Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/1999
Publication Date: N/A
Interpretive Summary: Contamination of soil and water environments with organic compounds, specifically pesticides, has become an issue. The need to protect and restore contaminated soils and aquifers is stimulating research to look for suitable materials to be used as sorbents, containment barriers, and pollutant stabilizers. Natural clays have very good sorbent properties due to their large specific surface areas. Replacement of natural metals of th clay surface with large organic molecules has been shown to yield organoclays with improved capacity to bind a variety of organic chemicals. Before organoclays can be used in the protection and restoration of soils and waters contaminated with organic pollutants, information is needed on specific sorbent-pesticide interactions, on which there are very few published reports. In the present work, we used the fungicide triadimefon as a test compound to investigate the potential of several organoclays to remove this pesticide from water. The results of this study showed that organoclays may find application as sorbents in soil and water decontamination, however further research is still needed to determine if these types of organoclays would be economically viable for cleanup of contaminated soil and water.
Technical Abstract: We determined the ability of several organoclays (octadecylammonium- and hexadecyltrimethylammonium-exchanged montmorillonite) and organohydrotalcites (dodecylsulfate- and dodecylbenzenesulfonate-exchanged hydrotalcite) to sorb the uncharged pesticide triadimefon [(1-(4- chlorophenoxy)-3,3-dimethyl-1-(1H-1,2,4-triazol-1-yl)2-butanone] to test the potential use of these sorbents for decontamination purposes and as slow release formulations of the pesticide. Interlayered organoclays and organohydrotalcites were at least 6 times more sorptive than the untreated minerals. Triadimefon sorption was higher on paraffin-like sorbents (organohydrotalcites and high-charge SA-organoclays) than on bilayered sorbents (low-charge SW-organoclays). The nature and amount of organic ion in the interlayer also influenced triadimefon desorption from the different sorbents. Desorption and spectroscopic studies suggested, in general, weak hydrophobic type interactions between triadimefon and the interlayered organic phase of the organoclays and organohydrotalcites. However, hydrogen bonding between the carbonyl group of triadimefon and the monosubstituted amino group of octadecylammonium-exchanged organoclays reinforced the strength of the interaction and resulted in reduced desorbability from these sorbents. Selecting the interlayer ion appeared, therefore, as a good strategy to control the sorptivity and desorbability of the sorbed pesticide for organoclays and organohydrotalcites. The results showed that organoclays and organohydrotalcites may find application as sorbents in soil and water decontamination and as supports for slow release formulation of pesticides similar to triadimefon.