Degradation of acephate by colloidal manganese dioxide in the absence and presence of surfactants

Abstract

The kinetics of the degradation of acephate by water-soluble colloidal MnO₂ in acidic medium (HClO₄) has been studied spectrophotometrically in the absence and presence of surfactants. The experiments have been performed under the pseudo-first-order reaction conditions with respect to MnO₂. The degradation has been observed to be fractional order with respect to acephate and HClO₄ while first order with respect to MnO₂ in the absence and presence of surfactants. It has been observed that cationic surfactant, cetyl trimethyl ammonium bromide, causes flocculation with oppositely charged colloidal MnO₂ whereas anionic surfactant, sodium dodecyl sulfate, has no considerable effect on the reaction kinetics. However, non-ionic surfactant, Triton X-100 (TX-100) accelerates the reaction rate. The catalytic effect of TX-100 has been discussed in the light of the available mathematical model. The kinetic data have been used to calculate the different activation parameters for the oxidative degradation of acephate by colloidal MnO₂.

Keywords:

• Degradation
• Acephate
• Manganese dioxide
• Pseudo-first-order
• Surfactants
• TX-100

Acknowledgments

The authors are grateful to the Chairman, Department of Applied Chemistry, Faculty of Engineering and Technology, Aligarh Muslim University for providing necessary laboratory facilities. One of the authors (Qamruzzaman) is also thankful to the University Grants Commission, New Delhi for the award of Maulana Azad National Fellowship.