Table of Contents
ISRN Soil Science
Volume 2012 (2012), Article ID 159189, 10 pages
http://dx.doi.org/10.5402/2012/159189
Research Article

Sorption of Sulfonamide Antibiotics to Soil Organic Sorbents: Batch Experiments with Model Compounds and Computational Chemistry

1Institute of Land Use, University of Rostock, Justus-von-Liebig Weg 6, D-18059 Rostock, Germany
2Department of Environmental and Soil Chemistry, University of Koblenz/Landau, Fortstrasse 7, D-76829 Landau, Germany
3Department of Soil Science, University of Trier, Behringstrasse 21, D-54286 Trier, Germany

Received 7 December 2011; Accepted 19 January 2012

Academic Editor: K. Noborio

Copyright © 2012 J. Schwarz et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Sorption of the sulfonamide antibiotics sulfanilamide, sulfadimethoxine, and sulfapyridine to model soil organic matter was investigated. Therefore, Fluka humic acid and an enzymatically reacted vanillin oligomer were used in batch experiments at pH 4.5, 6.0, and 7.5. Sorption of the amphoteric sulfonamides was nonlinear and pH dependent. At pH 4.5 and 6.0 sorption to both humic acid and oligomer increased in the order sulfanilamide < sulfapyridine < sulfadimethoxine. This was primarily attributed to the sulfonamides' H-bond donor/acceptor properties. Sorption to the oligomer indicated that in addition to π-π interactions with aromatics phenolic, aldehyde and methoxyl moieties of the oligomer are specific binding sites. Stronger sorption to humic acid than to the oligomer was related to the more complex structure and functional group diversity of humic acid. At pH 7.5 sorption sequence was changed to sulfadimethoxine < sulfanilamide < sulfapyridine, indicating a changed sorption behavior due to different sulfonamide speciation. In part sorption non-reversibility was strong. This was attributed to surface complexation, rate-limiting intra-particle diffusion processes and entrapment of sulfonamides in voids of organic matter. Molecular mechanics (MM+) computational modeling using a DOM-trimer model confirmed that H-bonding and dipole-dipole interactions are crucial for entrapment of sulfonamides in voids of organic matter.