ATRAZINE INTERACTIONS WITH CLAY-MINERALS - KINETICS AND EQUILIBRIA OF SORPTION

A novel technique using on-line microfiltration and HPLC analysis has been used to study sorption kinetics and sorption equilibrium of the herbicide atrazine with the clay minerals montmorillonite, kaolinite, and illite and the clay fraction of a soil. Fast and slow labile sorption have been observed for atrazine along with a reversible but kinetically slow sorption/desorption process that is consistent with diffusion of pesticide into the interior of the clay particles. Labile sorption capacity, mole fraction site coverage, labile sorption equilibrium function, and distribution coefficient were determined for the clay minerals in aqueous slurries with atrazine. The identification and quantitative descriptions of key chemical species avoid some of the commonly reported hysteresis problems. Distribution coefficients are derived from the equilibrium constants so that comparisons may be made with the results of other workers.