Characterization of a Bi2O3 coat based anode prepared by galvanostatic electrodeposition and its use for the electrochemical degradation of Reactive Orange 4

Two anodes were prepared by galvanostatic electrodeposition from an acidic Bi(III) solution on a Ti substrate and calcination in air at 350 degrees C and 600 degrees C. The surface coat of the anode calcined at 350 degrees C displayed irregular, predominantly sheet-like and needle-like morphology and it was composed of alpha-Bi2O3, with minor amounts of rhombohedral Bi and beta-Bi2O3, and traces of omega-Bi2O3. The surface coat of the anode calcined at 600 degrees C predominantly displayed an oval morphology, and it was composed solely of alpha-Bi2O3. Only this anode was electrochemically stable. TG analysis showed that it was chemically stable in the investigated temperature range from 25 degrees C to 600 degrees C, both in oxygen and nitrogen. This anode was used for electrochemical decolorization of a dye, Reactive Orange 4, in the presence of H2O2. The optimal values for the decolorization parameters (applied current density, H2O2 and Na2SO4 concentration and pH), which provided the fastest decolorization, were determined. Decolorization reactions follow pseudo-first order kinetics. (C) 2014 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.