Benzenecarboxylate surface complexation at the goethite (alpha-FeOOH)/water interface: I. A mechanistic description of pyromellitate surface complexes from the combined evidence of infrared spectroscopy, potentiometry, adsorption data, and surface complexation modeling

Citation
Jf. Boily et al., Benzenecarboxylate surface complexation at the goethite (alpha-FeOOH)/water interface: I. A mechanistic description of pyromellitate surface complexes from the combined evidence of infrared spectroscopy, potentiometry, adsorption data, and surface complexation modeling, LANGMUIR, 16(13), 2000, pp. 5719-5729
Citations number
36
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
LANGMUIR
ISSN journal
07437463 → ACNP
Volume
16
Issue
13
Year of publication
2000
Pages
5719 - 5729
Database
ISI
SICI code
0743-7463(20000627)16:13<5719:BSCATG>2.0.ZU;2-6
Abstract
An investigation combining IR spectroscopy, potentiometric titrations, and adsorption experiments was carried out to study pyromellitate (1,2,4,5-benz enetetracarboxylate) sorption at the goethite (alpha-FeOOH)/ water interfac e. The IR spectra show evidence of outer-sphere complexation throughout the pH range from 3 to 9. Below pH 6 additional IR spectroscopic features appe ar, which are tentatively assigned to inner-sphere complexes. A normalized IR peak area plot for each peak indicative of inner- and of outer-sphere co mplexes as a function of pH provided a semiquantitative surface speciation scheme. This scheme was successfully reproduced using surface complexation theory with a multisite complexation model calibrated on potentiometric tit ration and on adsorption data. The surface speciation was described with a binuclear outer-sphere complex on the {110} plane of goethite and a mononuc lear inner-sphere complex on the {001} plane. Furthermore, as the IR spectr a also indicated partial protonation of pyromellitate complexes at low pH, a partially protonated outer-sphere species on the {110} plane was included in the model.