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

Abstract

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 MnIII and/or MnIV transient species as involvement species in the oxidation process was confirmed from MnII 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.