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Article

Reactivity of Nitrate with Zero-Valent Iron

1
Salt Lake County Extension, Utah State University, Salt Lake City, UT 84190, USA
2
Plant and Soil Sciences, University of Kentucky, Lexington, KY 40546, USA
*
Author to whom correspondence should be addressed.
Academic Editor: Shejiang Liu
Water 2022, 14(18), 2796; https://doi.org/10.3390/w14182796
Received: 15 July 2022 / Revised: 30 August 2022 / Accepted: 31 August 2022 / Published: 8 September 2022
(This article belongs to the Special Issue Control and Remediation of Contaminants in Soil and Groundwater)
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. View Full-Text
Keywords: kinetics; nitrate; nitrite; ammonium; zero-valent iron; reduction kinetics; nitrate; nitrite; ammonium; zero-valent iron; reduction
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MDPI and ACS Style

Wagner, K.M.; Karathanasis, T.; Matocha, C.J. Reactivity of Nitrate with Zero-Valent Iron. Water 2022, 14, 2796. https://doi.org/10.3390/w14182796

AMA Style

Wagner KM, Karathanasis T, Matocha CJ. Reactivity of Nitrate with Zero-Valent Iron. Water. 2022; 14(18):2796. https://doi.org/10.3390/w14182796

Chicago/Turabian Style

Wagner, Katie M., Tasios Karathanasis, and Christopher J. Matocha. 2022. "Reactivity of Nitrate with Zero-Valent Iron" Water 14, no. 18: 2796. https://doi.org/10.3390/w14182796

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