Oxidative degradation kinetics and products of chlortetracycline by manganese dioxide

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• 作者：Gao  ; Chen^a ;   ; ^b ;   ; ¹ ; Ling  ; Zhao^a ;   ; ^b ;   ; ^{zhaoling@issas.ac.cn} ; Yuan-hua  ; Dong^a ;   ; ^b
• 关键词：Abiotic degradation ; Chlortetracycline ; ¦Ä-MnO₂ ; Kinetics ; Products
• 刊名：Journal of Hazardous Materials
• 出版年：2011
• 出版时间：15 October 2011
• 年：2011
• 卷：193
• 期：Complete
• 页码：128-138
• 全文大小：907 K

文摘

This study investigated the abiotic transformation kinetics of chlortetracycline (CTC) by synthesized ¦Ä-MnO₂ under conditions of different solutions. CTC was rapidly oxidized by ¦Ä-MnO₂, with the generation of Mn²⁺. The measured CTC transformation rate increased considerably with an increase in initial ¦Ä-MnO₂ concentration but it decreased as the initial CTC concentration increased. Both the measured CTC transformation rate and the amount of Mn²⁺ generated decreased with increasing pH. The CTC transformation rate rose with an increase in temperature. The apparent activation energy (45 ¡À 14 kJ mol^?) was consistent with a surface-controlled reaction. Dissolved Mn²⁺ and Zn²⁺, as background cations, and substituted phenols, as co-solutes, remarkably decreased the transformation rate of CTC. Liquid chromatography¨Ctandem mass spectrometry (LC¨CMS-MS) was used to identify oxidation products, which include iso-CTC, 4-epi-CTC, anhydro-CTC and 4-epi-anhydro-CTC, keto-CTC, 4-epi-keto-CTC, N-demethyl-CTC, 4-epi-N-demethyl-CTC, N-didemethyl-CTC and 4-epi-N-didemethyl-CTC. Product identification together with Fourier transform-infrared (FTIR) spectra suggested that the hydroxyl groups at C6 and C12 and the dimethylamine group of CTC reacted with the Mn¨COH groups on the ¦Ä-MnO₂ surface. Thus, ¦Ä-MnO₂ in the soils most probably plays an important role in the abiotic transformation of tetracycline antibiotics.