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

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• 作者：Panagiota Stathi ^{me01791@cc.uoi.gr} ; Konstantinos C. Christoforidis ^{kchristofo@gmail.com} ; Yiannis Deligiannakis ; ^{ideligia@cc.uoi.gr}
• 关键词：Surface Complexation Modeling ; Adsorption ; Al2O3 ; Methyl-Parathion ; Fenthion ; Methidathion ; Pesticides ; Carbonates ; CO2 ; DFT
• 刊名：Geoderma
• 出版年：2011
• 出版时间：December, 2011
• 年：2011
• 卷：169
• 期：Complete
• 页码：13-19
• 全文大小：787 K

文摘

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-HCO₃^{?/sup>] is formed in solution. At pH 5-7, the convolution of the pH-dependence of the [pesticide-HCO₃?/sup>] concentration with the pH-dependent concentration of the {?#xA0;XOH₂+} sites of a-Al₂O₃ 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 -CH₃ groups. Thus the combination of -CH₃ and S is ultimately responsible for the charge imbalance on these pesticides.}