Zerovalent iron

Zerovalent iron (ZVI) describes forms of iron metal that are proposed for use in the environmental remediation of contaminated soil and groundwater.[1][2][3][4]

Model A
Model B
Click either image to enlarge

ZVI operates by electron transfer from Fe0 toward some organochlorine compounds, a common class of pollutants. The remediation process is proposed to generate Fe2+ and Cl− and halide-free organic products, all of which are relatively innocuous.[5] Nanoscale ZVIs (nZVIs) are commonly used in remediation of chlorinated compounds and other pollutants.[6]

Type of ZVI

  • Bulk Fe. Cast iron, consisting of scrap iron of construction grade, has been used as a reactive material for permeable reactive barriers (PRB) for groundwater remediation. Reactions are generally believed to occur on the Fe (oxide) surface; however, graphite inclusions can also serve as reaction sites.[7]
  • Nanoscale Fe. In addition to using macroscale iron in PRBs, nanoparticles (1-100 nm diameter) of zerovalent iron (nZVI) are effective.[2]
  • Zn. Zinc has shown 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.[8]

Type of contaminants treated

Treatment of many kinds of pollutants has been proposed, but few have been demonstrated in solving environmental challenges.

  • Cadmium (Cd2+) is converted to immobile Cd metal.[9]
  • Chloramines are effectively reduced by ZVI.[10]
  • Nitrate reduction by iron powder is observed at pH ≤ 4.[11] Ammonia is the end product. Using nanoscale iron, Nitrogen gas (N2) is the product.[12]
  • Nitrated aromatics are reduced by bulk iron.[7][13][14]
  • Chlorinated pesticides such as DDT, DDD, and DDE. The rates of dechlorination are enhanced by the surfactant Triton X-114.[15]
  • Perchloroethylene (PCE) and trichloroethylene (TCE), common industrial solvents, and their degradation products dichloroethylene (DCE) and vinyl chloride, can be reduced to ethylene and ethane using ZVI as a reagent. This can be applied to the remediation of soils contaminated with these chlorinated organic solvents, commonly found at dry cleaning facilities.[16]

