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

The effects of the anionic surfactant sodium dodecyl sulfate (SDS) on the spatio-temporal and temporaldynamics of the ferroin-catalyzed Belousov-Zhabotinsky (BZ) reaction have been studied over a widesurfactant 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 significantlydepends on the surfactant concentration. The trend of the wave speed V upon the increasing amount of SDSwas found to have a maximum at [SDS] ) 0.075 mol dm-3 (V ) 0.071 mm s-1), after which the speeddecreased to 0.043 mm s-1 at [SDS] ) 0.5 mol dm-3, which is below the value found in the absence of thesurfactant (V ) 0.055 mm s-1). The response of the oscillatory BZ system to the addition of SDS has beenascribed to two different causes: (a) the peculiar capability of the organized surfactant assemblies to affectthe reactivity by selectively sequestering some key reacting species and (b) the modifications induced bySDS on the physical properties of the medium. These hypotheses have been corroborated by performingspectrophotometric investigations on the stirred BZ system. Complementary viscosity measurements gaveuseful hints for the clarification of the surfactant role.