Adsorption of Pesticides from Water by Functionalized Organobentonites

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• 作者：Marta Cruz-Guzmá ; n ; Rafael Celis ; M. Carmen Hermos&iacute ; n ; William C. Koskinen ; and Juan Cornejo
• 刊名：Journal of Agricultural and Food Chemistry
• 出版年：2005
• 出版时间：September 21, 2005
• 年：2005
• 卷：53
• 期：19
• 页码：7502 - 7511
• 全文大小：184K
• 年卷期：v.53,no.19(September 21, 2005)
• ISSN：1520-5118

文摘

Replacement of natural inorganic cations of clay minerals with organic cations has been proposedas a strategy to improve the adsorptive capacity of clay minerals for organic compounds, includingpesticides. The organic cations most commonly used for this purpose have been quaternaryammonium ions containing alkyl or aryl chains without specific functional groups. In this work, weevaluated the ability of two bentonites (SWy-2 and SAz-1) exchanged with four natural organic cationscontaining diverse functional groups (L-carnitine, L-cysteine ethyl ester, L-cystine dimethyl ester, andthiamine) as adsorbents of pesticides varying in their chemical structures (simazine, hexazinone,triadimefon, alachlor, carbaryl, and imazethapyr). For comparison purposes, the adsorptive propertiesof two "classical" organobentonites, hexadecyltrimethylammonium- and phenyltrimethylammonium-exchanged bentonites, were also determined. Most organobentonites displayed higher affinity forthe pesticides than the untreated bentonites, but the improvement in adsorption capacity varieddepending on the characteristics of the pesticide and the interlayer organic cation. Triadimefon,carbaryl, and imazethapyr displayed the highest affinity for carnitine (K_f = 229-2377)-, thiamine (K_f= 83-354)-, and cystine (K_f = 96-100)-treated bentonites, respectively, whereas alachlor wasadsorbed similarly by all organobentonites. In general, pesticide adsorption-desorption hysteresiswas greater for adsorbents with the highest adsorption capacities. The results demonstrate thatselective modification of smectitic clay minerals with natural organic cations containing appropriatefunctional groups can be a useful strategy to improve their performance for the removal of specificpesticides from the environment.Keywords: Bentonites; organoclays; adsorption; pesticides