Spatio-Temporal Perturbation of the Dynamics of the Ferroin Catalyzed Belousov−Zhabotinsky Reaction in a Batch Reactor Caused by Sodium Dodecyl Sulfate Micelles.

Abstract: The effects of the anionic surfactant sodium dodecyl sulfate {(SDS)} on the spatio-temporal and temporal dynamics of the ferroin-catalyzed {BelousovZhabotinsky} {(BZ)} reaction have been studied over a wide surfactant concentration range. For the first time, investigations were performed also for unstirred systems. The presence of {SDS} in the reaction mixture influences the oscillatory parameters to an extent that significantly depends on the surfactant concentration. The trend of the wave speed v upon the increasing amount of {SDS} was found to have a maximum at {[SDS]} = 0.075 mol dm3 (v = 0.071 mm s1), after which the speed decreased to 0.043 mm s1 at {[SDS]} = 0.5 mol dm3, which is below the value found in the absence of the surfactant (v = 0.055 mm s1). The response of the oscillatory {BZ} system to the addition of {SDS} has been ascribed to two different causes: (a) the peculiar capability of the organized surfactant assemblies to affect the reactivity by selectively sequestering some key reacting species and (b) the modifications induced by {SDS} on the physical properties of the medium. These hypotheses have been corroborated by performing spectrophotometric investigations on the stirred {BZ} system. Complementary viscosity measurements gave useful hints for the clarification of the surfactant role.