Microwave-enhanced H2O2-based process for treating aqueous malachite green solutions: intermediates and degradation mechanism.
This work was originally performed to compare H(2)O(2)-based degradation of aqueous malachite green (MG) under microwave (MW)-enhanced and conventional heating (CH)-enhanced conditions, with the whole reaction courses traced by UV-vis spectrophotometer. The results showed that the higher discoloration rates of MG were available during MW-enhanced process, implying that the special heating way of MW might be more benefit for the generation of hydroxyl radicals than that of CH. Furthermore, major intermediates were separated and identified by HPLC-ESI-MS and GC-MS techniques. On the basis of 53 intermediates, degradation mechanism was deduced as follows: firstly, N-de-methylation reactions. Secondly, adduction reactions. Thirdly, decomposition of conjugated structure reactions of MG. Fourthly, removal of benzene reactions. Finally, open-ring reactions. Additionally, results revealed that microwave-enhanced H(2)O(2)-based treatment had more advantages, such as higher degradation efficiency, and no removal of catalyst after treatment.
Ju
Yongming
Y
State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, PR China.
Yang
Shaogui
S
Ding
Youchao
Y
Sun
Cheng
C
Gu
Chenggang
C
He
Zhong
Z
Qin
Chao
C
He
Huan
H
Xu
Bin
B
D001554:Benzene / Q000737:chemistry; D002384:Catalysis; D002851:Chromatography, High Pressure Liquid; D004867:Equipment Design; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006861:Hydrogen Peroxide / Q000737:chemistry*; D017665:Hydroxyl Radical; D008745:Methylation; D008872:Microwaves; D012394:Rosaniline Dyes / Q000494:pharmacology*; D012996:Solutions; D021241:Spectrometry, Mass, Electrospray Ionization; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013997:Time Factors; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods*
D012394:Rosaniline Dyes; D012996:Solutions; D014874:Water Pollutants, Chemical; C005095:malachite green; D017665:Hydroxyl Radical; D006861:Hydrogen Peroxide; D001554:Benzene