Kinetics and Mechanism of Fading of Victoria Blue Dye in Alkaline Medium

LD Felix, degoke Adesoji Adesoji

Abstract


The kinetics of fading of Victoria Blue (VB) in sodium hydroxide was studied spectrophotometrically via pseudo-first order kinetics at 616nm with the view to ascertaining the rate of reaction and possibly to propose a plausible mechanism for the reaction . The reaction showed first order dependence with respect to [VB] and also first order to  [OH-]. Michaelis-Menten plot suggested the presence of an intermediate complex. The presence of +1 and -1 charges on the reactant ions at the rate determining step was shown by the ionic strength dependence. The activation energy (Ea), ΔH‡, ΔS‡  , ΔG‡  were 52.32 kJmol-1, 50.14 kJmol-1, -0.13 kJK-1mol-1, 88.88 kJmol-1 respectively. Stoichiometric result indicated that one mole of Victoria blue dye consumed one mole of the hydroxyl ion in solution. Product analysis revealed carbinol as the major reaction product. A plausible mechanism in consonance with the kinetic and spectroscopic data was proposed. 

Keywords: Victoria Blue(VB), Sodium hydroxide, Potassium nitrate, Absorbance(A) Fading, Kinetics and Mechanism 


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Chemical Society of Nigeria