Degradative treatment of bispyribac sodium herbicide from synthetically contaminated water by colloidal MnO2 dioxide in absence and presence of surfactants.

Bispyribac sodium (BS) is one of the most commonly used herbicides used to kill selectively unwanted herbs particularly in rice plantation. However, the increasing use of herbicides in agricultural field is associated with a potential risk to water resources and aquatic system. Thus the treatment of such pesticides, after fulfillment of their herbicidal activity is of quite interest to minimize the contamination of water. The degradation kinetics of BS from synthetic contaminated water by water soluble colloidal MnO2 in acidic medium (HClO4) has been studied spectrophotometrically in the absence and presence of different surfactants. The degradation has been observed to be fractional-order in both BS and HClO4 under pseudo-first-order reaction condition with respect to MnO2. The anionic surfactant (sodium dodecyl sulfate) has been observed to be ineffective whereas the cationic surfactant (cetyltrimethyl ammonium bromide) causes flocculation with oppositely charged colloidal MnO2 and therefore could not be studied further. However, the non-ionic surfactant (Triton X-100) has been observed to accelerate the reaction rate. The catalytic effect of this surfactant has been analyzed and discussed in the light of the available mathematical model. The kinetic data have been used to generate the various activation parameters accompanying the degradation process of BS in the absence and presence of the non-ionic surfactant, Triton X-100.