A kinetic study on the reduction of colloidal manganese dioxide by oxalic acid in different surfactant organized media

MnO₂ is a widely used catalyst in various organic and inorganic reactions in many industries. Most of them are complex and there mechanism of catalysis is acceptable but still not satisfactory. The reduction of MnO₂ by H₂C₂O₄ is a complex reaction. The study of micellar catalysis using cationic, anionic and nonionic surfactants on this reaction may provide the information for proper understanding of its effect and improve our knowledge of micellar catalysis. Kinetics of the reaction between colloidal manganese dioxide and oxalic acid in aqueous solution were studied spectrophotometrically at 390 nm. The reaction was also carried out in   presence of various anionic (sodium dodacylsulphate), cationic (cetyltrimethyl-ammonium bromide) and nonionic (Triton X-100) surfactants. The apparent rate constant was calculated for the reaction of colloidal MnO₂ with oxalic acid in aqueous solution where the surfactant was absent. The calculated rate constant was made an effort to establish the comparison the rate constant of the reaction in different micellar media (micelle of TX-100, SDS and CTAB). The micellar catalysis was used to determine the rate of the reaction with different concentrations of micelle of TX-100, SDS and CTAB. A comparison of catalytic efficiency of three micellar system was made by comparing the rate constants obtained from different micellar system. Finally, the comparison of apparent rate constant without surfactant and in presence of surfactant provided a better understanding of the reduction of manganese dioxide by oxalic acid and vindicated the knowledge base for a complete understanding of the various features of catalysis by micelles of different surfactants.

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