Kinetics of Nitrite Reduction by Zinc Metal: Influence of Metal Shape on the Determination of Kinetic Parameters

Heterogeneous chemical reactions are complicated, especially in the case of competitive reactions. The aim of this study was to investigate the elimination of nitrite (NO(2)(-)) by applying a metallic reduction using zero-valent zinc (Zn(0)). The effect of pH, stirring, and metal shape (powder and chips) on the rate and products of nitrite reduction were studied in a batch-stirred reactor. The obtained data have been used to optimize the conditions for metallic reduction of NO(2)(-) and for kinetic parameters identification. It was found that the dissolution of zinc involves a pseudo-first-order reaction independent of the shape of the metal. Further, the influence of operating conditions on nitrogen (N(2)) and ammonium (NH(4)(+)) formation has been determined. It was found that a decrease in pH and in the Zn(0) content enhances NH(4)(+) production. If kinetic parameters can be approximated easily for constant surface area, it was demonstrated that surface evolution had to be integrated for metal powder. Finally, a numerical simulation has been used to determine the kinetic parameters for NO(2)(-) reduction with zinc powder. Water Environ. Res., 82, 648 (2010).