) |
| 1,1,2-Trichloroethane | 1,2-Dichloropropane (12DCP) |
| 1,1-Dichloroethane | Lindane |
| 1,2-Dichloroethane (1,2-DCA) | Hexachlorobutadiene (HCBD) |
| N-nitrosodimethylamine (NDMA) | Trichloropropane |
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Figure 1: Three Simple Reductive Mechanisms
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Feroxsm (Zero Valent Iron)
ARS' patented Feroxsm (US Patent No. #5975798) technology is an in-situ remediation process for the treatment of chlorinated hydrocarbons, PCBs and heavy metals. The FeroxSM process involves the subsurface injection and dispersion of a highly reactive zero-valent iron (ZVI) powder into the saturated zones of contaminated sites. In-situ reductive dechlorination using ZVI has been extensively studied in the form of permeable reaction walls or funnel-and-gate systems. However, these passive systems are designed to treat the dissolved phase compounds that migrate within the groundwater and do not address adsorbed insoluble contaminants (source zone contaminants) typically bound to the soils. A key component of the Feroxsm process is the fact that the target contaminant has greater direct contact with the highly dispersed injected iron powder. ARS' expertise in subsurface injections and fracturing provides a unique method of emplacing the iron into the subsurface by directly accessing and remediating the leachable and adsorbed contaminants in the soil or rock matrix. A significant and inherent advantage of the Feroxsm process is the flexibility of the injection process to strategically emplace the iron powder or create surgical “spot” injections according to the contaminant distribution and geological heterogeneities present in the subsurface.
Figure 3: Conformational Boring Shown ZVI Emplacement By Feroxsm Process (85-88 ft. bgs. 17 ft)
Feroxsm Applicability
The combination of our proprietary zero-valent iron powder and our gas-based injection methods have propelled Feroxsm to the forefront of in-situ remediation technologies. It is a powerful tool when dealing with difficult geologies or contaminants. When coupled with Pneumatic Fracturing, Feroxsm can be s point and allows for sufficient mixing of the Feroxsm within the soil matrix.
The Feroxsm process has been commercially applied at more than 25 sites in the United States and specified as the technology in six ROD.
Latest News
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July 1, 2010 - Hepure Completes Bulk Delivery of Emulsified Vegetable Oil For Bioremediation at Former Air Force Facility in California
Hepure and Terra Systems Inc. recently teamed to provide almost 210,000 lbs of Terra Systems' highly regarded Slow Release Substrate (SRS™) for anaerobic bioremediation at a former Air Force facility in California. Hepure was able to meet the client’s needs by custom blending on a "just-in-time" basis and providing bulk delivery of SRS™ in 5,000 gallon tanks. Hepure is the exclusive distributor of Terra Systems' industry-leading line of products for enhanced bioremediation.
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