Degradation of Blue 1 and Yellow 6 Dyes in Binary Mixture Using Photo-Fenton/Sunlight System: Optimization by Factorial Designs

Effluents from the food industry regularly contain synthetic dyes that cause damage to ecosystems and water bodies. The present work aimed to evaluate homogeneous advanced oxidation processes for the mixed degradation of food dyes blue 1 and yellow 6. Through preliminary studies of advanced oxidation processes by photolysis, UV/H2O2, Fenton, and photo-Fenton, applying UV-C, artificial solar (sunlight), and natural solar radiation, the system with the best performance for the integral optimization of the treatment was determined. Based on the treatment with the best results, the multilevel factorial design 2(2)x3(1) and central composite design 2(boolean AND)2 + star were created to optimize the variables [H2O2], [Fe], and pH. The kinetics of the process was evaluated based on the percentages of degradation of the chromophore groups and reduction of the chemical oxygen demand. The post-treatment samples were tested for toxicity on lettuce Lactuca sativa germination to verify the effect of the advanced oxidation process employed. The most efficient treatment determined in the preliminary study was photo-Fenton assisted by sunlight radiation. Under the best conditions developed and analyzed with the experimental designs, a 99% degradation of the chromophore groups was achieved, and a 98.72% decrease in chemical oxygen demand, in 120 min. The experimental data were well represented by the nonlinear kinetic model proposed by Chan and Chu with values of R-2 > 0.95. The toxicity test results demonstrated a decrease in the root growth of the species Lactuca sativa. The results demonstrate that the photo-Fenton system assisted by sunlight radiation is an efficient method to remove food dyes in aqueous matrices.

Automated summary

This research evaluated homogeneous advanced oxidation processes for the mixed degradation of food dyes blue 1 and yellow 6, and optimized the treatment conditions through experimental designs. The most efficient treatment was determined to be photo-Fenton assisted by sunlight radiation, achieving high degradation rates and reduction in chemical oxygen demand within 120 minutes.