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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 30, Number 9
BKCSDE 30(9)
September 20, 2009 

Kinetics Study of Malachite Green Fading in the Presence of TX-100, DTAB and SDS
Babak Samiey*, Ali Raoof Toosi
Classical model, Malachite green, Kinetics, Fading, Surfactant
The rate constants of alkaline fading of malachite green (MG+) was measured in the presence of nonionic (TX-100), cationic (DTAB) and anionic (SDS) surfactants. This reaction was studied under pseudo-first-order conditions at 283∼303 K. The rate of fading reaction showed noticeable dependence on the electrical charge of the used surfactants. It was observed that the reaction rate constants were increased in the presence of TX-100 and DTAB and decreased in the presence of SDS. According to Hughs-Ingold rules for nucleophilic substitution reactions, the electric charge of MG/surfactant compound along with decrease in dielectric constant of MG+ micro-environment in this compound varies the rate of fading reaction. Binding constants of surfactant molecules to MG+ were calculated using cooperativity, pseudo-phase ion exchange and classical models and the related thermodynamic parameters were obtained by classical model. The results show that the binding of MG+ to TX-100 is exothermic and binding of MG+ to DTAB and SDS in some concentration ranges of the used surfactants is endothermic and in the other ones is exothermic.
2051 - 2056
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