ADSORPTION OF HYDROPHOBIC ORGANIC COMPOUNDS ONTO A GEOSORBENT MATERIAL

Xenobiotics are increasingly used in agriculture to enhance food production. Excessive applying of these products (as herbicides, fungicides, different pesticides) is a matter of environmental concern because these chemicals are recognized as a source of potential adverse impact. Many of these chemicals are mobile in soil and readily migrate into ground water to compromise water quality. Cleanup of contaminated groundwater using organo-clays has become a major focus of research and policy debate in a variety of environmental settings. Organo-clay complexes have the potential to remove heavy metals and organic pollutants thanks to increased adsorption properties. These complexes show several promising applications in contamination prevention and environmental remediation, including the treatment of waste effluents, as extenders for activated carbon and as components of clay barriers, for example in clay slurry walls, hazardous waste landfills and petroleum tank forms. The aim of our research was to develop a matrix capable of removing organic contaminants from water to be purified. Modified organo-clay was obtained using SWy-2-Na-montmorillonite (Wyoming) and octadecyl-trimethyl-ammonium-bromide (ODTMA) as surfactant. The montmorillonite (MMT) used in this study was supplied by the Clay Minerals Society. The chemical composition of MMT is: SiO2 62.9%, Al2O3 19.6%, Fe2O3 3.35%, MgO 3.05%, CaO 1.68%, Na2O 1.53%. The formula of MMT is (Ca0.12 Na0.32 K0.05)[Al3.01 Fe(III)0.41 Mn0.01-Mg0.54 T 0.02][Si7.98 Al0.02]O20 (OH)4, as calculated from its chemical composition. The cation exchange capacity (CEC) is 76.4 cmol+ Kg-1. At first, simulated water polluted by atrazina, an old xenobiotc, was used as sorption model at rate of 0.35 mol Kg-1. Successively, a river water as real sample containing chloroform, dichloromethane and dibrochloromethane was treated. The method adopted for the preparation of the organo-modified clay was similar to that described in the literature. Basal spacing (d001) of the unmodified and modified clay mineral was determined by X-ray diffraction (XRD), following drying at 25°C. XRD patterns were recorded by CuK radiation and a Rigaku Geigerflex RAD3-C automated X-ray diffractometer that employs a goniometer fitted with a h-compensating slit, a 0.15 mm receiving slit, and a diffracted-beam graphite monochromator, from 2° to 10° 2, in steps of 0.02° 2, at 1s per step. Retention by surfactant-modified MMT was measured by using the Thermo micro ESI/FT-ICR/MS 7T. Results of chemical analyses confirmed the usefulness of modified organo-clay adsorbent compared to natural montmorillonite.