Civil Engineering

 

Date of this Version

2003

Comments

Published in Published in J. Environ. Qual. 32:1306–1315 (2003). Copyright 2003. Used by permission.

Abstract

Under anoxic conditions, zerovalent iron (Fe0) reduces nitrate to and magnetite (Fe3O4) is produced at near-neutral pH. 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 reaction unless the system was augmented with Fe2+, Cu2+, or Al3+. Bathing the corroding Fe0 in a Fe2+ 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, nitrate reduction was not observed in the absence of Fe0. Nitrate removal was also enhanced by augmenting the Fe0–H2O system with Fe3+, Cu2+, or Al3+ but not Ca2+, Mg2+, or Zn2+. Our research indicates that a magnetite coating is not a hindrance to nitrate reduction by Fe0, provided sufficient aqueous Fe2+ is present in the system.

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