Fan Xiaomeng, Guan Xiaohong, Ma Jun, Ai Hengyu
School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin 150090, China.
J Environ Sci (China). 2009;21(8):1028-35. doi: 10.1016/s1001-0742(08)62378-5.
Although considerable research has been conducted on nitrate reduction by zero-valent iron powder (Fe0), these studies were mostly operated under anaerobic conditions with invariable pH that was unsuitable for practical application. Without reaction conditions (dissolved oxygen or reaction pH) control, this work aimed at subjecting the kinetics of denitrification by microscale Fe0 (160-200 mesh) to analysis the factors affecting the denitrification of nitrate and the composition of iron reductive products coating upon the iron surface. Results of the kinetics study have indicated that a higher initial concentration of nitrate would yield a greater reaction rate constant. The reduction rate of nitrate increased with increasing Fe0 dosage. The reaction can be described as a pseudo-first order reaction with respect to nitrate concentration or Fe0 dosage. Experimental results also suggested that nitrate reduction by microscale Fe0 without reaction condition control primarily was an acid-driven surface-mediated process, and the reaction order was 0.65 with respect to hydrogen ion concentration. The analyses of X-ray diffractometry and X-ray photoelectron spectroscopy indicated that a black coating, consisted of Fe2O3, Fe3O4 and FeO(OH), was formed on the surface of iron grains as an iron corrosion product when the system initial pH was lower than 5. The proportion of FeO(OH) increased as reaction time went on, whereas the proportion of Fe3O4 decreased.
尽管已经对零价铁粉（Fe0）还原硝酸盐进行了大量研究，但这些研究大多在厌氧条件下进行，pH值恒定，这不适用于实际应用。在没有反应条件（溶解氧或反应pH值）控制的情况下，这项工作旨在对微米级Fe0（160 - 200目）反硝化动力学进行分析，以研究影响硝酸盐反硝化的因素以及铁表面铁还原产物涂层的组成。动力学研究结果表明，较高的硝酸盐初始浓度会产生更大的反应速率常数。硝酸盐的还原速率随Fe0用量的增加而增加。该反应对于硝酸盐浓度或Fe0用量可描述为拟一级反应。实验结果还表明，在没有反应条件控制的情况下，微米级Fe0还原硝酸盐主要是一个酸驱动的表面介导过程，相对于氢离子浓度的反应级数为0.65。X射线衍射和X射线光电子能谱分析表明，当系统初始pH值低于5时，铁颗粒表面形成了由Fe2O3、Fe3O4和FeO(OH)组成的黑色涂层作为铁腐蚀产物。随着反应时间的延长，FeO(OH)的比例增加，而Fe3O4的比例降低。
