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United States Department of Agriculture

Agricultural Research Service

Research Project: PRACTICES TO PROTECT WATER QUALITY AND CONSERVE SOIL AND WATER RESOURCES IN AGRONOMIC AND HORTICULTURAL SYSTEMS IN THE NORTH CENTRAL US

Location: Soil and Water Management Research

Title: Nanohybrids of Mg/Al layered double hydroxide and long-chain (C18) unsaturated fatty acid anions: Structure and sorptive properties

Authors
item Celis, Rafael -
item Adelino, M. Angeles -
item Gamiz, Beatriz -
item Hermosin, M. Carmen -
item Koskinen, William
item Cornejo, Juan -

Submitted to: Journal of Applied Clay Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 31, 2014
Publication Date: April 28, 2014
Citation: Celis, R., Adelino, M., Gamiz, B., Hermosin, M., Koskinen, W.C., Cornejo, J. 2014. Nanohybrids of Mg/Al layered double hydroxide and long-chain (C18) unsaturated fatty acid anions: Structure and sorptive properties. Journal of Applied Clay Science. Available at: http://dx.doi.org/10.1016/j.clay.2014.03.026.

Interpretive Summary: Organo-anionic clay complexes were characterized as sorbents for the removal or immobilization of organic pollutants in the environment. Long-chain unsaturated fatty acid anions were incorporated into anionic clays and the resultant organo-LDH nanohybrid materials were characterized and subsequently evaluated as sorbents of six pesticides (clopyralid, imazethapyr, diuron, atrazine, alachlor, and terbuthylazine). All organo-anionic clays displayed higher affinity to uncharged pesticides as compared to unmodified anionic clays, but double bonds in the fatty acid alkyl chain, reduced the affinity of the organo-anionic clays to all pesticides. Two important environmental implications can be derived from these results. First, they demonstrate that subtle differences in the structural properties of the organic anion used as a modifier of anionic clays can strongly affect the performance of the resultant nanohybrid as a sorbent of organic pollutants. Second, they are a direct evidence of the increasing realization that not only the amount, but also the chemical characteristics of organic matter, can influence the sorption properties of organomineral soil colloids questioning the validity of previous universal relationships commonly used to predict the sorption of hydrophobic organic compounds in soils. Scientists now have information to design optimum sorbents to reduce potential movement of organic contaminants to ground water.

Technical Abstract: Long-chain (C18) unsaturated fatty acid anions, elaidate (ELA), oleate (OLE), linoleate (LINO), and linolenate (LINOLEN), were intercalated into Mg/Al (3:1) layered double hydroxide (LDH) and the resultant organo-LDH nanohybrid materials were characterized and subsequently evaluated as sorbents of six pesticides (clopyralid, imazethapyr, diuron, atrazine, alachlor, and terbuthylazine). The effect of the degree (18:1, 18:2, 18:3) and type (cis/trans) of unsaturation in the fatty acid alkyl chain on both the structure and sorptive properties of the LDH-unsaturated fatty acid nanohybrids were determined. All fatty acid anions were readily intercalated into the LDH, yielding structures with basal spacing values ranging between 32 Å (LDH-LINOLEN) and 40 Å (LDH-ELA). The bend imposed by the cis geometry of the double bonds present in OLE, LINO and LINOLEN was identified as a major factor determining the arrangement of these anions in the LDH interlayer space. Intercalation of cis-unsaturated fatty acid anions led to less densely packed structures and reduced the interlayer distance of the resultant nanohybrid compared to the structures resulting from intercalation of the linear, trans-unsaturated elaidate anion. All organo-LDHs displayed higher affinity to uncharged pesticides as compared to unmodified LDH, but double bonds in the fatty acid alkyl chain, particularly when present in cis configuration, reduced the affinity of the organo-LDHs to all pesticides, presumably because they led to structures with reduced hydrophobicity as ompared to those resulting from the incorporation of linear organic anions.

Last Modified: 12/19/2014
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