Improvement of the robustness of solar photo-Fenton processes using chemometric techniques for the decolorization of azo dye mixtures

• Chemometric techniques were applied to decolorize ternary azo dye mixtures.
• Partial least squares provided a rapid way to quantify dye mixtures.
• Central composite design suggested the appropriate reagent dose for decolorization.
• The strategy reduced the required amount of peroxide and the undesirable reactions.

The aim of this study was to propose and to evaluate a strategy based on chemometric tools to improve the robustness of photo-Fenton processes during decolorization of mixtures of sulfonated azo dyes. The strategy consisted of three stages: quantification, reagent dose selection and robustness analysis. The partial least square method was used for the simultaneous quantification of acid orange 7, acid red 151, and acid blue 113, in a mixture, by using UV-visible spectra. Then, a central composite design was applied to set the best reagent dose (Fe2+ and H2O2) to obtain a decolorization of 97% for each dye. The application of the strategy allowed to predict the concentration of each dye and to select the best reagent dose to decolorize mixtures of sulfonated dyes. Also with the application of the developed strategy, a reduction of peroxide from 33 to 65% was obtained and the undesirable reactions were reduced. It was observed that the variation of dye concentrations do not affected the percentage of decolorization.