Huang Yong H, Zhang Tian C
Department of Civil Engineering, University of Nebraska-Lincoln at Omaha Campus, Omaha, NE 68182-0178, USA.
Chemosphere. 2006 Aug;64(6):937-43. doi: 10.1016/j.chemosphere.2006.01.025. Epub 2006 Feb 20.
Batch tests were conducted to investigate nitrite reduction in a zerovalent iron (Fe0) system under various conditions. Nitrite at 1.4 mM initial concentration was slowly reduced to nitrogen gas in the first stage (days 1-6), which was mediated by an amorphous, Fe(II)-rich iron oxide coating. The second stage (days 7-14) featured a rapid reduction of nitrite to both ammonia and nitrogen gas and the formation of a more crystalline, magnetite form iron oxide coating. Water reduction by Fe0 occurred concurrently with nitrite reduction from the beginning and contributed significantly to the overall iron corrosion. Nitrite at 14 mM was found to passivate the surface of Fe0 grains with respect to nitrite reduction. Adding aqueous Fe2+ significantly accelerated reduction of nitrite by Fe0 to nitrogen gas with lepidocrocite as the main iron corrosion product. Substantially, though still substoichiometrically, 0.55 mol of Fe2+ were concomitantly consumed per 1.0 mol nitrite reduction, indicating that Fe0 was the main electron source. In the presence of Fe2+, nitrite reduction out-competed water reduction in terms of contributing to the overall iron corrosion. Results of this study help understand complicated interactions between water reduction and nitrite reduction, the roles of surface-bound Fe2+, and the evolution of the iron corrosion coating.
进行了批次试验，以研究在各种条件下零价铁（Fe0）系统中硝酸盐的还原情况。初始浓度为1.4 mM的亚硝酸盐在第一阶段（第1 - 6天）缓慢还原为氮气，这是由富含Fe(II)的无定形铁氧化物涂层介导的。第二阶段（第7 - 14天）的特点是亚硝酸盐迅速还原为氨和氮气，并形成更结晶的磁铁矿形式的铁氧化物涂层。从一开始，Fe0对水的还原就与亚硝酸盐的还原同时发生，并对整体铁腐蚀有显著贡献。发现14 mM的亚硝酸盐相对于亚硝酸盐还原会使Fe0颗粒表面钝化。添加Fe2+水溶液显著加速了Fe0将亚硝酸盐还原为氮气的过程，主要的铁腐蚀产物是纤铁矿。基本上，尽管仍未达到化学计量比，但每还原1.0 mol亚硝酸盐会伴随消耗0.55 mol Fe2+，这表明Fe0是主要的电子来源。在存在Fe2+的情况下，就对整体铁腐蚀的贡献而言，亚硝酸盐还原比水还原更具竞争力。本研究结果有助于理解水还原和亚硝酸盐还原之间的复杂相互作用、表面结合的Fe2+的作用以及铁腐蚀涂层的演变。
