Synthesis and characterization of new Ti–Bi2O3 anode and its use for reactive dye degradation

This paper reports the synthesis, characterization and application of a Ti–Bi2O3 anode for the electrochemical decolorization of the textile dye Reactive Red 2. The anode was synthesized by electrodeposition on a Ti substrate immersed in an acidic bismuth (III) solution at constant potential, followed by calcination in air at 600 °C. Thermogravimetric Analysis (TGA), Energy-dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) analysis revealed that the electrodeposited material was predominantly metallic bismuth, which was oxidized to pure α-Bi2O3 during the calcination in air. SEM micrographs revealed that the Bi2O3 coat at the anode surface was inhomogeneous and porous. Reactive Red 2 was completely electrochemically decolorized at the synthesized anode in the presence of H2O2. The applied current density, H2O2 and Na2SO4 concentration, medium pH and initial dye concentration affected the dye decolorization rate. The optimal process parameters were found to be as follows: an applied current density of 40 mA cm−2 using a mixture of 10 mmol dm−3 H2O2 and 10 mmol dm−3 Na2SO4 at pH 7. The dye decolorization rate was shown to decrease as its initial concentration increased. The decolorization reactions were found to follow pseudo-first order kinetics.