Electrochemical incineration of indigo textile dye in filter-press-type FM01-LC electrochemical cell using BDD electrodes

This work shows results obtained in the incineration of 1 mM indigo textile dye (536 ppm COD) in 0.05 M NaCl aqueous media (which resembles a denim laundry industrial wastewater). Microelectrolysis and macroelectrolysis studies indicated that oxidation of indigo dye was carried out via hydroxyl radicals (OH) formed by water oxidation on the BDD surface, instead of active chlorine as usually occurs by using DSA. Electrolyses in a FM01-LC reactor was performed at Reynolds between 1600 < Re < 18300, and a fixed current density of 5.3 and 15 mA cm−2. The experimental set-up achieved 100% efficiency in color removal, indigo mineralization and current efficiency. Estimated energy consumption, at Re = 12892 and J = 5.3 mA cm−2, was 9 kWh m−3. Experimental data revealed that hydrodynamic conditions do not influence either the indigo degradation rate or the current efficiencies; therefore indigo degradation must involve a complex mechanism.