Organoclays and organohydrotalcites as sorbents for polar pesticides

The sorption and desorption of the anionic herbicide imazamox (pK(a1) appro ximate to 3.9, pK(a2)approximate to 2.0) by organoclays (alkylammonium-exch anged montmorillonite) and organohydrotalcites (alkylsulfate-exchanged hydr otalcite) was compared with that of the neutral fungicide triadimefon, to t est the potential use of these sorbents for decontamination purposes and sl ow release formulations as related to the charge characteristics of the pes ticide. In general, interlayered organoclays and organohydrotalcites were m uch more sorptive for imazamox and triadimefon than the corresponding natur al or inorganic minerals. Depending on the sorbent, triadimefon sorption on organoclays and organohydrotalcites was 5 to 200 times greater than that o bserved for imazamox anion. In contrast, imazamox sorption to organoclays w as irreversible, whereas triadimefon sorption by the organoclays and organo hydrotalcites was moderate to low. Imazamox sorption, as well:as the revers ibility of the sorption-desorption process, increased with decreasing pH, d ue to protonation and further sorption of molecular imazamox species. The r esults;of this work indicate that the diverse sorbents assayed may find app lication as filters in water decontamination for imazamox anion and as filt ers and supports for slow release formulations in the case of molecular ima zamox and triadimefon.