A general mechanism of interaction of carbonates with non-polar S-containing pesticides

作者：Stathi Panagiota; Christoforidis Konstantinos C; Deligiannakis Yiannis^*

来源：Geoderma, 2011, 169: 13-19.

DOI：10.1016/j.geoderma.2010.10.022

• Surface Complexation Modeling
• Adsorption
• Al(2)O(3)
• Methyl-Parathion
• Fenthion
• Methidathion
• Pesticides
• Carbonates
• CO(2)
• DFT

Based on a combination of Density Functional Theory (DFT) and Surface Complexation Modeling (SCM), a general mechanism is suggested for (a) the interaction of non-polar S-containing pesticides, Methyl/Ethyl-Parathion, Fenthion, Methidathion, and Thiram with carbonates in solution and (b) their adsorption on chargeable oxides. Surface Complexation Models show that in the presence of carbonates, the species [pesticide-HCO(3)(-)] is formed in solution. At pH 5-7, the convolution of the pH-dependence of the [pesticide-HCO(3)(-)] concentration with the pH-dependent concentration of the { XOH(2)(+)} sites of a-Al(2)O(3) determines the pH profile of the adsorption. The Density Functional Theory calculation for Methyl-Parathion and Thiram reveals that a significant fraction of negative charge is accumulated on the S-atoms of the pesticides while a net positive charge is localized on the -CH(3) groups. Thus the combination of -CH(3) and S is ultimately responsible for the charge imbalance on these pesticides.

• 出版日期2011-12