Preparation and characterization of Sb₂O₅-doped Ti/RuO₂-ZrO₂for dye decolorization by means of active chlorine

Textile industry is one of the major generators of wastewaters containing recalcitrant compounds such as dyes that jeopardize public health and environment. Electro-oxidation is an alternative method for treating recalcitrant compounds, and the key element for efficient degradation is the adequate use of dimensionally stable anode (DSA) electrodes to efficiently generate active chlorine, which degrades dyes contained in effluents into more environment-friendly compounds. This work is thereby aimed at preparing a novel DSA electrode for efficient generation of active chlorine. Two different dimensionally stable anodes (Ti/RuO₂and Sb₂O₅-doped Ti/RuO₂-ZrO₂) were prepared and then characterized by grazing incidence X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy, which corroborated the presence of RuO₂, ZrO₂, and Sb₂O₅. The comparison of electroactive areas, assessed by chronoamperometry, showed that Zr helps increase the area of the ternary electrode facilitating the formation of active chlorine. Active chlorine formation was further studied by cyclic voltammetry that revealed a reduction peak attributed to chlorine (product of chloride oxidation). Additionally, decolorization of model solutions that simulate textile effluents containing indigo carmine and reactive black 5 in media with and without chlorides was performed. In the chloride-containing medium, decolorization occurred at a faster rate than in the presence of sulfates. Decolorization of carmine indigo and reactive black 5 in the chloride-containing medium took 40 min and 2 h, respectively. In conclusion, the DSA electrode made of Sb₂O₅-doped Ti/RuO₂-ZrO₂can efficiently generate the active chlorine for degradation of recalcitrant compounds.