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Effects of Oxide Coating and Selected Cations on Nitrate Reduction by Iron Metal
Author(s) -
Huang Yong H.,
Zhang Tian C.,
Shea Patrick J.,
Comfort Steve D.
Publication year - 2003
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2003.1306
Subject(s) - nitrate , metal , coating , oxide , reduction (mathematics) , inorganic chemistry , iron oxide , chemistry , environmental chemistry , organic chemistry , mathematics , geometry
Under anoxic conditions, zerovalent iron (Fe 0 ) reduces nitrate to ammonium and magnetite (Fe 3 O 4 ) is produced at near‐neutral pH. Nitrate removal was most rapid at low pH (2–4); however, the formation of a black oxide film at pH 5 to 8 temporarily halted or slowed the reaction unless the system was augmented with Fe 2+ , Cu 2+ , or Al 3+ Bathing the corroding Fe 0 in a Fe 2+ solution greatly enhanced nitrate reduction at near‐neutral pH and coincided with the formation of a black precipitate. X‐ray diffractometry and scanning electron microscopy confirmed that both the black precipitate and black oxide coating on the iron surface were magnetite. In this system, ferrous iron was determined to be a partial contributor to nitrate removal, but nitrate reduction was not observed in the absence of Fe 0 Nitrate removal was also enhanced by augmenting the Fe 0 –H 2 O system with Fe 3+ , Cu 2+ , or Al 3+ but not Ca 2+ , Mg 2+ , or Zn 2+ Our research indicates that a magnetite coating is not a hindrance to nitrate reduction by Fe 0 , provided sufficient aqueous Fe 2+ is present in the system.