不同阳离子对Fe^0还原硝酸盐的影响

Effect of different cations on nitrate reduction by zero-valent iron

由于水中硝酸盐污染的普遍性、难去除性和对人体健康的潜在危害性而引起人们的广泛关注。通过批实验,考察了不同阳离子(Fe2+、Fe3+和Cu2+)对Fe0还原硝酸盐的影响。结果表明,由于加入阳离子可直接或间接地增加溶液中的Fe2+而都能促进硝酸盐的还原,作用顺序为Fe3+>Fe2+>Cu2+;Fe2+对硝酸盐的还原具有重要作用,并随着反应的进行,转化为铁氧化物附着在铁表面而降低铁的活性;硝酸盐还原的主要产物为氨氮,亚硝酸盐只在反应初期有少量积累,尤其是加Cu2+的体系中,但随后都很快降低;在所有体系中,检测到的三氮(NO3--N、NO2--N和NH4+-N)之和只占理论总氮的51.5%~82.6%;动力学分析表明,硝酸盐的还原在不加阳离子的体系中更符合一级反应,而加了阳离子的处理更符合Lo-gistic模型。本研究结果阐明了Fe2+对Fe0还原硝酸盐的重要性。

Since nitrate contamination in water is very universal, hard removal and potential harm to people,it attracts extensive attention. Batch tests were conducted to investigate the effects of cation（Fe2＋ , Fe3＋ and Cu2＋ ） on nitrate reduction by zero-valent iron （ Fe0） . The results demonstrated that three cations significantly accelerated nitrate reduction in the order Fe3＋ 〉 Fe2＋ 〉 Cu2＋ , because they increased ferrous ion in the solution directly or indirectly. Ferrous ion was very important for nitrate reduction and converted to iron oxides covered on the surface of iron grains, which decreased the reactivity of Fe0. Ammonia was the major end-product of nitrate reduction. Nitrite accumulated in the original period of reaction, especially in the system added Cu2＋, but subsequently it decreased rapidly. In the all systems containing Fe0, the sum of three nitrogen （ NOa-N, NO2-N and NH4＋ -N） determinated in solution was only 51.5% - 82.6% comparing with theoretic total nitrogen. Kinetics analysis revealed that the denitrification reaction without adding cation appeared to be a pseudofirst-order model, but it was consistent with logistic model when cation was introduced. The research may lead to understand the importance of Fe2＋ for nitrate reduction by Fe0.