Sequential photocatalysis and biological treatment for the enhanced degradation of the persistent azo dye methyl red

[Display omitted] •Methyl red (MR) was partially degraded by photocatalytic treatment with ZnO.•Following photocatalytic treatment with biotreatment maximized MR degradation.•MR elevated enzyme activities in a microbial consortium used for biotreatment.•The MR azo bond was cleaved by the sequential...

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Bibliographic Details
Published in:Journal of hazardous materials 2019-06, Vol.371, p.115-122
Main Authors: Waghmode, Tatoba R., Kurade, Mayur B., Sapkal, Ramchandra T., Bhosale, Chandrakant H., Jeon, Byong-Hun, Govindwar, Sanjay P.
Format: Article
Language:English
Subjects:
Decolorization
Degradation
Integrated treatment
Microbial consortium
Photocatalysis
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Summary:[Display omitted] •Methyl red (MR) was partially degraded by photocatalytic treatment with ZnO.•Following photocatalytic treatment with biotreatment maximized MR degradation.•MR elevated enzyme activities in a microbial consortium used for biotreatment.•The MR azo bond was cleaved by the sequential treatment.•The products of the sequential treatment were nontoxic to sorghum and black gram. A combination of photocatalysis and biodegradation is a promising approach for the removal of xenobiotic organic compounds from wastewater, since photocatalysis cleaves the molecules into simpler intermediates that are later mineralized by microorganisms. Sequential photocatalytic and biological treatment (SPABT) consisting of ZnO as a photocatalyst and a microbial consortium (Galactomyces geotrichum and Brevibaccilus laterosporus) enhanced the degradation of a model textile dye, methyl red (MR). SPABT completely decolorized 500 mg MR/L within 4 h. Biotreatment alone required 6 h for 100% decolorization. A maximum of 70% decolorization was achieved with the photocatalytic treatment but reductions in COD and toxicity were not adequate. Significant elevated activities of enzymes, including azo reductase, laccase and veratryl alcohol oxidase, were observed in the microbial consortium after exposure of MR. The degradation pathway and products of MR varied with treatment applied. The persistent azo bond was cleaved by following photocatalytic treatment with the microbial biotreatment. Tests with Sorghum vulgare and Phaseolus mungo indicated the products obtained by SPABT were non-phytotoxic.
ISSN:0304-3894
1873-3336
DOI:10.1016/j.jhazmat.2019.03.004