7th International Chemistry Symposium
SIQ 2019
Chlordecone (CLD) and hexachlorocyclohexane (HCH) are synthetic organochlorine compounds classified as persistent organic pollutants by the Stockholm Convention. When the technical HCH is used, β-hexachlorocyclohexane (β-HCH) is the most persistent isomer. Due to the persistence of these pollutants in the environment, the drinking water production plants have been equipped with filters of activated carbon (AC). In the present work, a theoretical study to evaluate the interaction between CLD and β-HCH with basic surface groups (SG) of AC, considering pH and hydration effect, was done, in order to better understand the adsorption process. Coronene was selected as AC model for the simulation of pesticides interaction with basic functional groups (primary, secondary and tertiary amine) attached to the edge of the coronene. Energetic and geometrical aspects of the interactions between CLD and β-HCH with SG on AC are analyzed by Multiple Minima Hypersurface methodology (MMH) using the semi-empirical Hamiltonian PM7. Furthermore, 16 distinctive structures obtained by MMH were re-optimized by Density Functional Theory, using the functional M06-2X and more rigorous characterized by Quantum Theory of Atoms in Molecules. As results, a greater association of both pesticides with the primary amine in comparison with the others, in the absence and presence of water molecules, was observed. Moreover, it was observed a weak association of the pollutants with the basic SGs. The interactions have dispersive nature between the chlorine atoms of the pesticides and the π-cloud of the functionalized coronene, evidencing a mechanism of physisorption of both pollutants in the basic ACs studied.
Chlordecone (CLD) and hexachlorocyclohexane (HCH) are synthetic organochlorine compounds classified as persistent organic pollutants by the Stockholm Convention. When the technical HCH is used, β-hexachlorocyclohexane (β-HCH) is the most persistent isomer. Due to the persistence of these pollutants in the environment, the drinking water production plants have been equipped with filters of activated carbon (AC). In the present work, a theoretical study to evaluate the interaction between CLD and β-HCH with basic surface groups (SG) of AC, considering pH and hydration effect, was done, in order to better understand the adsorption process. Coronene was selected as AC model for the simulation of pesticides interaction with basic functional groups (primary, secondary and tertiary amine) attached to the edge of the coronene. Energetic and geometrical aspects of the interactions between CLD and β-HCH with SG on AC are analyzed by Multiple Minima Hypersurface methodology (MMH) using the semi-empirical Hamiltonian PM7. Furthermore, 16 distinctive structures obtained by MMH were re-optimized by Density Functional Theory, using the functional M06-2X and more rigorous characterized by Quantum Theory of Atoms in Molecules. As results, a greater association of both pesticides with the primary amine in comparison with the others, in the absence and presence of water molecules, was observed. Moreover, it was observed a weak association of the pollutants with the basic SGs. The interactions have dispersive nature between the chlorine atoms of the pesticides and the π-cloud of the functionalized coronene, evidencing a mechanism of physisorption of both pollutants in the basic ACs studied.
About The Speaker
Mr. Chayan Carmenate