Fate of nitrogen species in nitrate reduction by nanoscale zero valent iron and characterization of the reaction kinetics

摘要

This study investigates the fate of nitrogen species during nitrate reduction by nanoscale zeronvalent iron (NZVI) as well as the related kinetics. The NZVI used for the experiments was preparednby chemical reduction without a stabilizing agent. The pseudo first order kinetic constant ofnnitrate reduction at 308C with an NZVIitrate ratio of 1.25:1, which were the reference conditionsnof this study, was 4.08 h21 (R 2 ?0.955). A nitrogen mass balance was established by quantitativenanalysis of aqueous-phase and gas-phase nitrogen species. The results confirm that the nitratenwas converted to ammonium ion, that ammonia stripping subsequently occurred under a strongnalkaline condition, and that the total amount of aqueous nitrogen was consequently reduced.nThe nitrate reduction rate also increased with a lower pH and a higher temperature whennmicroscale ZVI was used. However, in contrast to the reaction by microscale ZVI, the nitratenreduction rate by NZVI was higher for an unbuffered condition, possibly due to the abundancenof surface atoms and the smaller size.