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Comparison of degradation mechanism of electrochemical oxidation of di- and tri-nitrophenols on Bi-doped lead dioxide electrode: Effect of the molecular structure

Paper ID Volume ID Publish Year Pages File Format Full-Text
47739 46481 2009 16 PDF Available
Title
Comparison of degradation mechanism of electrochemical oxidation of di- and tri-nitrophenols on Bi-doped lead dioxide electrode: Effect of the molecular structure
Abstract

In the present work, the effect of molecular structures of di- and tri- nitrophenols on electrochemical degradation has been investigated on Bi-doped lead dioxide electrodes in terms of cyclic voltammetry and bulk electrolysis. The results of SEM and AFM displayed a porous structure with small-sized crystal particles and compact crystalline structure of Ti/Bi-PbO2. These nitrophenols were believed to be mainly degraded by means of indirect oxidation due to the low anodic oxidation currents observed in cyclic voltammetries and large amount of oxidants. And the absence of polymeric adhesive compounds formed and deposited on the surface of electrodes indicated the high electrocatalytic activity of Ti/Bi-PbO2 for decomposing organics. Within the present experimental conditions used, almost complete elimination of nitrophenols was achieved. The electrochemical oxidation of them followed in the order: 2,6-dinitrophenol > 2,5-dinitrophenol > 2,4-dinitrophenol > 2,4,6-trinitrophenol. The relationship between electrochemical oxidation rate and the molecular structure of nitrophenols was discussed. The results of LC/MS and HPLC suggested that three kinds of intermediates were generated, i.e., polyhydroxylated intermediates, reduction products of nitrophenols and carboxylic acids. The possible degradation pathways of nitrophenols were proposed. The denitration and substitution by hydroxyl radicals on aromatic rings seemed to be the first stage. As a consequence, the formation of polyhydroxylated intermediates took place. These compounds were successively oxidized into catechol, resorcinol and hydroquinone, as well as reduced to aminophenols, followed by the opening of aromatic rings and the formation of a series of carboxylic acids. Finally, these carboxylic acids were oxidized into CO2 and H2O.

Keywords
Nitrophenol; Electrochemical oxidation; Mechanism; Bi-doped lead dioxide electrode; Molecular structure
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Comparison of degradation mechanism of electrochemical oxidation of di- and tri-nitrophenols on Bi-doped lead dioxide electrode: Effect of the molecular structure
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis B: Environmental - Volume 91, Issues 1–2, 7 September 2009, Pages 284–299
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
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Any Questions? feel free to contact us