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Water Res. 2019 Jun 1;156:1-8. doi: 10.1016/j.watres.2019.02.057. Epub 2019 Mar 11.

Activation of ferrate by carbon nanotube for enhanced degradation of bromophenols: Kinetics, products, and involvement of Fe(V)/Fe(IV).

Author information

1
School of Civil Engineering and Architecture, University of Jinan, Jinan, 250022, China.
2
Institute of Environmental and Ecological Engineering, Guangdong University of Technology, Guangzhou, Guangdong, 510006, China.
3
School of Civil Engineering and Architecture, University of Jinan, Jinan, 250022, China. Electronic address: lipingqiu@163.com.
4
Key Laboratory of Songliao Aquatic Environment, Ministry of Education, School of Municipal and Environmental Engineering, Jilin Jianzhu University, Changchun, 130118, China. Electronic address: psyhit@126.com.
5
State Key Laboratory of Urban Water Resource and Environment, School of Municipal and Environmental Engineering, Harbin Institute of Technology, Harbin, 150090, China.
6
Key Laboratory of Eco-environments in Three Gorges Reservoir Region, Ministry of Education, School of Urban Construction and Environmental Engineering, Chongqing University, Chongqing, 400045, China.
7
School of Light Industry&Chemistry Engineering, Dalian Polytechnic University, Dalian, 116034, China.

Abstract

Very recently, several studies have found that homogeneous reducing agents (e.g., sodium thiosulfate (Na2S2O3), and sodium sulfite (Na2SO3)) can activate ferrate to enhance the degradation of selected contaminants. In this work, it was found that heterogeneous carbon nanotube (CNT) could accelerate ferrate (Fe(VI)) for the degradation of bromophenols (BrPs) of environmental concerns and alleviate the appearance of undesired by-products in effluent. Fe(VI) could react with BrPs over a wide pH range of 6-10 with apparent second-order rate constants of 1.8-1850 M-1 s-1. Electrospray ionization-triple quadrupole mass spectrometry (ESI-QqQMS) analysis showed that dibrominated dihydroxylated biphenyls and dibrominated phenoxyphenols were possibly formed via coupling reaction of BrPs radicals generated from Fe(VI) oxidation through one-electron transfer. The presence of CNT could remarkably accelerate the degradation rates of BrPs by Fe(VI) in a wide pH range from 7 to 10. Moreover, the formed undesired polybrominated products during Fe(VI)/CNT oxidation were absorbed on CNT surface and thus removed from treated water. The Fe(VI)/CNT system was capable of selectively oxidizing electron-rich pollutants (e.g., BrPs, and sulfamethoxazole (SMX)), but reluctant to iopamidol (IPM) and nitrobenzene (NB). High-valent metal-oxo intermediates Fe(V)/Fe(IV) formed in situ from the reaction of CNT with Fe(VI) were likely responsible for this activation effect of CNT, which was further confirmed via using methyl phenyl sulfoxide (PMSO) as a probe compound. Comparatively, homogeneous reducing agent Na2S2O3 could enhance Fe(VI) degradation of BrPs at pH 7 and 8, while undesired polybrominated products were detected in effluent from Fe(VI)/Na2S2O3 system. These findings have crucial implications for the development of a promising oxidation process by combination of Fe(VI) and CNT for water and wastewater treatment.

KEYWORDS:

Bromophenols; Carbon nanotube; Ferrate; High-valent metal-oxo intermediates; Polybrominated products

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