The adsorption of the herbicide imazamethabenz-methyl, a mixture of the two isomers methyl (+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-4-methylbenzoate (para isomer) and methyl(+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methylbenzoate (meta isomer), from water onto Al3+-, Fe3+-, Ca2+-, K+- and Na+-montmorillonite was studied by analytical (HPLC) methods. The adsorption from an organic solvent was also investigated by spectroscopic (IR) and X-ray diffraction measurements. It was observed that, depending on the acidic properties of the exchangeable cations, two different mechanisms may take place. The first one, acting on Fe3+- and Al3+-clays, involves the protonation of the more basic nitrogen atom of imidazolinone ring of the herbicide because of a proton transfer from the acidic metal-bound water, followed by adsorption on the clay surfaces. In this case, the clay surfaces have greater affinity for the meta than the para isomer, due to the extra-stabilization of the meta protonated form by resonance. The second mechanism, taking place on Ca2+-, K+- and Na+-clays, is hydrogen-bond formation between the ester carbonyl group of the herbicide and hydration water metal ions and is not affected by the structure of the isomers.

ADSORPTION MECHANISMS OF IMAZAMETHABENZ-METHYL ON HOMOIONIC MONTMORILLONITE / Pusino, Alba; Gelsomino, A; Gessa, C.. - In: CLAYS AND CLAY MINERALS. - ISSN 0009-8604. - 43:3(1995), pp. 346-352. [10.1346/CCMN.1995.0430309]

ADSORPTION MECHANISMS OF IMAZAMETHABENZ-METHYL ON HOMOIONIC MONTMORILLONITE

PUSINO, Alba;
1995-01-01

Abstract

The adsorption of the herbicide imazamethabenz-methyl, a mixture of the two isomers methyl (+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-4-methylbenzoate (para isomer) and methyl(+/-)-2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-methylbenzoate (meta isomer), from water onto Al3+-, Fe3+-, Ca2+-, K+- and Na+-montmorillonite was studied by analytical (HPLC) methods. The adsorption from an organic solvent was also investigated by spectroscopic (IR) and X-ray diffraction measurements. It was observed that, depending on the acidic properties of the exchangeable cations, two different mechanisms may take place. The first one, acting on Fe3+- and Al3+-clays, involves the protonation of the more basic nitrogen atom of imidazolinone ring of the herbicide because of a proton transfer from the acidic metal-bound water, followed by adsorption on the clay surfaces. In this case, the clay surfaces have greater affinity for the meta than the para isomer, due to the extra-stabilization of the meta protonated form by resonance. The second mechanism, taking place on Ca2+-, K+- and Na+-clays, is hydrogen-bond formation between the ester carbonyl group of the herbicide and hydration water metal ions and is not affected by the structure of the isomers.
1995
ADSORPTION MECHANISMS OF IMAZAMETHABENZ-METHYL ON HOMOIONIC MONTMORILLONITE / Pusino, Alba; Gelsomino, A; Gessa, C.. - In: CLAYS AND CLAY MINERALS. - ISSN 0009-8604. - 43:3(1995), pp. 346-352. [10.1346/CCMN.1995.0430309]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11388/49132
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