Adsorption Kinetics of Fluroxypyr Herbicide in Aqueous Solution onto Granular Activated Carbon

Fluroxypyr is a widely used herbicide whose presence in natural waters has prompted research into its removal by adsorption. This article reports a kinetics study of fluroxypyr adsorption on a commercial activated carbon. The experimental study used a micro differential column batch reactor operated at three solution flow rates and two initial fluroxypyr concentrations, establishing a differential regime in order to obtain correct experimental data. Initial rates at zero coverage permitted the external transfer coefficient k(L) to be calculated. Internal surface diffusion coefficients D-S were determined by using the Homogeneous Surface Diffusion Model running the FAST software and taking advantage of tabulated user-oriented solutions. This model satisfactorily fits the experimental data. DS values were 2.5 x 10(-14) and 4.2 x 10(-14) m(2) s(-1) for initial concentrations of 30 and 50 mg/L, respectively. These values were confirmed by experiments in a widely used shaken batch reactor with a determined kL value.