Evaluation of color removal efficiencies and kinetic parameters of Fenton (H2O2/Fe2+) and photo-Fenton (H2O2/Fe2+/UV) processes in the treatment of a textile wastewater containing indigo blue / Avaliação da eficiência de remoção de cor e parâmetros cinéticos dos processos de Fenton (H2O2/Fe2+) e foto-Fenton (H2O2/Fe2+/UV) no tratamento de um efluente têxtil contendo corante azul índigo

The textile industry uses Indigo blue dye extensively in the production of jeans. Thus, high volumes of wastewater containing dye are obtained and must be treated before being discharged. The color removal efficiencies of indigo blue dye synthetic wastewater after treatment by Advanced Oxidative Processes (AOPs) using Fenton (H2O2/Fe2+) and photo-Fenton (H2O2/Fe2+/UV) was evaluated in this work. The experiments were conducted at pH 2.8 and evaluated the influence of the amount of [H2O2]/[Fe2+], the use of sulfuric acid and citric acid to adjust the pH, the initial concentration of the indigo dye, and the dosage form of H2O2 - the kinetic parameters and BMG model were also evaluated. The use of sulfuric acid to adjust the pH was more efficient in removing the color. The highest color removal rates were 70.78 ± 2.96 % after 180 min and 64.22 ± 2.08 % after 60 min, respectively, for the Fenton and photo-Fenton processes (both with a single dose of reagents) and 79.76 ± 1.45 % after 300 min and 80.43 ± 1.27% after 180 min, respectively, for Fenton and photo-Fenton with the gradual addition of H2O2. The indigo dye degradation reactions are better suited to the BMG kinetic model.