title: An integrated (electro- and bio-oxidation) approach for remediation of industrial wastewater containing azo-dyes: Understanding the degradation mechanism and toxicity assessment.
abstract: A hybrid approach for the remediation of recalcitrant dye wastewater is proposed. The chlorine-mediated electrochemical oxidation of real textile effluents and synthetic samples (using Ti/IrO2-RuO2-TiO2 anodes), lead to discoloration by 92% and 89%, respectively, in 100min, without significant mineralization. The remediation was obtained through biodegradation, after removing the residual bio-toxic active chlorine species via sunlight exposition. Results show that the electrochemical discoloration enhances the effluent biodegradability with about 90% COD removal employing acclimatized naphthalene-degrading bacterial consortia, within 144h. Based on results obtained through FT-IR and GC-MS, it is likely that azo group stripping and oxidative cleavage of dyes occur due to the nucleophilic attack of active chlorine species during electro-oxidation. This leads to generation of aromatic intermediates which are further desulfonated, deaminated or oxidized only at their functional groups. These aromatic intermediates were mineralized into simpler organic acids and aldehydes by bacterial consortia. Phyto-toxicity trials on Vigna radiata confirmed the toxic nature of the untreated dye solutions. An increase in root and shoot development was observed with the electrochemically treated solutions, the same was higher in case of bio-treated solutions. Overall, obtained results confirm the capability of the proposed hybrid oxidation scheme for the remediation of textile wastewater.
authors.affiliation: Corrosion and Materials Protection Division (CMPD), CSIR-Central electrochemical research institute (CECRI), Karaikudi 630 003, India. Electronic address: priya.bdu07@gmail.com.
authors.forename: Priyadharshini
authors.initials: P
authors.lastname: Aravind
authors.affiliation: Corrosion and Materials Protection Division (CMPD), CSIR-Central electrochemical research institute (CECRI), Karaikudi 630 003, India.
authors.forename: Hosimin
authors.initials: H
authors.lastname: Selvaraj
authors.affiliation: Ecas4 Australia, Unit 8, 1 London Road, Mile End, South Australia 5031, Australia.
authors.forename: Sergio
authors.initials: S
authors.lastname: Ferro
authors.affiliation: Corrosion and Materials Protection Division (CMPD), CSIR-Central electrochemical research institute (CECRI), Karaikudi 630 003, India.
authors.forename: Maruthamuthu
authors.initials: M
authors.lastname: Sundaram
mesh_terms: D001391:Azo Compounds / Q000737:chemistry* / Q000633:toxicity*; D001419:Bacteria / Q000378:metabolism; D001673:Biodegradation, Environmental; D057919:Biological Oxygen Demand Analysis; D004396:Coloring Agents / Q000737:chemistry* / Q000633:toxicity*; D055664:Electrochemical Techniques; D052918:Environmental Restoration and Remediation / Q000379:methods*; D008401:Gas Chromatography-Mass Spectrometry; D007220:Industrial Waste; D010084:Oxidation-Reduction; D010944:Plants / Q000187:drug effects; D017550:Spectroscopy, Fourier Transform Infrared; D013472:Sunlight; D013783:Textile Industry; D000070658:Vigna / Q000187:drug effects / Q000254:growth & development; D062065:Wastewater / Q000737:chemistry* / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000737:chemistry* / Q000633:toxicity*
chemical_list: D001391:Azo Compounds; D004396:Coloring Agents; D007220:Industrial Waste; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Biodegradation; Hybrid treatment; Phyto-toxicity; Textile effluent; Ti/IrO(2)-RuO(2)-TiO(2)