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

Maria Villen-Guzman, Juan Manuel Paz-Garcia, Brahim Arhoun, Maria del Mar Cerrillo-Gonzalez, Jose Miguel Rodriguez-Maroto, Carlos Vereda-Alonso and Cesar Gomez-Lahoz
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Maria Villen-Guzman: Department of Chemical Engineering, University of Malaga, 29071 Malaga, Spain
Juan Manuel Paz-Garcia: Department of Chemical Engineering, University of Malaga, 29071 Malaga, Spain
Brahim Arhoun: Department of Chemical Engineering, University of Malaga, 29071 Malaga, Spain
Maria del Mar Cerrillo-Gonzalez: Department of Chemical Engineering, University of Malaga, 29071 Malaga, Spain
Jose Miguel Rodriguez-Maroto: Department of Chemical Engineering, University of Malaga, 29071 Malaga, Spain
Carlos Vereda-Alonso: Department of Chemical Engineering, University of Malaga, 29071 Malaga, Spain
Cesar Gomez-Lahoz: Department of Chemical Engineering, University of Malaga, 29071 Malaga, Spain

IJERPH, 2020, vol. 17, issue 4, 1-16

Abstract: 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.

Keywords: nitrate reduction; zero valent iron; permeable reactive barrier; shrinking-core model (search for similar items in EconPapers)
JEL-codes: I I1 I3 Q Q5 (search for similar items in EconPapers)
Date: 2020
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