Interaction of Fluazifop with Al-, Fe³⁺-, and Cu²⁺-Saturated Montmorillonite

Abstract

Abstract--The adsorption of the pesticide Fluazifop, (RS)-2-[4-[[(5-trifluoromethyl)-2-pyridinyl]oxy]phenoxy] propanoic acid, on homoionic Cn2+-, Fe3 +-, and Al-bentonites was investigated by infrared and electron spin resonance spectroscopy. For comparison, the binary complexes of the acid containing the above ions were prepared and characterized. On the whole, the results show that the interaction of the acid with the clay may have involved both the protonation of the pyridine nitrogen atom, due to a proton transfer from the acid metal-bound water, and the formation of direct bonds between the carboxylate groups and the exchange cations. The extent of these interactions was dependent on the nature of the metal ions, the Cu ions being more effective in producing CHC13-extractable neutral carboxylate complexes, while AI and Fe favored the formation of species bearing protonated nitrogen atoms and undissociated carboxyl groups.

Adsorption Mechanisms of Imazamethabenz-Methyl on Homoionic Montmorillonite

“…Such an interaction is expected to lower the force constant of the carbonyl group and decrease the frequency value to a greater extent the higher the polarizing force. A similar behavior was already observed for the adsorption of a number of pesticides on clays (Micera et al 1988, Pusino et al 1989, Bosetto et al 1993.…”

Interaction of Diclofop and Diclofop-Methyl with Al3+-, Fe3+-, and Cu2+-Saturated Montmorillonite

“…Thus, in a soil they may be released into the environment. Similar behavior was observed by Micera et al (1988) and Pusino et al (1989). Thus, the solubility of metal-pesticide complexes may be one of the factors governing both metal and pesticide cycling in soil.…”

“…The ESR spectra of Cu 2+-clay confirmed the absence of direct interaction between metal ions and adsorbed ester, because they showed the signals of the immobilized aqua-ions. These ESR signals were similar to those observed on Cu 2+-clays after dehydration at 120~ or after sorption of hydrophobic, non-coordinating compounds, e.g., the butyl ester of fluazifop (Micera et aL, 1988).…”

“…The ESR spectrum of the copper complex (gll = 2.39, g_l_ = 2.07, and zerofield splitting D = 0.36 cm -~, see Figure 1) is typical of dinuclear complexes in which two metal ions are bridged by four carboxylate groups, as in the wellknown compound copper(II) acetate (Brown and Chidambaram, 1973). A similar structure was previously found for the Cu 2 § complex of fluazifop (Micera et aL, 1988). Carboxylate coordination was also found for the A13 § and Fe 3+ complexes, inasmuch as the 1745-cm -~ absorption band for the undissociated carboxyl group of the free ligand was absent in the IR spectra of all complexes ( Figure 2 and Table 2).…”

Interaction of aminotriazole with montmorillonite and Mg-vermiculite at pH 4

“…This is the only case in which the complex was similar to that obtained by treating montmorillonite at pH 4. There are other cases in which coordination strength of a pesticideclay complex is directly correlated to the polarizing power of the interlamellar cation (Micera et al, 1988;Bosetto et al, 1993). The amount of pesticide adsorbed by montmorillonite was calculated from the interlamellar N and C content to be 71 mEq/100 g, which comprises ~91% of the CEC of this sample (78.2 mEq/100 g).…”