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J Hazard Mater. 2019 Mar 5;365:448-456. doi: 10.1016/j.jhazmat.2018.11.036. Epub 2018 Nov 12.

Degradation of nitrobenzene by synchronistic oxidation and reduction in an internal circulation microelectrolysis reactor.

Author information

1
Department of Environmental Engineering, Beijing Institute of Petrochemical Technology, 19 Qingyuan North Road, Daxing District, Beijing 102617, PR China. Electronic address: hanyanhe@bipt.edu.cn.
2
Department of Environmental Engineering, Beijing Institute of Petrochemical Technology, 19 Qingyuan North Road, Daxing District, Beijing 102617, PR China.
3
Research Center for Eco-Environmental Engineering, Dongguan University of Technology, Dongguan, Guangdong 523808, PR China. Electronic address: niujf@dgut.edu.cn.
4
Griffith School of Environment, Gold Coast Campus, Griffith University, QLD 4222, Australia.

Abstract

The degradation of nitrobenzene by synchronistic oxidation and reduction was investigated using an internal circulation microelectrolysis (ICE) reactor with an active volume of 0.018 m3. Compared with a conventional fixed bed reactor with and without aeration, the ICE reactor exhibited a markedly higher nitrobenzene degradation efficiency. The effects of various operational parameters such as reaction time, aeration rate, initial nitrobenzene concentration, initial pH, and a volume ratio of iron and carbon (Fe/C) were also investigated. The optimal operating conditions (reaction time = 60 min, aeration rate = 5 × 10-4 m3/s, initial concentration of nitrobenzene = 300 mg/L, pH = 3.0, Fe/C = 1:1) gave removal efficiencies of nitrobenzene and chemical oxygen demand of 98.2% and 58%, respectively. The biodegradability index of the treated nitrobenzene solution was 0.45, which is 22 times that of the original solution. The reaction intermediates were identified through high-performance liquid chromatography, ultraviolet-visible spectroscopy, Fourier transform infrared spectroscopy, gas chromatography-mass spectrometry, and ion chromatography. The primary intermediates were determined to be aniline, phenol, and carboxylic acids, indicating that nitrobenzene was synchronously oxidized and reduced in the ICE reactor. Based on the identified intermediates, a possible pathway for nitrobenzene degradation in the ICE reactor is proposed.

KEYWORDS:

Degradation pathway; Internal circulation microelectrolysis reactor; Iron–carbon; Nitrobenzene; Synchronistic oxidation and reduction

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