Catalytic dehydrochlorination of lindane by nitrogen-containing multiwalled carbon nanotubes (N-MWCNTs)

文献类型： 外文期刊

第一作者： Yang, Jirui

作者： Yang, Jirui;Shen, Feng;Qiu, Mo;Qi, Xinhua

作者机构：

关键词： Hexachlorocyclohexane;Lindane;Dehydrochlorination;Solid base;Nitrogen-containing multiwalled carbon nanotube

期刊名称：SCIENCE OF THE TOTAL ENVIRONMENT （ 影响因子：7.963； 五年影响因子：7.842 ）

ISSN： 0048-9697

年卷期： 2018 年 621 卷

页码：

收录情况： SCI

摘要： This paper reports a nonreductive dechlorination pathway (dehydrochlorination) of lindane in the presence of N-MWCNTs (CNT-N1 and CNT-N2) under environmentally relevant conditions. The enhanced catalytic dehydrochlorination at mild pH values (7.0-9.0) was mainly attributed to the Lewis base nature of nitrogen functional groups on the surface of N-MWCNTs, based on FT-IR spectra, X-ray photoelectron spectroscopy and CO2-TPD profile. Amine and pyridinic nitrogen species were inferred as the main basic sites that were responsible for the dehydrochlorination of lindane. The concentration of lindane was unchanged in homogenous alkaline aqueous solutions at pH 7.0 and 8.0 within 6 d, and up to 89.5% of lindane remained at pH 9.0. In sharp contrast, the reaction rate constant (k(obs)) increased from 0.024 to 0.876 d(-1) with the increasing pH from 7.0 to 9.0 when CNT-N2 catalyst was used. All lindane was transformed in the presence of CNT-N2 at pH 9.0, leading to a much greater k(obs) as compared to that obtained in homogenous solution (0.876 vs 0.019 d(-1)). Even at neutral pH condition, the k(obs) obtained in the presence of CNT-N2 was higher than that observed in weakly alkaline solution (0.024 d(-1) at pH 7.0 vs 0.019 d(-1) at pH 9.0). gamma-1,3,4,5,6-pentachlorocyclohexene and trichlorobenzene isomers were detected as the intermediate and final products, respectively. It might be inferred that amine and pyridinic nitrogen species could attack the hydrogen atom attached to the beta carbon, and the dehydrochlorination of lindane followed a beta-elimination mechanism. This study provides an alternative dechlorination way for making lindane less toxic and better biodegradable under mild conditions, which is beneficial for complete mineralization of lindane when coupled with microbial degradation. (c) 2017 Elsevier B.V. All rights reserved.

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