Removal of bromothymol blue dye by the oxidation method using KMnO4: Accelerating the oxidation reaction by Ru (III) catalyst

Oxidation is the preferred method that used for the removal of colored toxic dyes from wastewater. Var-ious oxidizing agents such as permanganate ion, chromate ion, ferricyanide ion have been studied kinet-ically to remove these colored dyes from water. In compared to the other oxidizing agents, potassium permanganate is inexpensive, water-soluble, eco-friendly oxidant, and it can be used in acid, alkaline, and neutral conditions. In addition, it has been widely used for treatment of pollutants in drinking wa-ter and waste-water applications for over 50 years. In this work, the kinetics of bromothymol blue (BTB) oxidation by KMnO4 were investigated using a conventional spectrophotometer in neutral solutions. The oxidation reaction rates were accelerated to notable rates by using of Ru (III) as a homogeneous cata-lyst. The pseudo-1st -order model showed a 1st order in terms of both reactant's concentration, and 2nd overall reaction. The kinetic data indicated the founding of a 1:1 intermediate species with the in-tervention of free radicals into the reaction mechanism. At the reaction conditions of [BTB] = 1 x 10 -5 , [MnO4-] = 4 x 10 -4 mol dm-3, and 25 degrees C, the pseudo-first order rate constant values were calcu-lated to be 1.13 x10 -4 s -1 without Ru (III) and 1.66 x10 -4 using Ru(III) as a catalyst (4 x 10 -4 mol dm-3). Considering the kinetic results, a putative the mechanism of the reaction in the stated redox reaction is postulated and examined. Activation parameters without and with using of Ru (III) were calculated.(c) 2022 Elsevier B.V. All rights reserved.