Journal of Hazardous Materials 205–206 (2012) 1–9 Contents lists available at SciVerse ScienceDirect Journal of Hazardous Materials jou rn al h om epage: www.elsevier.com/loc ate/jhazmat Assessment of by-products of chlorination and photoelectrocatalytic chlorination of an azo dye Rafael Leite de Oliveira a , Marc A. Anderson c , Gisela de Aragão Umbuzeiro b , Guilherme Julião Zocolo a , Maria Valnice Boldrin Zanoni a,∗ a Electroanalytical Chemistry Laboratory, Department of Analytical Chemistry, UNESP, University of São Paulo State, Brazil b Environmental Ecotoxicology and Microbiology Laboratory – LEAL, Faculty of Technology, University of Campinas, Limeira, SP, Brazil c Water Science and Engineering Laboratory 660 North Park Street, Madison, USA a r t i c l e i n f o Article history: Received 5 August 2011 Received in revised form 23 September 2011 Accepted 21 October 2011 Available online 29 November 2011 Keywords: CI Disperse Blue 291 Chlorination of dyes Removal of azo dye Phoelectrochemical chlorination Byproducts of chlorination a b s t r a c t The present work describes a more efficient methodology for the chlorination of water contain- ing disperse dyes, where the chlorinated byproducts identified by mass spectra are compared. For this investigation, we tested the degradation of CI Disperse Blue 291 dye, 2-[(2-Bromo-4,6- dinitrophenyl)azo]-5-(diethylamino)-4-methoxyacetanilide) a commercial azo dye with mutagenic properties. The present work evaluates the photoelectrocatalytic efficiency of removing the CI Disperse Blue 291 dye from a wastewater of the textile industry. We employed NaCl as a supporting electrolyte. It should be noted that photoelectrocatalytic techniques are non-conventional method of generating chlorine radicals. The by-products formed in this process were analyzed using spectrophotometry, liquid chromatography, dissolved organic carbon, mass spectral analysis and mutagenicity assays. The process efficiency was compared with the conventional chlorination process adopted during sewage and efflu- ents treatment processes. This conventional chlorination process is less efficient in removing color, total organic carbon than the photoelectrochemistry technique. Furthermore, we shall demonstrate that the mutagenicity of the generated by-products obtained using photoelectrocatalysis is completely differ- ent from that obtained by the conventional oxidation of chloride ions in the drinking water treatment process. © 2012 Published by Elsevier B.V. 1. Introduction The occurrence of mutagenic response to contaminants eminat- ing in some textile and wastewater treatment plants processing residuals from textile finishing companies has been reported in the literature [1–5]. The routine backtracking of wastewaters enter- ing treatment plants from the production plants of some textile processing companies has led to the identification of textile dyes as being a cause of the high mutagenic effects impacting the water exiting the treatment plant as well as drinking water quality [6–10]. CI Disperse Blue 291 dye, 2-[(2-Bromo-4,6-dinitrophenyl)azo]- 5-(diethylamino)-4-methoxyacetanilide) (Fig. 1) is a commercial azo dye (CAS 51868-46-3) highly used in the textile industry for dyeing polyester. The compound has hydrophobic proper- ties, which can easily adsorbed on aquatic sediments or forms stable suspensions that can be transported by receiving waters and ultimately reach water treatment plants [10]. The presence of CI Disperse Blue 291 and five 2-phenylbenzotriazole (PBTA) ∗ Corresponding author. Tel.: +55 1633019619. E-mail address: boldrinv@iq.unesp.br (M.V.B. Zanoni). derivatives has being detected in extracts obtained from several rivers in Japan that have been receiving effluents from textile dye- ing factories. Those dye related compounds have been the main source of the mutagenic activity detected in river waters [11]. CI Disperse Blue 291 was detected as a mutagenic for TA1537, TA1538, TA98, TA100, TA98DNP6, YG1024 and YG1041 strains of Samonella both with and without metabolic activation system (S9) [12,13]. The genotoxicity aspects of aminoazobenzenes dyes have been previously studied [14–17]. The chemical structure analy- sis involving these dyes showed that the mutagenic responses in Salmonella and mammalian assay systems depend on the nature and position of halogen substituents with respect to both the aro- matic rings and the amino nitrogen atom. Because minor changes in the molecule can drastically modify mutagenic activity and car- cinogenic potential, it is important that each azo dye released into the market is adequately tested. Among the aminoazobenzene dyes with nitro and halogenated substituents the only dye that has been extensively evaluated for mutagenicity has been the dinitrobro- moaminoazobenzene dye CI Disperse Blue 79 [18]. Because of the mutagenic properties of dye compounds, the development of meth- ods to treat and recycle wastewaters containing these compounds is an issue of immediate concerns due to the proven toxicity but yet 0304-3894/$ – see front matter © 2012 Published by Elsevier B.V. doi:10.1016/j.jhazmat.2011.10.060