ARS | Publication request: Removal of Pesticides from Water by Biomolecule-Exchanged Clays

Submitted to: International Association Of Environmental And Analytical Chemistry
Publication Acceptance Date: May 19, 2004
Publication Date: August 16, 2004
Citation: Cruz-Guzman, M., Celis, R., Hermosin, M.C., Koskinen, W.C., Cornejo, J. 2004. International Association Of Environmental Analytical Chemistry Abstracts. International Association Of Environmental And Analytical Chemistry. P. 53.

Technical Abstract: Replacement of natural inorganic cations of clay minerals with organic cations through ion exchange reactions has been proposed as an strategy to improve the adsorptive capacity of clay minerals for organic compounds, including pesticides. The organic cations most commonly used for this purpose have been quaternary ammonium ions, containing alkyl or aryl chains, without specific functional groups. In this work, we evaluated the ability of montmorillonite exchanged with four natural organic cations containing diverse functional groups (L-carnitine, L-cysteine ethyl ester, L-cystine dimethyl ester, and thiamine) as sorbents of pesticides varying in their chemical structures (i.e., alachlor, triadimefon, imazethapyr, and carbaryl). The organic cations were selected on the basis of i) their natural origin, which should reduce concern about the incorporation of these materials into soil and aquatic environments compared to the classical alkyl- and aryl-ammonium cations, and ii) the presence of diverse functional groups in their structures, with the aim to establish relationships between pesticide sorption and the structural characteristics of both the organic cation and the sorbing pesticide. Most organoclays displayed higher affinity for the pesticides than the untreated clay, but the improvement in sorption capacity varied with the characteristics of the pesticide and the interlayer organic cation. Thus, triadimefon, imazethapyr, and carbaryl displayed the highest affinity for carnitine, cystine, and thiamine, respectively, whereas alachlor was sorbed similarly by all organoclays. Relationships between sorption and the nature of the pesticides and the organoclays are discussed. The results demonstrated that selective modification of smectitic clay minerals with natural organic cations containing appropriate functional groups can be a useful strategy to improve the performance of organoclays for the removal of specific pesticides from the environment.