Reactivity of Nitrate with Zero-Valent Iron

Katie M. Wagner, Tasios Karathanasis, Christopher J. Matocha

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Elevated nitrate concentrations in groundwater and surface water supplies can negatively impact the quality of the environment and human health. Recent studies have examined the use of zero-valent iron technology to treat nitrate-contaminated groundwater. Mechanistic aspects of nitrate reduction by zero-valent iron are unresolved. This project investigated the kinetics and mechanism of nitrate reduction by zero-valent iron under anoxic conditions and under oxic conditions. Stirred-batch reactions were studied over environmentally relevant ranges of reactant concentration, pH, and temperature. A complex rate expression was derived with a 1.8 order dependence on nitrate, a 1.4 order dependence on zero-valent iron, and a fractional order (0.8) dependence on proton concentrations under anoxic conditions. An apparent activation energy of 35 kJ mol−1 was observed indicating that nitrate reduction was diffusion controlled under our conditions. Furthermore, the calculated entropy of activation value of −162 J mol−1K−1 indicates that this reaction occurred by an associative mechanism. Under oxic conditions, there was a lag period in nitrate reduction where oxygen was preferentially utilized, leading to a slower rate of nitrate reduction when compared with anoxic conditions. These rate data can be used in predicting nitrate disappearance in nitrate-contaminated groundwater and wastewater treated with zero-valent iron.

Original languageEnglish
Article number2796
JournalWater (Switzerland)
Volume14
Issue number18
DOIs
StatePublished - Sep 2022

Bibliographical note

Funding Information:
This research was funded by National Research Initiative Competitive Grant no. 2002-35107-12214 from the USDA Cooperative State Research, Education, and Extension Service.

Publisher Copyright:
© 2022 by the authors.

Keywords

  • ammonium
  • kinetics
  • nitrate
  • nitrite
  • reduction
  • zero-valent iron

ASJC Scopus subject areas

  • Water Science and Technology
  • Geography, Planning and Development
  • Aquatic Science
  • Biochemistry

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