Degradação eletroquímica do corante Reactive Red 239 usando Ti/TiO2RuO2IrO2

The textile sector generates a high volume of effluent that sometimes is discarded without treatment, causing impacts on the environment and public health. Due the social importance of this activity and the environmental impact generated, this study aimed to evaluate the performance of the Ti/TiO2RuO2IrO2 anode in the degradation of Reactive Red 239 dye in solution (RR239, 25 mg L-1). The galvanostatic electrolysis was performed at different current densities (10, 20 and 40 mA cm-2) at 25 °C, and using as supporting electrolyte Na2SO4 and H2SO4 (0.1 mol L-1). In the electrochemical process was employing an undivided cell (0.5 L of solution) with parallel plates of 64 cm2 of geometric area. The efficiency of degradation process was evaluated by reduction of total organic carbon (TOC) and absorption of solution in the UV-Visible region, as a function of electrolysis time. Absorption spectrum of the RR239 dye showed two bands, one in 543.9 nm, which is attributed to the transition n → π*, referring to the azo group (-N = N-) and responsible for the coloring [1], and the other band in 289.1 nm, referring to π → π* transition, which is assigned to aromatic ring systems; both absorption bands were completely eliminated. In the initial study, the highest discoloration rate and TOC removal occurred in the density of 40 mA cm-2 using H2SO4 as electrolyte. In this conditions was studied the effect of temperature (25, 40 and 60 ºC) and the oxidizing effect of chlorine active species electrogenerated adding chloride in three concentrations (10-1 , 10-2 and 10-3 mol L-1). The temperature increase reduced the time of the colour removal from 180 at 25 °C to 120 minutes at 40 °C, and to 60 minutes at 60 °C. The complete removal of TOC was at 180, 180 and 120 minutes at 25 °C, 40 °C and 60 °C, respectively. The addition of chloride in the solution reduced significantly the discoloration race, occurring in up to 15 minutes in 10-3 mol L-1 chloride. However, high concentrations of chloride (0.1 mol L-1) did not favor the removal of TOC. Regarding the temperature increase in studies containing chloride, the electrode showed best performance in both discoloration kinetics and the TOC removal of solution. Considering the results, it was evidenced that the best treatment conditions were: H2SO4 0,1 mol L-1 , chloride 0,01 mol L-1 at 60 °C, requiring 15 minutes to discoloration of solution, and 120 minutes to total removal of TOC, applying at 20 mA cm-2 and consumed 17,21 kWh m3 of solution treated. The study showed that Ti/TiO2RuO2IrO2 electrode is effective in degradation of the RR239 dye, and represent a viable alternative to the electrochemical treatment of real textile effluents.