Journal
JOURNAL OF ELECTROANALYTICAL CHEMISTRY
Volume 847, Issue -, Pages -Publisher
ELSEVIER SCIENCE SA
DOI: 10.1016/j.jelechem.2019.04.048
Keywords
Indigo Carmine; Photoelectrocatalysis; Photoelectro-Fenton; Anodized Ti; Water treatment
Categories
Funding
- Universitet de Barcelona under Grant AUCANI [787]
- AEI/FEDER, EU [CTQ2016-78616-R]
- MINECO (Spain)
- Brazilian National Council for Scientific and Technological Development - CNPq [465571/2014-0]
- Brazilian Sao Paulo Research Foundation (FAPESP) [50945-4]
- Brazilian Coordenacao de Aperfeicoamento de Pessoal de Nivel Superior Brasil (CAPES) [001]
- University of Sao Paulo under Grant AUCANI [787]
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This article reports the synthesis of TiO2 nanotube arrays (TiO2 NTs), grown by Ti anodization, and their use as photoanode in a hybrid photelectrocatalytic (PEC)/photoelectro-Fenton (PEF) treatment of Indigo Carmine solutions in sulfate medium at pH 3.0. The anode was combined with an air-diffusion cathode that ensured continuous H2O2 electrogeneration. Comparative trials by electrochemical oxidation with electrogenerated H2O2 (EO-H2O2), electro-Fenton (EF) and PEF with Pt anode were made. The photoanode was stable operating up to 3 mA cm(-2) with irradiation from a 36-W UV LED lamp, showing photoelectroactivity from an anodic potential (E-4n) of +0.20 V, as determined by cyclic voltammetry. At 3 mA cm(-2), color removal by EO-H2O2 with Pt and PEC with TiO2 NTs was very slow, being much faster in EF, PEF and PEC/PEF due to main role of (OH)-O-center dot formed from Fenton's reaction upon addition of Fe+. The absorbance and dye concentration decays agreed with a pseudo-first-order kinetics, yielding a slightly lower rate constant for decolorization because of the formation of colored products. The mineralization ability increased as: EO-H2O2 << EF PEF < PEC/PEF. The holes photogenerated at the TiO2 NTs surface had higher oxidation ability than (OH)-O-center dot formed at the Pt surface from water discharge. In PEC/PEF, a slower mineralization was found at 2 mA cm(-2), although the final mineralization percentage was similar to that attained at 3 mA cm(-2). Both, SO42- and NH4+ ions were released during the treatments, along with isatin-5-sulfonic and formic acids as main products.
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