TY - JOUR
T1 - Adsorption of zwitterionic fluoroquinolone antibacterials to goethite
T2 - A charge distribution-multisite complexation model
AU - Paul, Tias
AU - Liu, Jinyong
AU - Machesky, Michael L.
AU - Strathmann, Timothy J.
N1 - Funding Information:
This contribution was developed under a STAR Research Assistance Agreement No. 91683701 awarded by the U.S. Environmental Protection Agency to T. Paul. It has not been formally reviewed by the EPA. The views expressed in this document are solely those of the authors and the EPA does not endorse any products or commercial services mentioned in this publication. Financial support was also provided in part by an NSF CAREER award to T.J. Strathmann ( CBET-074645 ). TEM imaging was carried out in the Frederick Seitz Materials Research Laboratory Central Facilities, University of Illinois, which are partially supported by the U.S. Department of Energy under grant DEFG02-91-ER45439 .
PY - 2014/8/15
Y1 - 2014/8/15
N2 - Fluoroquinolone (FQ) antibacterials are aquatic contaminants of emerging concern (CEC), and adsorption to mineral surfaces is expected to play an important role in the fate, transport, and treatment of FQs. This study characterizes and models the adsorption of a zwitterionic FQ, ofloxacin (OFX), to goethite (α-FeOOH) over a wide range of pH (3-11), OFX concentration (20-500μM), and electrolyte compositions (0.001-0.1M NaCl and NaClO4). Comparing OFX adsorption to structural analogues demonstrates that the carboxylate group is essential for binding to goethite. ATR-FTIR measurements indicate that FQs complex to goethite surfaces through carboxylate and carbonyl oxygen atoms, and that ClO4- co-adsorbs with OFX. Adsorption of the zwitterionic OFX increases with increasing ionic strength and is enhanced in NaClO4 relative to NaCl electrolyte, whereas adsorption of a non-zwitterionic analogue is insensitive to ionic strength. A CD-MUSIC (charge distribution-multisite complexation) model, incorporating multiple modes of surface complexation constrained by spectroscopic measurements and the crystallographic distribution of goethite surface sites, yields accurate predictions over wide-ranging solution conditions. According to the model, OFX adsorbs predominantly by inner-sphere complexation on terminal surfaces of the rod-shaped goethite crystals in NaCl electrolyte, and OFX-ClO4- ion pairing in NaClO4 induces formation of additional inner- and outer-sphere surface complexes on multiple crystal faces of goethite.
AB - Fluoroquinolone (FQ) antibacterials are aquatic contaminants of emerging concern (CEC), and adsorption to mineral surfaces is expected to play an important role in the fate, transport, and treatment of FQs. This study characterizes and models the adsorption of a zwitterionic FQ, ofloxacin (OFX), to goethite (α-FeOOH) over a wide range of pH (3-11), OFX concentration (20-500μM), and electrolyte compositions (0.001-0.1M NaCl and NaClO4). Comparing OFX adsorption to structural analogues demonstrates that the carboxylate group is essential for binding to goethite. ATR-FTIR measurements indicate that FQs complex to goethite surfaces through carboxylate and carbonyl oxygen atoms, and that ClO4- co-adsorbs with OFX. Adsorption of the zwitterionic OFX increases with increasing ionic strength and is enhanced in NaClO4 relative to NaCl electrolyte, whereas adsorption of a non-zwitterionic analogue is insensitive to ionic strength. A CD-MUSIC (charge distribution-multisite complexation) model, incorporating multiple modes of surface complexation constrained by spectroscopic measurements and the crystallographic distribution of goethite surface sites, yields accurate predictions over wide-ranging solution conditions. According to the model, OFX adsorbs predominantly by inner-sphere complexation on terminal surfaces of the rod-shaped goethite crystals in NaCl electrolyte, and OFX-ClO4- ion pairing in NaClO4 induces formation of additional inner- and outer-sphere surface complexes on multiple crystal faces of goethite.
KW - CD-MUSIC
KW - Emerging contaminants
KW - Fluoroquinolone
KW - Ion pair
KW - Iron oxide
KW - Surface complexation
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U2 - 10.1016/j.jcis.2014.04.034
DO - 10.1016/j.jcis.2014.04.034
M3 - Article
C2 - 24910036
AN - SCOPUS:84899895690
SN - 0021-9797
VL - 428
SP - 63
EP - 72
JO - Journal of Colloid And Interface Science
JF - Journal of Colloid And Interface Science
ER -