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10 June 2005 Computational modeling of the adsorption of 2,4-DNT on clay
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Experimental studies have shown that a key factor affecting the bioavailability and biodegradability of nitroaromatic compounds (NAC's) in subsurface environments is their sorption onto clay minerals. This study present the recent ab initio quantum mechanical calculations on the interaction of 2,4-DNT (DNT) with the basal siloxane site surface of kaolinite, a clay mineral. Theoretical calculations of the low energy conformation of DNT interacting with the siloxane site surface of clay minerals were performed in order to obtain their properties adsorbed on soil environments as well as the structure of the adsorbed molecule. The calculations also yielded the way of orientation and the effect of the adsorption. This study was performed using DFT//HF and MP2//HF methods taking into account the contribution of the Coulombic (CEb) and dispersion (DEb) energies, to obtain the binding energies between DNT and siloxane surface. A comparison of the CEb and DEb energies shows that the stabilization of DNT at the siloxane sites, using a small molecular model (single tetrahedra), is mainly provided by dispersion interaction energy. Considering the accuracy and cost of the computation methods the 6-31+G* basis set produced the best representation of the interaction energy (42 kJ/mol) using the MP2//HF level of theory for the DNT-Siloxane surface. These theoretical calculations give a good prediction of the interaction between the 2,4-DNT molecule with soil clay minerals. The computational results are compared with the experimental results obtained with the FT-IR microscopic technique.
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Carmen M. Ramos, Liliana F. Alzate, Yleana M. Colon, Samuel P. Hernandez, and Nairmen Mina "Computational modeling of the adsorption of 2,4-DNT on clay", Proc. SPIE 5794, Detection and Remediation Technologies for Mines and Minelike Targets X, (10 June 2005);


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