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Reduction of Nitrogen-Oxygen Containing Contaminants (NOCs) in Aquatic Environments

项目来源

美国国家科学基金(NSF)

项目主持人

Huichun Zhang

项目受资助机构

TEMPLE UNIVERSITY

项目编号

1507981

立项年度

2015

立项时间

未公开

研究期限

未知 / 未知

项目级别

国家级

受资助金额

300000.00美元

学科

未公开

学科代码

未公开

基金类别

Standard Grant

关键词

Environmental Chemical Science ; Sustainable Chemistry

参与者

未公开

参与机构

未公开

项目标书摘要：With this award,the Environmental Chemical Sciences Program of the Division of Chemistry is funding Professor Huichun J.Zhang of Temple University to examine the nitrogen-oxygen single bond(N-O)as a reducible functional group toward reductive transformations under environmental conditions.The introduction of N-O containing contaminants(NOCs)into aquatic environments is an important emerging water issue.This project aims to develop accurate environmental risk assessment of NOCs and to develop advanced technologies to effectively treat NOCs contaminated water and sites.The findings are expected to help guide the chemical industry to design more environmentally-friendly chemical products.The project is expected to broaden participation from underrepresented minorities and women in environmental chemistry/engineering and to provide training for future scientists and engineers in this cross-disciplinary area.This project focuses on examining reduction kinetics and mechanisms of a diverse range of NOCs by soluble Fe(II)species through a combination of experimental and theoretical approaches.Advanced experimental approaches,including kinetic,electrochemical cell,isotopic,spectroscopic and chromatographic approaches,are to be conducted to elucidate key elementary steps in NOC reductions,such as protonation,complexation,electron transfer and N-O bond cleavage.The most likely rate-limiting step of each subset of NOCs is to be identified by characterizing all of the stationary points in the relevant elementary steps along the reaction pathway.Molecular descriptors are being computed to develop quantitative structure-activity relationships so as to provide the community with quantifiable and experimentally grounded numbers that pertain to the susceptibility of N-O bonds to reductive cleavage in the environment.

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  • 1.Experimental and Computational Evidence for the Reduction Mechanisms of Aromatic N-oxides by Aqueous Fe-II-Tiron Complex

    • 关键词：
    • Electron transitions;Aromatic compounds;Computation theory;Iron compounds;Reduction;Chemical bonds;Electron transport properties;Isotopes;Chains;Protonation ;Density functional theory;Electron transfer;Electron transfer process;Elementary reaction;Kinetic isotope effects;Rate-limiting steps;Reduction mechanisms;Solvent isotope effects;Theoretical approach
    • Chen, Yiling;Dong, Hao;Zhang, Huichun
    • 《Environmental Science and Technology》
    • 2016年
    • 50卷
    • 1期
    • 期刊

    A combined experimental-theoretical approach was taken to elucidate the reduction mechanisms of five representative aromatic N-oxides (ANOs) by FeII-tiron complex and to identify the rate-limiting step. Based on the possible types of complexes formed with the reductant, three groups of ANOs were studied: type I refers to those forming 5-membered ring complexes through the N and O atoms on the side chain; type II refers to those forming 6-membered ring complexes through the N-oxide O atom and the O atom on the side chain; and type III refers to complexation through the N-oxide O atom only. Density functional theory calculations suggested that the elementary reactions, including protonation, N-O bond cleavage, and the second electron transfer processes, are barrierless, indicating that the first electron transfer is rate-limiting. Consistent with the theoretical results, the experimental solvent isotope effect, KIEH, for the reduction of quinoline N-oxide (a type III ANO) was obtained to be 1.072 ± 0.025, suggesting protonation was not involved in the rate-limiting step. The measured nitrogen kinetic isotope effect, KIEN, for the reduction of pyridine N-oxide (a type III ANO) (1.022 ± 0.006) is in good agreement with the calculated KIEN for its first electron transfer (1.011-1.028), confirming that the first electron transfer is rate-limiting. Electrochemical cell experiments demonstrated that the electron transfer process can be facilitated significantly by type I complexation with FeL26- (1:2 FeII-tiron complex), to some extent by type II complexation with free FeII, but not by weak type III complexation. © 2015 American Chemical Society.

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