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Chemical Reduction of Nitrate by Zero-Valent Iron: Shrinking-Core versus Surface Kinetics Models

Department of Chemical Engineering, University of Malaga, 29071 Malaga, Spain
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Int. J. Environ. Res. Public Health 2020, 17(4), 1241; https://doi.org/10.3390/ijerph17041241
Received: 18 January 2020 / Revised: 3 February 2020 / Accepted: 12 February 2020 / Published: 14 February 2020
(This article belongs to the Special Issue Environmental Remediation of Soils and Groundwater)
Zero valent iron (ZVI) is being used in permeable reactive barriers (PRB) for the removal of oxidant contaminants, from nitrate to chlorinated organics. A sound design of these barriers requires a good understanding of kinetics. Here we present a study of the kinetics of nitrate reduction under relatively low values of pH, from 2 to 4.5. We use a particle size of 0.42 mm, which is within the recommended size for PRBs (0.2 mm to 2.0 mm). In order to avoid possible mass-transfer limitations, a well-stirred reactor coupled with a fluidized bed reactor was used. The experiments were performed at constant pH values using a pH controller that allows to accurately track the amount of acid added. Since the reduction of H + to H 2 by the oxidation of ZVI will always be present for these pH values, blank experiments (without nitrate) were performed and the rate of this H + reduction obtained. This rate of reduction was studied using three kinetic models: a regular empirical one, the Shrinking-Core Model (SCM), and the Surface Kinetics Model (SKM). The best performance was obtained from the SKM model. Therefore, this model was also used to study the results for the nitrate reduction, also with satisfactory results. In both cases, some assumptions are introduced to maintain a moderate number of fitting parameters. View Full-Text
Keywords: nitrate reduction; zero valent iron; permeable reactive barrier; shrinking-core model nitrate reduction; zero valent iron; permeable reactive barrier; shrinking-core model
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Villen-Guzman, M.; Paz-Garcia, J.M.; Arhoun, B.; Cerrillo-Gonzalez, M.M.; Rodriguez-Maroto, J.M.; Vereda-Alonso, C.; Gomez-Lahoz, C. Chemical Reduction of Nitrate by Zero-Valent Iron: Shrinking-Core versus Surface Kinetics Models. Int. J. Environ. Res. Public Health 2020, 17, 1241.

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