Effects of Sulfidation and Nitrate on the Reduction of N-Nitrosodimethylamine by Zerovalent Iron
Effects of Sulfidation and Nitrate on the Reduction of N-Nitrosodimethylamine by Zerovalent Iron
复制标题
硫化物和硝酸盐对零价铁还原N-亚硝基二甲胺的影响
DOI：
10.1021/acs.est.9b02419
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发表时间：
2019
影响因子：
11.4
通讯作者：
Tratnyek Paul G.
中科院分区：
文献类型：
--
作者：
Qin Hejie;Guan Xiaohong;Tratnyek Paul G.
地下水和废水中的氧化性物种之间竞争零价铁（ZVI）的还原能力，使ZVI的目标污染物降解的选择性超过其他还原途径的ZVI为基础的水处理工艺的可行性的一个主要决定因素。通过硫化，减少污染物超过水的选择性得到改善，但硫化对其他竞争反应的影响尚不清楚。使用N-亚硝基二甲胺（NDMA）作为目标污染物、硝酸盐作为共污染物以及有和没有硫化的微米级ZVI来研究这些竞争反应之间的相互作用。未硫化的ZVI通过N，N-二甲基肼将NDMA还原为二甲胺，但硝酸盐的加入降低了NDMA还原的速率并增加了观察到的中间体的量。与硫化ZVI，NDMA还原的动力学和产品与未硫化ZVI的那些相似，但没有观察到硝酸盐的抑制作用。相反，硝酸盐的减少，这占主导地位的NDMA减少在非硫化ZVI系统，强烈抑制硫化。H2和Fe 2+的产生几乎不受硝酸盐浓度的影响。因此，硫化主要通过抑制硝酸盐还原来提高ZVI还原NDMA的效率。硫化时，ZVI对NDMA的选择性超过硝酸盐的选择性的转变是由于FeS取代了Fe 0/FexOy表面位点。
Competition among oxidizing species in groundwater and wastewater for the reductive capacity of zerovalent iron (ZVI) makes the selectivity of ZVI for target contaminant degradation over other reduction pathways a major determinant of the feasibility of ZVI-based water treatment processes. The selectivity for reduction of contaminants over water is improved by sulfidation, but the effect of sulfidation on other competing reactions is not known. The interaction between these competing reactions was investigated usingN-nitrosodimethylamine (NDMA) as the target contaminant, nitrate as a co-contaminant, and micrometer-sized ZVI with and without sulfidation. Unsulfidated ZVI reduced NDMA to dimethylamine viaN,N-dimethylhydrazine, but the addition of nitrate decreased the rate of NDMA reduction and increased the quantity of intermediate observed. With sulfidated ZVI, the kinetics and products of NDMA reduction were similar to those with unsulfidated ZVI, but no inhibitory effect of nitrate was observed. Conversely, the reduction of nitrate—which dominated NDMA reduction in unsulfidated ZVI systems—was strongly inhibited by sulfidation. H2and Fe2+generation by sulfidated ZVI was almost independent of nitrate concentration. Therefore, sulfidation improved the efficiency of NDMA reduction by ZVI in the presence of nitrate mainly by inhibiting nitrate reduction. The shift in selectivity of ZVI for NDMA over nitrate upon sulfidation was due to replacement of Fe0/FexOysurface sites with FeS.