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Zerovalent iron (ZVI) is jargon that describes forms of iron metal used for
*Bulk Fe.
Zerovalent iron (ZVI) is jargon that describes forms of iron metal used for Groundwater remediation
Groundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the sub ...
. ZVI serves as a reducing agent.Gillham, Robert, John Vogan, Lai Gui, Michael Duchene, and Jennifer Son. "Iron Barrier Walls for Chlorinated Solvent Remediation." ''In Situ'' Remediation of Chlorinated Solvent Plumes. Ed. Hans F. Stroo and C. Herb Ward. New York, NY: Springer Science+Business Media, 2010.
ZVI operates by electron transfer
Electron transfer (ET) occurs when an electron relocates from an atom or molecule to another such chemical entity. ET is a mechanistic description of certain kinds of redox reactions involving transfer of electrons.
Electrochemical processes ar ...
from Fe0 to the pollutant. For organochlorine pollutants, Fe2+ and Cl− are produced.Tratnyek, Paul, and Rick Johnson. "Remediation with Iron Metal." Center for Groundwater Research. Oregon Health and Science University, 04 Feb. 2005.
Type of metal
*Bulk Fe. Cast iron
Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...
, consisting of scrap iron of construction grade, has been used as a reactive material for permeable reactive barriers for groundwater remediation
Groundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the sub ...
. Reactions are generally believed to occur on the Fe (oxide) surface; however, graphite inclusions have been shown can also serve as a reaction sites.Jafarpour, B.; Imhoff, P. T.; Chiu. P.C. 2005. Quantification and modeling of 2,4-dinitrotoluene reduction with high-purity and cast iron. Journal of Contaminant Hydrology. 76(1-2): 87-107.
*Nanoscale Fe. In addition to using macroscale iron in PRBs, nanoparticles (1-100 nm diameter) of zerovalent iron (nZVI) are effective.
*Zn. Zinc has showed much higher reactivity toward pentachlorophenol than iron. This indicates that zinc may be used as a replacement for ZVI in dechlorinating chlorinated phenols. Chlorinated phenols are sequentially dechlorinated and thus less chlorinated phenols have been identified as a reduction product.Kim, Y. H.; Carraway, E. R. 2003. Dechlorination of chlorinated phenols by zerovalent zinc. Environmental Technology. 24(12): 1455-1463.
Type of contaminants treated
*Cadmium
Cadmium is a chemical element with the symbol Cd and atomic number 48. This soft, silvery-white metal is chemically similar to the two other stable metals in group 12, zinc and mercury. Like zinc, it demonstrates oxidation state +2 in most of ...
(Cd2+) is converted to immobile Cd metal.
*Chloramines
Chloramines refer to derivatives of ammonia and organic amines wherein one or more N-H bonds have been replaced by N-Cl bonds. Two classes of compounds are considered: inorganic chloramines and organic chloramines.
Inorganic chloramines
Inorgan ...
are effectively reduced by ZVI.Bedner, M.; W. A. MacCrehan; G. R. Helz. 2004. Making chlorine greener: investigation of alternatives to sulfite for dechlorination. Water Research. 38(10): 2505-2514.
*nitrate
Nitrate is a polyatomic ion
A polyatomic ion, also known as a molecular ion, is a covalent bonded set of two or more atoms, or of a metal complex, that can be considered to behave as a single unit and that has a net charge that is not zer ...
reduction by iron powder is observed only at pH≤4.Huang, C.; Wang, H.; Chiu, P. 1998. Nitrate reduction by metallic iron. Water Research. 32(8): 2257-2264. Ammonia is the end product. Using nanoscale iron N2 gas is the product.Choe, S.; Chang, Y.; Hwang, K.; Khim, J. 1999. Kinetics of reductive denitrification by nanoscale zerovalent iron. Chemosphere. 41(8): 1307-1311.
*Nitrated aromatics are reduced by bulk iron.
*Chlorinated pesticides such as DDT
Dichlorodiphenyltrichloroethane, commonly known as DDT, is a colorless, tasteless, and almost odorless crystalline chemical compound, an organochloride. Originally developed as an insecticide, it became infamous for its environmental impacts. ...
, DDD, and DDE. The rates of dechlorination are enhanced by the surfactant (Triton X-114).Sayles, G. D.; You, G.; Wang, M.; Kupferle, M. J. 1997. DDT, DDD, and DDE dechlorination by zerovalent iron. Environmental Science & Technology. 31(12): 3448-3454.
Further reading
*Tratnyek, P. G.; M. M. Scherer; T. J. Johnson; Matheson, L.J. (2003). Permeable reactive barriers of iron and other zerovalent metals. In: Tarr M. A. (ed.), Chemical Degradation Methods for Wastes and Pollutants; Environmental and Industrial Applications. Environmental Science and Pollution Control, Marcel Dekker, New York, pp 371–421.Notes
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