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United States Department of Agriculture

Agricultural Research Service

Title: Retention of a Ionizable Herbicide by Organic Ion-Modified Mineral Sorbents: Ph Effects

Authors
item Ulibarri, M - CORDOBA UNIV SPAIN
item Celis, R - IRNAS-CSIC SEVILLA SPAIN
item Hermosin, M - IRNAS-CSIC SEVILLA SPAIN
item Carrizosa, M - IRNAS-CSIC SEVILLA SPAIN
item Pavlovic, I - UNIV CORDOBA SPAIN
item Koskinen, William
item Cornejo, J - IRNAS-CSIC SEVILLA SPAIN

Submitted to: Clay International Conference Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: January 21, 2000
Publication Date: N/A

Technical Abstract: We used the imidazolinone herbicide imazamox (pKa1 nearly equal to 2.0, pKa2 nearly equal to 3.9) as a test compound to comparatively evaluate the ability of two montmorillonites, hydrotalcite, and their organoderivatives (organoclays and organohydrotalcites) as potential sorbents for remediation of ionizable pesticides at different pH levels. At the pH of the sorbents (pH greater than 6), the anionic form of the herbicide was highly sorbed b the calcined product of hydrotalcite, HT500, moderately sorbed bv alkylammonium-exchanged montmorillonites, and very little sorbed by pure montmorillonites, hydrotalcite, and alkylsulfate-exchanged hydrotalcite. The irreversibility of sorption was high in organoclays and intermediate in HT500. Imazamox sorption on the organoclays greatly increased at low pH (pH less than 5.5), especially for organoclays with high basal spacings. This is due to partition of the molecular form of the herbicide within the interlayer organic phase associated with the clays. Decreasing pH also resulted in a decrease in the irreversibility of imazamox sorption by the organoclays. Further decrease of pH to levels less than 3 did not result in enhanced sorption by the organoclays, and indicated that cationic imazamox is less sorbed by the organoclavs than molecular imazamox. In contrast, extensive dissolution of the hydroxide structure of hydrotalcite and organohydrotalcites at low pH levels (pH less than 4) limited their use as sorbents in acidic conditions. The results of this study suggest that the diverse sorbents assayed may find application as filters in water decontamination and as supports for slow release formulation of pesticides similar to imazamox.

Last Modified: 10/30/2014
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