FTIR SPECTROSCOPIC STUDY OF S-METOLACHLOR SORPTION ON INORGANIC AND ORGANICALLY MODIFIED MONTMORILLONITE FROM BOGOVINA

Environmental problems related to the application of herbicides are causing a concern due to their increasing presence in soil, groundwater and surface water. Numerous methods have been developed in order to reduce herbicide mobility and protect natural water resources. The results presented in this paper show the interaction of herbicide S- metolachlor with inorganic and organically modified montmorillonite from Bogovina (Boljevac municipality, Serbia). Clay sample from Bogovina represents Ca-Na montmorillonite with a small amount of quartz, cristobalite and carbonate minerals. Organic montmorillonites were obtained after modification with different concentrations of organic complex (HDTMA and PTMA), whereas inorganic modification was performed with 1M NaCl solution. The interaction between minerals and herbicide was monitored using infrared spectroscopy. IR bands observed in the inorganic modified montmorillonite (Na-montmorillonite) are typical for smectites with a high Al content in the octahedron position. The intercalation of HDTMA+ cations into the interlayer space produces redshift of the IR bands that originate from the vibrations of the adsorbed water, as a consequence of the hydrogen bond strength reduction in HDTMA-montmorillonite. Also, the intensity of these bands decreases significantly with the increasing concentration of HDTMA+ cation. All these changes are related to the decreasing of the water content in the interlayer space by increasing the content of HDTMA. The occurrence of the stretching CH2 vibrations is generally the main difference in the spectrum of HDTMA modified montmorillonite in comparison with the spectrum of inorganically modified montmorillonite. The wavenumber, intensity and width of these bands are sensitive to conformation in hydrocarbon chains. After the organic modification of the montmorillonite with the PTMA complex, stretching vibrations of the phenyl ring occurred. Analysis of FTIR spectroscopy data showed that the hydroge