The role of dye's structure on the degradation rate during indirect anodic oxidation

Abstract

The aim of this work was to evaluate the possibility of decolorization of effluents that contain structurally different azo and aminoantrachinone dyes. The decolorization was performed by an indirect electrochemical oxidation in a single-chamber laboratory electrolyzer under galvanostatic mode. Anodes used for the treatment were a planar boron-doped diamond and a platinum electrode. The changes in decolorization rate of model solutions were measured during indirect electrochemical oxidation in dependence on different initial pH in the presence of sodium sulfate, which is frequently used during the dyeing process. The decolorization process was compared with another abundant salt, specifically sodium chloride. The time intervals corresponding to chromaticity change of electrolyzed solution were measured and kinetic constants were assessed. Results showed that the decolorization rate is higher in the presence of NaCl than Na2SO4 and the structure of the dye has a direct impact on the velocity of the decolorization process. However, the degradation evaluated by the determination of total organic carbon parameter showed promising results also in the presence of sulfates on the boron-doped diamond anode dropping from 104 to 21 mg dm(-3). Since this parameter decreased on Pt anode only to 98 mg dm(-3), boron-doped diamond anode showed better performance in the presence of sulfates.