Submicellar catalytic effect of cetyltrimethylammonium bromide in the oxidation of ethylenediaminetetraacetic acid by MnO4−

The effects of cetyltrimethylammonium bromide (CTAB), sodiumdodecyl sulphate (SDS) and Triton X-100 (TX-100) on the oxidative degradation of ethylenediaminetetraacetic acid (EDTA) by MnO4− have been studied spectrophotometrically at 525 and 420 nm, respectively. It was found that cationic surfactant catalyse the reaction rate while anionic and non-ionic have no effect. The premicellar environment of CTAB strongly catalyses the reaction rate which may be due to the favorable electrostatic binding of both reactants (MnO4− and EDTA) with the positive head groups of the CTAB aggregates. The influence of different parameters such as [MnO4−], [EDTA], [H+] and [surfactants] were also considered. The reaction follows the first- and fractional-order kinetics with respect to [MnO4−] and [EDTA]. The proposed mechanism and the derived rate law are consistent with the observed kinetics.