Adsorption of paraquat and pirimiphos-methyl by montmorillonite modified with tetradecylammonium chloride and intragallery templating method

Adsorption of paraquat and pirimiphos-methyl in water was performed on four adsorbents including montmorillonite (Mt), organoclay (TDA-Mt) from intercalation of Mt with tetradecylammonium chloride, and mesoporous Mt from intragallery templating method (with and without Ti addition). The adsorbents were characterized by X-ray diffraction, N-2 adsorption-desorption, and transmission electron microscopy. Paraquat adsorption isotherms followed Langmuir model and the adsorption capacity was as follows: TDA-Mt> Mt> mesoporous Ti-Mt> mesoporous Mt. The adsorption mechanism on TDA-Mt and Mt might be via ion exchange. The adsorption on mesoporous samples was on the external surface with negative charge. The presence of Ti enhanced the adsorption capacity. Pirimiphos-methyl adsorbed on negative charge of the external surface of Mt samples. The adsorbed amount increased with the initial concentration due to a strong intermolecular interaction.