Kinetics of Sorption of Pendimethalin on Soil Samples Obtained from the Banks of Rivers Katsina-Ala and

Abstract Kinetics of the sorption of the herbicide, pendimethalin (3,4-Dimethyl-2,6-dinitro-N-pentan-3-ylaniline) on four soil samples obtained from the banks of Rivers Benue and Katsina-Ala, in Central Nigeria was studied by contacting 5.0 g soil samples with 100 mL 7 × 10 −6 M herbicide solution. The sorption was monitored by following the herbicide concentration in the aqueous phase spectrophotometrically at one hour intervals for 5 hours (at 25˚C, 35˚C, 45˚C, 55˚C and 65˚C, respectively). Pseudo-first order kinetics treatment of the data showed that sorption rates as well as the accompanying activation energies were low, indicating that physical adsorption is the operative mechanism for its retention in the soils and that the herbicide tended to reside more in the aqueous phase, which raised its potential to contaminate natural water systems, when applied on the field