title: Sustaining reactivity of Fe(0) for nitrate reduction via electron transfer between dissolved Fe(2+) and surface iron oxides.
abstract: The mechanism of the effects of Fe(2+)(aq) on the reduction of NO3(-) by Fe(0) was investigated. The effects of initial pH on the rate of NO3(-) reduction and the Fe(0) surface characteristics revealed Fe(2+)(aq) and the characteristics of minerals on the surface of Fe(0) played an important role in NO3(-) reduction. Both NO3(-) reduction and the decrease of Fe(2+)(aq) exhibited similar kinetics and were promoted by each other. This promotion was associated with the types of the surface iron oxides of Fe(0). Additionally, further reduction of NO3(-) produced more surface iron oxides, supplying more active sites for Fe(2+)(aq), resulting in more electron transfer between Fe(2+) and surface iron oxides and a higher reaction rate. Using the isotope specificity of (57)Fe Mossbauer spectroscopy, it was verified that the Fe(2+)(aq) was continuously converted into Fe(3+) oxides on the surface of Fe(0) and then converted into Fe3O4 via electron transfer between Fe(2+) and the pre-existing surface Fe(3+) oxides. Electrochemistry measurements confirmed that the spontaneous electron transfer between the Fe(2+) and structural Fe(3+) species accelerated the interfacial electron transfer between the Fe species and NO3(-). This study provides a new insight into the interaction between Fe species and contaminants and interface electron transfer.
authors.affiliation: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Luchao
authors.initials: L
authors.lastname: Han
authors.affiliation: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Li
authors.initials: L
authors.lastname: yang
authors.affiliation: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Haibo
authors.initials: H
authors.lastname: Wang
authors.affiliation: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Xuexiang
authors.initials: X
authors.lastname: Hu
authors.affiliation: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China.
authors.forename: Zhan
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China. Electronic address: huchun@rcees.ac.cn.
authors.forename: Chun
authors.initials: C
authors.lastname: Hu
keywords: Ferrous iron; Interface electron transfer; Iron oxides; Zero-valent iron