Degradation of recalcitrant organic compounds by electrochemical method

Degradation of recalcitrant organic compounds such as azo dye is difficult to accomplish because of their complex structure. This paper deals with the electrochemical oxidation of C.I. Reactive Black 5 (RB5) azo dye at dimensionally stable anodes (DSA). The Ti/RuO2/SnO2-SbO5-Bi2O3 electrodes were prepared by thermal decomposition of the appropriate precursors and they were characterized by scanning electron microscopy (SEM) and cyclic voltametry (CV). The SEM image revealed a surface morphology with mud-like cracks and the cyclic voltammograms suggested that the dye oxidation might occur simultaneously with oxygen evolution. The electrochemical oxidation of the dye was carried out in a cell with two anodes of Ti/RuO2/SnO2-Sb2O5-Bi2O3 and three cathodes of stainless steel. The elctrolyte solution consisted of 0.1 g/L dye in 0.1 M Na2SO4 as supporting electrolyte at pH 5.8, 11 and 3. The degradation of the dye was assessed by recording UV-VIS spectra of the electrolysed solutions. Colour removal efficiency higher than 96% was obtained for an apllied current density of 100 A/m2 and electrolysis time of 120 minutes at any value of the pH.