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Heavy Metal Adsorption by Montmorillonites Modified with Natural Organic Cations
Author(s) -
Cruz-Guzmán M.,
Celis R.,
Hermosín M. C.,
Koskinen W. C.,
Nater E. A.,
Cornejo J.
Publication year - 2006
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2005.0131
Subject(s) - chemistry , adsorption , inorganic chemistry , metal , functional group , environmental chemistry , organic chemistry , polymer
Agricultural and industrial pollution release large amounts of heavy metals into the atmosphere, surface water, soil, and plants. The protection and restoration of soils and water contaminated with heavy metals generate a great need to develop efficient adsorbents for these pollutants. This study reports the adsorption of Pb(II) and Hg(II) by two reference montmorillonites, Wyoming (SWy‐2) and Arizona (SAz‐1), that were pretreated with various natural organic cations containing different functional groups (L‐carnitine, L‐cysteine ethyl ester, L‐cystine dimethyl ester, and thiamine cations) and with synthetic, nonfunctionalized organic cations (hexadecyltrimethylammonium [HDTMA] and phenyltrimethylammonium [PTMA] cations). Most of the organoclays adsorbed less Pb(II) than the untreated montmorillonites, with the exception of the L‐carnitine–treated montmorillonites. The carboxyl functional group on L‐carnitine was apparently effective for complexing Pb. In contrast, Hg(II) adsorption was greatly increased by several of the organic cation pretreatments. Sulfur‐containing organic functional groups enhanced Hg(II) adsorption. The synthetic organic cations PTMA and HDTMA suppressed adsorption of Pb(II) and Hg(II) because these organic cations competed with the metals for adsorption sites on the clay surfaces and lack organic functional groups capable of interacting with the heavy metals. These findings are consistent with prior understanding of organic functional group‐metal complexation reactions but go further by demonstrating that organoclays can be selectively functionalized with natural organic cations to enhance their affinity for heavy metals.