Department of Civil and Environmental Engineering, Korea Advanced Institute of Science and Technology, Yuseong-gu, Daejeon 305-701, South Korea.
Water Sci Technol. 2010;61(3):705-12. doi: 10.2166/wst.2010.895.
This study investigates the fate of nitrogen species during nitrate reduction by nanoscale zero valent iron (NZVI) as well as the related kinetics. The NZVI used for the experiments was prepared by chemical reduction without a stabilizing agent. The pseudo first order kinetic constant of nitrate reduction at 30 degrees C with an NZVI/nitrate ratio of 1.25:1, which were the reference conditions of this study, was 4.08 h(-1) (R(2)=0.955). A nitrogen mass balance was established by quantitative analysis of aqueous-phase and gas-phase nitrogen species. The results confirm that the nitrate was converted to ammonium ion, that ammonia stripping subsequently occurred under a strong alkaline condition, and that the total amount of aqueous nitrogen was consequently reduced. The nitrate reduction rate also increased with a lower pH and a higher temperature when microscale ZVI was used. However, in contrast to the reaction by microscale ZVI, the nitrate reduction rate by NZVI was higher for an unbuffered condition, possibly due to the abundance of surface atoms and the smaller size.
本研究考察了纳米零价铁（NZVI）还原硝酸盐过程中氮物种的归宿以及相关动力学。用于实验的 NZVI 通过无稳定剂的化学还原法制备。在 30°C 下，当 NZVI/硝酸盐的比例为 1.25:1 时，硝酸盐还原的拟一级动力学常数为 4.08 h(-1)（R(2)=0.955）。通过定量分析水相和气相氮物种建立了氮质量平衡。结果证实，硝酸盐被转化为铵离子，在强碱性条件下随后发生氨吹脱，因此水相氮的总量减少。当使用微尺度 ZVI 时，硝酸盐还原速率也随较低的 pH 值和较高的温度而增加。然而，与微尺度 ZVI 的反应相反，在无缓冲条件下，NZVI 的硝酸盐还原速率更高，这可能是由于表面原子的丰富和较小的尺寸所致。
