TY - JOUR
T1 - Surface complexes of phthalic acid at the hematite/water interface
AU - Hwang, Yu Sik
AU - Liu, Jin
AU - Lenhart, John J.
AU - Hadad, Christopher M.
N1 - Funding Information:
We wish to acknowledge the NSF-funded Environmental Molecular Science Institute (CHE-0089147) at Ohio State University for financial support of this research. Also, the Ohio Supercomputer Center provided a generous grant of computational resources.
Copyright:
Copyright 2008 Elsevier B.V., All rights reserved.
PY - 2007/3/1
Y1 - 2007/3/1
N2 - The adsorption of o-phthalic acid at the hematite/water interface was investigated experimentally using batch adsorption experiments and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy over a wide range of solution pH, surface loading, and ionic strength conditions. Molecular orbital calculations for several possible surface complexes were also performed to assign atomistic structures to the features observed in the ATR-FTIR spectra. The results of the batch adsorption experiments exhibit typical anionic characteristics with high adsorption at low pH and low adsorption at high pH. The adsorption of phthalic acid also exhibits a strong dependence on ionic strength, which suggests the presence of outer-sphere complexes. ATR-FTIR spectra provide evidence of three fully deprotonated phthalate surface complexes (an outer-sphere complex and two inner-sphere complexes) under variable chemical conditions. A fully deprotonated outer-sphere complex appears to dominate adsorption in the circumneutral pH region, while two fully deprotonated inner-sphere complexes that shift in relative importance with surface coverage increase in importance at low pH. Comparison of experimental and theoretical calculations suggests the two inner-sphere complexes are best described as a mononuclear bidentate (chelating) complex and a binuclear bidentate (bridging) complex. The mononuclear bidentate inner-sphere complex was favored at relatively low surface coverage. With increasing surface coverage, the relative contribution of the binuclear bidentate inner-sphere complex increased in importance.
AB - The adsorption of o-phthalic acid at the hematite/water interface was investigated experimentally using batch adsorption experiments and attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy over a wide range of solution pH, surface loading, and ionic strength conditions. Molecular orbital calculations for several possible surface complexes were also performed to assign atomistic structures to the features observed in the ATR-FTIR spectra. The results of the batch adsorption experiments exhibit typical anionic characteristics with high adsorption at low pH and low adsorption at high pH. The adsorption of phthalic acid also exhibits a strong dependence on ionic strength, which suggests the presence of outer-sphere complexes. ATR-FTIR spectra provide evidence of three fully deprotonated phthalate surface complexes (an outer-sphere complex and two inner-sphere complexes) under variable chemical conditions. A fully deprotonated outer-sphere complex appears to dominate adsorption in the circumneutral pH region, while two fully deprotonated inner-sphere complexes that shift in relative importance with surface coverage increase in importance at low pH. Comparison of experimental and theoretical calculations suggests the two inner-sphere complexes are best described as a mononuclear bidentate (chelating) complex and a binuclear bidentate (bridging) complex. The mononuclear bidentate inner-sphere complex was favored at relatively low surface coverage. With increasing surface coverage, the relative contribution of the binuclear bidentate inner-sphere complex increased in importance.
KW - ATR-FTIR spectroscopy
KW - Adsorption
KW - Hematite
KW - Inner-sphere complex
KW - Molecular orbital calculations
KW - Outer-sphere complex
KW - Phthalic acid
UR - http://www.scopus.com/inward/record.url?scp=33847062499&partnerID=8YFLogxK
U2 - 10.1016/j.jcis.2006.11.020
DO - 10.1016/j.jcis.2006.11.020
M3 - Article
C2 - 17188289
AN - SCOPUS:33847062499
SN - 0021-9797
VL - 307
SP - 124
EP - 134
JO - Journal of Colloid and Interface Science
JF - Journal of Colloid and Interface Science
IS - 1
ER -