Mechanistic investigation of osmium(VIII)catalyzed oxidation of brilliant green dye by chloramine-T in alkaline medium: a spectrophotometric kinetic study

Wastewater generated by dyeing industries is of great threat to the globe and is major area of concern. In present paper, we deals with oxidation of brilliant green (BG) by catalytic route in alkaline medium at 298 K. Osmium( VIII) used as catalyst and the reaction showed first-order and zero-order behavior with respect to [BG] and [CAT] respectively. The reaction followed fractional-order kinetics with respect to [NaOH] and [Os(VIII)]. Negligible effect of [Cl-], [PTS] and ionic strength of the medium on the rate of oxidation have also been noted. Decrease in the rate of reaction with decrease in the dielectric constant of the medium was also observed. Comparative studies between catalyzed and uncatalyzed reaction have also been reported. It is found that catalyzed reaction is four fold faster than uncatalyzed reaction. Activation parameter and catalytic constant (K-C) have also been calculated at different temperatures. GC-MS analysis identified the oxidation products of the BG i.e. N, N-diethylaminobenzophenone and p-N, N-diethylamino phenol while the stoichiometry of the reaction was found to be 1:1. On the basis of kinetic results, a plausible mechanism has been proposed and verified.