ADSORPTION OF HYDROPHOBIC ORGANIC COMPOUNDS CONTENT IN WATER BY USING MICELLE-CLAY SYSTEMS

Xenobiotics are increasingly being used in agriculture to enhance food production. An excessive application of herbicides, fungicides and different hydrophobic organic compounds is a matter of environmental concern because these chemicals are recognized as a source of potential adverse impact. Many agrochemicals are mobile in soil and readily migrate into ground water compromising water quality. The clean-up of contaminated groundwater by using micelle-clays has become a major focus of research and policy debate in a variety of environmental settings. Thanks to increased adsorption properties, micelle-clay systems have the potential to remove many and different contaminants. Despite to several promising applications available in literature [1,2] water decontamination from pesticides has only received few attempts. The aim of our research was to test the capability of a micelle-clay system for removing two herbicides from water. We obtained a micelle –clay system by using a Wyoming SWy-2-Na-montmorillonite (MMT), supplied by the Clay Minerals Society, and octadecyl-trimethylammonium- bromide (ODTMA) as surfactant. The method adopted for the preparation of organo-modified clay was similar to that described in the literature [3,4]. At first, pure water spiked with atrazina, an old herbicide, was used as sorption model. Successively, an investigation was performed using pure water and a ground natural water both added with tribenuron-methyl, a new sulfonylurea herbicide. The basal spacing (d001) of the unmodified and modified clay mineral before and after the herbicides’ adsorption (cleaning procedure) was determined by X-ray diffraction (XRD) while the retention of herbicides by MMT and surfactant modified MMT was measured by LC micro ESI/MS. The results of XRD and mass spectrometric analyses confirmed the efficiency of the retention processes tested on both xenobiotics. The adsorption of atrazine as well as tribenuron-methyl is more efficient on ODTMA-MMT than natural MMT, since the surfaces of the modified clay are more hydrophobic than the natural montmorillonite. With respect to the natural clay, the organoclay was able to strongly retain 53.9% of spiked atrazine and 100% of tribenuron-methyl from natural water used in the experiment. In pure water tribenuron-methyl underwent hydrolysis and the derivative substance was retained too. In conclusion the tested clay mineral modified using quaternary ammonium salts seems suitable for purifying water contaminated by residues of the new sulfonylurea herbicide and partially for eliminating residues of the old herbicide atrazine: a screening for different classes of contaminants will be continued aiming at the implementation of an efficient system of water cleaning.