Electrochemical reduction and oxidation pathways for Reactive Black 5 dye using nickel electrodes in divided and undivided cells |
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Authors: | Ana J Méndez-Martínez Martin M Dávila-Jiménez Omar Ornelas-Dávila María P Elizalde-González Uriel Arroyo-Abad Ignasi Sirés Enric Brillas |
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Affiliation: | 1. Facultad de Ciencias Químicas, Universidad Autónoma de Puebla, CU, Edif. 105H, 72570 Puebla, Pue, Mexico;2. Centro de Química. Instituto de Ciencias, Universidad Autónoma de Puebla, CU, Edif. 103H, 72570 Puebla, Pue, Mexico;3. Laboratori d’Electroquímica dels Materials i del Medi Ambient, Departament de Química Física, Facultat de Química, Universitat de Barcelona, Martí i Franquès 1-11, 08028 Barcelona, Spain |
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Abstract: | The cathodic reduction and anodic OH-mediated oxidation of the azo dye Reactive Black 5 (RB5) have been studied potentiostatically by using undivided and divided cells with a Ni-polyvinylchloride (Ni-PVC) composite cathode and a Ni wire mesh anode. Solutions of 50–100 cm3 of 20–80 mg dm?3 RB5 in 0.1 mol dm?3 KOH were degraded to assess the effect of electrolysis time and electrode potentials on the infrared and absorbance spectra, as well as on the decay of the total organic carbon and chemical oxygen demand. Reversed-phase high performance liquid chromatography (RP-HPLC) with ion-pairing and diode array detection (ion pair chromatography), along with coupling to tandem mass spectrometry (LC–MS/MS), were used for the identification of the aromatic degradation by-products and monitoring their time course. These analyses revealed the progressive conversion of the RB5 dye to simpler molecules with m/z 200, 369.5 and 547 under the direct action of the electron at the cathode and the formation of polar compounds such as alkylsulfonyl phenol derivatives with m/z 201, 185 and 171 by the OH mediation at the anode. From these results, the electrochemical reduction and oxidation pathways for the RB5 dye were elucidated. |
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