Oxidative degradation of azo dye by hydrogen peroxide electrogenerated in situ on anthraquinonemonosulphonate/polypyrrole composite cathode with heterogeneous CuO/γ-Al2O3 catalyst

Heterogeneous electrocatalytic wet H2O2 oxidation technique for the removal of azo dye amaranth from aqueous solution was studied in the presence of solid CuO/gamma-Al2O3 catalyst and anthraquinonemonosulphonate/polypyrrole (AQS/PPy) composite cathode able to electrogenerate H2O2 in situ. The spherical CuO/gamma-Al2O3 catalysts with various CuO loadings and calcined at different temperatures were characterized by BET, ESEM-EDS, XRD and XPS. Several parameters affecting H2O2 electrogeneration and dye degradation such as solution pH, cathode potential (E-ca), oxygen flow rate (V-O2), CuO loading, reaction temperature as well as catalyst calcination temperature were investigated. Experimental results revealed that the optimal condition for H2O2 electrogeneration on the AQS/PPy composite modified cathode is V-O2 = 0.4 ml min(-1), E-ca = 0.4V and pH 4.3. On this occasion, ca. 90% chroma decay and 60% TOC removal of dye were achieved with 450 degrees C-calcined 5.78 wt%-CuO/gamma-Al2O3 catalyst and 70 degrees C reaction temperature. Dye degradation follows the second-order kinetics. Leaching tests showed that the leaching copper amount during the oxidation is only 4.0-7.0% per run and the role of heterogeneous activity is dominant. The catalytic activity of CuO/gamma-Al2O3 catalyst could be recovered after multiple runs by a re-calcination step. Furthermore, the stability of the AQS/PPy composite after consecutive operation was also investigated by chronoamperometric and EIS techniques. (C) 2011 Elsevier B.V. All rights reserved.