Kinetics and mechanism of oxidation of bromothymol blue by permanganate ion in acidic medium: Application to textile industrial wastewater treatment

Oxidation of Bromothymol Blue (BTB) by oxyanion potassium permanganate as a strong oxidizing agent in acidic solutions using perchloric acid at a constant ionic strength of 1.0 mol dm(-3) has been studied kinetically spectrophotometrically. The order is first-order in [MnO4-]. while a fractional-first-order in both [H+] and [BTB]. The dependency on the hydrogen ion concentration of the rates shows the oxidation reaction is acid-catalyzed. Absence of either Mn-III and/or Mn-IV transient species as involvement species in the oxidation process was confirmed from Mn-II added to the oxidation reaction. Formation of 1:1 intermediate complex formation kinetically was revealed during the rate-determining step. In the slowest step two-electron transfer processes of the inner-sphere form have been proposed. A mechanism of tentative reaction was proposed and explored with respect to kinetic parameters. Identification of the oxidation product revealed the formation of keto-BTB as derivative of bromothymol blue oxidation. The product of oxidation was isolated and identify using elemental analysis and Fourier Transform Infrared (FTIR) spectra. (C) 2020 Elsevier B.V. All rights reserved.