Kinetic behavior of C.I. Reactive Blue 182 towards oxidation with H 2 O 2 /UV and H 2 O 2 /NaOH systems

Abstract The need for cheap and efficient low-cost methodologies for water treatment is of great interest, since global fresh water demand is constantly increasing. In this context, this article reports comprehensive results on the oxidation kinetics of C.I. Reactive Blue 182 dye in aqueous solutions, using H 2 O 2 /NaOH and H 2 O 2 /UV as oxidant systems. Several variables were studied, including the influence of the H 2 O 2 (0.03–30%), NaOH (1.0–2.0 mol L −1 ) and dye (0.0173–0.0636 mmol L −1 ) concentrations, the temperature (30–70 °C) and the pH (6–12). Under the best conditions (0.0289 mmol L −1 of initial dye at pH 12), decolorization efficiencies of 99.8 and 98.9% were obtained for H 2 O 2 /NaOH (125 min, at 60 °C) and H 2 O 2 /UV (225 min, at 70 °C), respectively. When combining H 2 O 2 , NaOH and UV in the same reaction, under the conditions described above, the decolorization efficiency was 99.7% in 40 min. The kinetic data showed a pseudo-first order behavior and the positive values obtained for the thermodynamic parameters (E a and average ΔH # , ΔG # and ΔS # ) indicate that the processes required a low amount of energy and are endothermic in nature. The difference between the amounts of energy involved in the oxidation of the dye catalyzed by base or UV-light was small, which may indicate that the mechanisms involved in the decolorization and degradation of the dye in these two systems follow a similar pathway. Based on these results, both systems are highly efficient for the oxidation of C.I. Reactive Blue 182 dye and represent promising low-cost methods for the degradation of this dye in aqueous solutions.