Degradation of Indigo Carmine and Reactive Black 5 Dyes with Sb2O5-Doped Ti/RuO2-ZrO2 DSA in a Parallel-Plate Flow Reactor Via Active Chlorine

Wastewater from the textile industry is highly colored and of a complex and variable nature. The substantial amount of dyestuffs used in the dyeing stage of textile manufacturing processes represents an increasing environmental danger due to their refractory nature [1]. The treatment of textile wastewater by conventional methods such as biological and chemical processes or their combination are in common practice but have several drawbacks, e. g. inefficient color removal and/or the formation of toxic by-products [2]. On the other hand, electrochemical oxidation is a very promissory process for refractory pollutants degradation since no chemical reagents are needed and no secondary wastes are formed.

In the present study, electrochemical degradation experiments were conducted to degrade a textile dyes namely indigo carmine (IC) and reactive black 5 (RB). A FM01-LC reactor was used to investigate the effect of various operating parameters using a dimensionally stable anode (DSA, Sb₂O₅-doped Ti/RuO₂-ZrO₂). The oxidation of IC and RB takes place in the bulk solution with electrolytically generated active chlorine (chlorine, hypochlorite ion and hypochlorous acid). Figure 1 shows the normalized color decay. For the indigo carmine decolorization occurs in 80 min, whereas for the reactive black it takes 2 h.  The difference in the time of decolorization is due to the structure of each dye the structure of reactive black 5 is larger than that of indigo carmine.

[1] Balcioglu I.A., Arslan I. and Sacan T. Homogenous and heterogenous advances oxidation of two commercial reactive dyes, Environment technology, 22 (2001), pp. 813-822.

[2] Rajkumar D., Joo Song B. and Guk Kim J., Electrochemical degradation of Reactive Blue 19 in chloride medium for the treatment of textile dyeing wastewater with identification of intermediate compounds, Dyes and Pigments, 72 (2007), pp. 1-7.