Use of statistical experimental design to optimize the degradation of textile effluents by the Fenton homogeneous process with organic complexes

One of the main limitations of the conventional Fenton process applied to the treatment of textile effluents is the need to acidify the effluent at a pH close to 3. In order to allow the treatment of a textile effluent at a pH near neutral, the application of the Fenton homogeneous process with six organic complexants alone was evaluated in this research, these being: ascorbic acid (AA), citric acid (CA), ethylenediaminetetraacetic acid (EDTA), gluconic acid (GA), oxalic acid (OA) and tartaric acid (TA). The optimization of the reactor operating conditions pH, catalyst concentration (Fe2+), oxidant (H2O2) and the complexing agent were obtained by the experimental design of the Rotational Central Compound Design (RCCD). (1:1.31:1.2:27.94) of the different total organic carbon (TOC) molar ratios of the textile effluent, Fe2+, complexant and H2O2 (TOC:Fe2+:AG:H2O2), followed by the TA when subjected to the molar ratio [1:0.74:0.94:32.13], both with no change in the pH value of the textile effluent (6.71) were used to obtain 82.30% TOC, 99.27% turbidity and 99.19% apparent color, with the use of GA for 15 h of reaction and 75.05% of TOC, 97.84% of turbidity and 96.75% apparent color in 12 h of reaction with TA application. Thus, the Fenton homogeneous process with organic complexes TA and GA allowed the average removal of 75% and 82%, respectively, under a wide operational pH range (4–11) for TOC. Finally, the use of an organic complexant allowed the treatment of textile effluent in a wide range of pH values, hence optimizing the Fenton process application in the treatment of these effluents.