An investigation on the sorption behaviour of montmorillonite for selected organochlorine pesticides from water.

The sorption behaviour of montmorillonite towards organochlorine pesticides (OCPs) from aqueous solutions is reported. After preliminary investigation of the sorption capability of clay for selected OCPs, aldrin was used as a model compound for further experiments. The batch sorption experiments were carried out as functions of contact time, pH of the solution, initial aldrin concentration and dosage of the montmorillonite. After traditional liquid-liquid extraction, the determination of OCPs was carried out by gas chromatography coupled with a micro-electron capture detector (GC-microECD). The results indicated that sorption of aldrin followed the second-order kinetic model and that the equilibrium time depended on the initial aldrin concentration. The film diffusion was found to be a main sorption rate control mechanism. The removal was explained according to the electrostatic bonding mechanism. The Freundlich isotherm model better represented the sorption data than the Langmuir model. The montmorillonite was also used efficiently for the removal of OCPs from fortified tap and surface (lake) water samples.