Kinetic investigations on the reduction of azo dyes in absence and presence of micelle forming surfactants

The kinetic studies on the reduction of Ponceau-4R and Ponceau-S by sodium sulphite was studied in the absence and presence of micelle forming surfactants, cetyltrimethylammonium bromide (CTAB) and sodium dodecyl sulphate (SDS). The kinetic studies on the reduction of the dyes in a buffer medium of pH 7.0 revealed that the reaction is first order with respect to the dye and sulphite ion concentrations. Significant rate constant has been derived. A suitable mechanism consistent with the experimental findings has been proposed. CTAB showed inhibitory effect on the reduction of both the dyes and SDS showed no effect. This may be due to dye in the aqueous bulk phase and sulphite ions in the micellar core.