The adsorption of herbicides and pesticides on clay minerals and soils. Part 2. Atrazine

The adsorption of atrazine and two model compounds, 2-chloropyrimidine and 3-chloropyridine on clay minerals ( bentonite, montmorillonite and kaolinite), organic matter ( humic acid) and soil ( with and without organic matter) has been studied using FT-infrared spectroscopy (IR), thermogravimetric analysis (TGA), high pressure liquid chromatography ( HPLC) and X-ray diffraction (XRD). 3-Chloropyridine, 2-chloropyrimidine and atrazine were adsorbed through hydrogen bonding on bentonite, montmorillonite, humic acid and soil. In addition to hydrogen bonding, protonation of 3-chloropyridine and atrazine was also observed. In the adsorption of 2-chloropyrimidine on bentonite and montmorillonite an ion exchange mechanism also occurred. No adsorption of 3-chloropyridine or 2-chloropyrimidine was observed on the kaolinite clay mineral. Both the clay minerals and organic matter of soil contribute to the adsorption of organic compounds on soil but the clay minerals bentonite and montmorillonite play a major role in their adsorption on soil.