Oxidative decolorization of methyl red dye with chloramine-T ─ Kinetic and mechanistic chemistry

Abstract

<span style="font-size:9.0pt;mso-bidi-font-size: 12.0pt" lang="EN-GB">A simple and expeditious oxidative decolorization technique has been developed for the removal of Methyl Red dye (MR; C.I. Acid Red 2) present in the wastewater. The kinetic and mechanistic aspects of the present redox system have also been investigated. Kinetics and oxidative decolorization of MR dye with sodium N-chloro-<i style="mso-bidi-font-style:normal">p</i>-toluenesulfonamide or chloramine-T (CAT) in HClO₄ medium at 303 K has been investigated spectrophotometrically at λ_max 524 nm. The reaction shows a first-order dependence of rate each on [CAT]_o and [MR]_o. The reaction is catalyzed by [HClO₄] and the order with respect to [H⁺] is found to be fractional (0.75). Activation parameters have been evaluated. The oxidation products of MR dye are identified as <i style="mso-bidi-font-style:normal">N</i>-(4-dimethylamino-phenyl)-hydroxylamine and 4-nitroso-benzoic acid by GC-MS analysis. The observed results have been explained by a plausible mechanism and the related rate law is deduced. Further, the present redox system can be adopted for treating MR dye present in industrial effluents with suitable modifications to reduce the toxicity caused by MR dye.

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