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Removal of Reactive Dyes from Aqueous Solution by Fenton Reaction: Kinetic Study and Phytotoxicity Tests

Tavares, Marcela G. R., Santos, Danilo H. S., Tavares, Mariana G., Duarte, José L. S., Meili, Lucas, Pimentel, Wagner R. O., Tonholo, Josealdo, Zanta, Carmem L. P. S.
Water, air, and soil pollution 2020 v.231 no.2 pp. 82
absorbance, analysis of variance, aqueous solutions, discoloration, hydrogen peroxide, iron, phytotoxicity, reactive dyes, response surface methodology, statistical models, textile mill effluents
Fenton process was successfully applied to degrade three reactive dyes, blue 19 (RB19), red 195 (RR195), and yellow 145 (RY145), a mixture of dyes and a real textile effluent. A 2³ full factorial design coupled with a response surface methodology (RSM) was conducted to evaluate the effects of H₂O₂, Fe²⁺, and dye concentration on the Fenton reaction measured by absorbance reduction (AR) as response. Considering the analysis of variance (ANOVA), the statistical models could be used to describe experimental results and to predict the process behavior. The results obtained by RSM indicated that the optimum conditions for Fenton were [H₂O₂] = 50 mg L⁻¹, [Fe²⁺] = 0.5 mmol L⁻¹, and dye concentration = 0.075 g L⁻¹, obtaining up to 90% of AR. From kinetic study, the absorbance reduction for RY145 followed a second-order model, while RB19 and RR195 followed a first-order model. The mixture of dyes and the real textile effluent obtained lower AR, 56% and 22%, respectively. The phytotoxicity tests indicate that the Fenton reactions were very effective to reduce the toxicity of almost all contaminated solutions; however, for more complex solution (mixture of dyes and real effluents), a longer reactional time is necessary. Therefore, the results pointed that the Fenton reaction is very efficient in solution discoloration.