Kinetic Evaluation of Bismarck Brown Y Azo Dye Oxidation by Fenton Processes in the Presence of Aromatic Mediators
2021
Lima, Juan Pablo Pereira | Tabelini, Carlos Henrique Borges | Ramos, Márcio Daniel Nicodemos | Aguiar, André
Diverse aromatic mediators have often been used to increase the degradation of organic pollutants by Fenton reaction (Fe²⁺ + H₂O₂ → Fe³⁺ + HO● + HO⁻). The presence of reducing mediators can minimize the accumulation of Fe³⁺ in solution, which leads to accelerated Fe²⁺ regeneration and enhances the generation of reactive oxygen species, such as the HO● radical, i.e., the strongest oxidant in Fenton-based processes. On the other hand, a few non-reducing compounds can be converted into reducing intermediates during reactions, in addition to assisting degradation processes. Therefore, the influence of aromatic mediators, reducers and non-reducers, on decolorization kinetics of Bismarck Brown Y (BBY) dye oxidized by Fenton processes (Fe²⁺/H₂O₂, Fe³⁺/H₂O₂) has been investigated herein by using data from a previous study that had been developed by the present research group. In general, the second-order reaction kinetic model was better fit to the experimental data. Improvements in apparent second-order rate constants (k₂) were observed due to the presence of mediators. Reducers were more effective than non-reducers in increasing k₂ values. In another kinetic model, BMG, maximum oxidation capacity was increased due to the presence of mediators. In a new set of experiments, a decrease in apparent activation energy was verified due to introducing mediators into reactions initially containing either Fe²⁺ or Fe³⁺ as catalysts to oxidize BBY at different temperatures. This indicates that the tested mediators, two reducers (hydroquinone, gallic acid) and a non-reducer (salicylic acid), can decrease the energy barrier to allow Fenton reaction to oxidize dyes more effectively.
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