Notes

  1. ^ Fu, Fenglian; Dionysiou, Dionysios D.; Liu, Hong (February 2014). "The use of zero-valent iron for groundwater remediation and wastewater treatment: A review". Journal of Hazardous Materials. 267: 194–205. Bibcode:2014JHzM..267..194F. doi:10.1016/j.jhazmat.2013.12.062. PMID 24457611.
  2. ^ a b Li, Xiao-qin; Elliott, Daniel W.; Zhang, Wei-xian (December 2006). "Zero-Valent Iron Nanoparticles for Abatement of Environmental Pollutants: Materials and Engineering Aspects". Critical Reviews in Solid State and Materials Sciences. 31 (4): 111–122. Bibcode:2006CRSSM..31..111L. doi:10.1080/10408430601057611.
  3. ^ Stefaniuk, Magdalena; Oleszczuk, Patryk; Ok, Yong Sik (March 2016). "Review on nano zerovalent iron (nZVI): From synthesis to environmental applications". Chemical Engineering Journal. 287: 618–632. Bibcode:2016ChEnJ.287..618S. doi:10.1016/j.cej.2015.11.046.
  4. ^ Gillham, Robert W.; Vogan, John; Gui, Lai; Duchene, Michael; Son, Jennifer (2010). "Iron Barrier Walls for Chlorinated Solvent Remediation". In Situ Remediation of Chlorinated Solvent Plumes. SERDP/ESTCP Environmental Remediation Technology. pp. 537–571. doi:10.1007/978-1-4419-1401-9_16. ISBN 978-1-4419-1400-2.
  5. ^ Tratnyek, Paul, and Rick Johnson. "Remediation with Iron Metal." Center for Groundwater Research. Oregon Health and Science University, 04 Feb. 2005.
  6. ^ Karn, Barbara; Kuiken, Todd; Otto, Martha (December 2009). "Nanotechnology and in Situ Remediation: A Review of the Benefits and Potential Risks". Environmental Health Perspectives. 117 (12): 1823–1831. Bibcode:2009EnvHP.117.1813K. doi:10.1289/ehp.0900793. PMC 2799454. PMID 20049198.
  7. ^ a b Jafarpour, Benham; Imhoff, Paul T.; Chiu, Pei C. (January 2005). "Quantification and modelling of 2,4-dinitrotoluene reduction with high-purity and cast iron". Journal of Contaminant Hydrology. 76 (1–2): 87–107. Bibcode:2005JCHyd..76...87J. doi:10.1016/j.jconhyd.2004.08.001. PMID 15588574.
  8. ^ Kim, Y-H.; Carraway, E. R. (December 2003). "Dechlorination of chlorinated phenols by zero valent zinc". Environmental Technology. 24 (12): 1455–1463. Bibcode:2003EnvTe..24.1455K. doi:10.1080/09593330309385690. PMID 14977141.
  9. ^ Boparai, Hardiljeet K.; Joseph, Meera; O’Carroll, Denis M. (February 2011). "Kinetics and thermodynamics of cadmium ion removal by adsorption onto nano zerovalent iron particles". Journal of Hazardous Materials. 186 (1): 458–465. Bibcode:2011JHzM..186..458B. doi:10.1016/j.jhazmat.2010.11.029. PMID 21130566.
  10. ^ Bedner, Mary; MacCrehan, William A; Helz, George R (May 2004). "Making chlorine greener: investigation of alternatives to sulfite for dechlorination". Water Research. 38 (10): 2505–2514. Bibcode:2004WatRe..38.2505B. doi:10.1016/j.watres.2004.03.010. PMID 15159154.
  11. ^ Huang, Chin-Pao; Wang, Hung-Wen; Chiu, Pei-Chun (August 1998). "Nitrate reduction by metallic iron". Water Research. 32 (8): 2257–2264. Bibcode:1998WatRe..32.2257H. doi:10.1016/S0043-1354(97)00464-8.
  12. ^ Choe, Seunghee; Chang, Yoon-Young; Hwang, Kyung-Yub; Khim, Jeehyeong (October 2000). "Kinetics of reductive denitrification by nanoscale zero-valent iron". Chemosphere. 41 (8): 1307–1311. Bibcode:2000Chmsp..41.1307C. doi:10.1016/S0045-6535(99)00506-8. PMID 10901263.
  13. ^ "2,4-DIAMINOTOLUENE". Organic Syntheses. 11: 32. 1931. doi:10.15227/orgsyn.011.0032.
  14. ^ "o-Aminobenzaldehyde, Redox-Neutral Aminal Formation and Synthesis of Deoxyvasicinone". Organic Syntheses. 89: 274. 2012. doi:10.15227/orgsyn.089.0274.
  15. ^ Sayles, Gregory D.; You, Guanrong; Wang, Maoxiu; Kupferle, Margaret J. (December 1997). "DDT, DDD, and DDE Dechlorination by Zero-Valent Iron". Environmental Science & Technology. 31 (12): 3448–3454. Bibcode:1997EnST...31.3448S. doi:10.1021/es9701669.
  16. ^ Navarra, Wanda; Sacco, Olga; Rescigno, Raffaella; Daniel, Christophe; Vaiano, Vincenzo; Pisano, Domenico; Brancato, Bruno; Casertano, Francesco; Raiola, Mario; Venditto, Vincenzo (July 2023). "Remediation of perchloroethylene contaminated groundwater using Fe0/ZnS embedded in a highly porous polymer: Experimental results on pilot-scale photoreactor and kinetic modeling analysis for industrial scale-up". Catalysis Communications. 180 106699. doi:10.1016/j.catcom.2023.106699.

Further reading

  • Tratnyek, Paul (2003). "Permeable Reactive Barriers of Iron and Other Zero-Valent Metals". In Tarr, Matthew A. (ed.). Chemical Degradation Methods for Wastes and Pollutants. Environmental Science & Pollution. Vol. 26. pp. 371–421. doi:10.1201/9780203912553. ISBN 978-0-8247-4307-9.
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