Co-Authors:
Aharonson, N., Pesticide Chemistry and Residue Research Laboratory, Agricultural Research Organization, Volcani Center, Bet-Dagan, Israel
Kafkafi, U., Pesticide Chemistry and Residue Research Laboratory, Agricultural Research Organization, Volcani Center, Bet-Dagan, Israel
Abstract:
The effect of pH on the adsorption by montmorillonite and kaolinite clays of three benzimidazole derivatives, thiabendazole (TBZ), 2-benzimidazole carbamic acid methyl ester (MBC), and benzimidazole, was investigated. Adsorption isotherms for TBZ and MBC on Ca and Na Wyoming bentonite showed that an increase in the acidity of the suspension resulted in a significant increase in the adsorption of the fungicide to the clay. The shape of the adsorption curves on Ca-bentonite at various pH values resembled simple titration curves with a midpoint 2.5-3.5 pH units above the pKa of the respective fungicides. The midpoint for TBZ on Na-kaolinite was in the vicinity of its pKa. The fungicide MBC did not adsorb on kaolinite clay even at pH 2. These findings suggested adsorption on mineral clay surfaces by protonation of these basic organic molecules. Protonation and adsorption were not directly related to the basicity of the molecule. An increase in CaCl2 concentration resulted in a decrease in the adsorption of the fungicides. Both fungicides were adsorbed in aqueous solutions on MgO and not adsorbed on Al2O3.
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מונוכרום
הדגשת קישורים
חסימת אנימציה
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