Sorption of the ionizable pesticide imazamox by organo-clays and organohydrotalcites

The ability of two montmorillonites, SWy-2 and SAz-1, one hydrotalcite, HT [(Mg3Al(OH)(8))(2). CO3. 4H(2)O], and some of their organoderivatives (orga noclays and organohydrotalcites) to sorb the ionizable pesticide imazamox ( 2-[4,5-dihydro-4-methyl-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-5-(methoxym ethyl)-3-pyridinecarboxylic acid) was determined at different pH levels to determine their potential use as sorbent materials for ionizable organic po llutants. At the pH of the sorbents (pH 6-7), the anionic form of imazamox predominated and the calcined product of HT (HT500) was found to be the bes t sorbent for imazamox anion. Negligible sorption of imazamox anion was mea sured on the pure clays, on hydrotalcite and organohydrotalcites, whereas s orption on organoclays was moderate and highly irreversible. Decreasing the pH led to a great increase in the sorption capacity of the organoclays, du e to formation of molecular imazamox, which had a great affinity for the in terlayer organic phase of the organoclays. In contrast, extensive dissoluti on of the hydroxide structure of the hydrotalcites at low pH limited their use as sorbent material in acidic conditions.