Abstract
The kinetics of the oxidation of aspartic acid by water-soluble form of colloidal manganese dioxide has been studied in acidic perchlorate media. Monitoring the disappearance of the colloidal MnO2 spectrophotometrically at 390 nm has been used to follow the kinetics. The reaction is first-order in both [MnO2] and [aspartic acid] but fractional-order in [HClO4]. The results suggest formation of an adsorption complex between aspartic acid and MnO2. The complex decomposes in a rate-determining step, leading to the formation of a free radical, which again reacts with the colloidal MnO2 in a subsequent fast step to yield the product. The anionic micelles of sodium dodecyl sulfate have no effect on the oxidation rate whereas the rate constant increased with increase in [TX-100] which has been explained in terms of mathematical model proposed by Tuncay et al. A mechanism in agreement with the observed kinetic results is proposed and discussed. Freundlich isotherm is used to explain the adsorption of aspartic acid on colloidal MnO2. Different activation parameters (E-a, Delta H-#, Delta S-#) have been evaluated and discussed.