KINETICS OF HYDROGENE PEROXIDE DECOMPOSITION IN ALKALINE MEDIUM IN AQUEOUS SOLUTIONS OF MICELLE FORMING SURFACTANTS

摘要

The kinetics of the H2O2+HOO~- reaction in the presence of micelle forming surfactants (MFS) (anionic-sodium sulphate (DDS) and cationic-dodecyltrimethylammonium bromide (DTAB)) is studied by a gasometric method. It is established that the extent of their influence depends on concentration. At [MFS]0< ccm both surfactants decrease the reaction rate R_(O2) , which is due to the fact that they react with HO~· (HOO~-) free radicals and thus slow down the overall R_O . In the case when [MFS]0>ccm the rate increases. It is assumed that micelles are more favourable medium for the reaction than the water. The study of the reaction kinetics in DDS+DTAB mixture showed that vesicles are more favourable reaction medium. They have structural similarities with inverse micelles. In fact realising the reaction in inverse emulsions a considerable R_O increase is established. To obtain inverse emulsions aerosol OT (AOT) and lecithin are used as emulsi-fiers. Lecithin which is a zwitter-ion type MFS is more effective than AOT. By direct experiments it is established that positively charged 'heads' are more active than the negatively charged.