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Inner-sphere and outer-sphere complexation of a polycarboxylic acid at the water-boehmite (gamma-AlOOH) interface: A combined potentiometric and IR spectroscopic study

Nordin, J.; Persson, Per LU ; Nordin, A. and Sjoberg, S. (1998) In Langmuir 14. p.3655-3662
Abstract
Speciation and equilibria of 1,2,4,5-benzenetetracarboxylate (pyromellitate) at the water-boehmite (gamma-AlOOH) interface were studied in 0.1 M Na(Cl) at 298 K. Surface equilibrium analyses were based upon potentiometric and adsorption measurements in the range 4.5 < pH < 10.0. To characterize the surface complexes at the molecular level, attenuated total reflectance infrared spectra were recorded. The IR data provided information on the structure and composition of the complexes. This information could then be used to constrain the thermodynamic surface complexation model. The acid/base properties of pyromellitate in solution and its complexation with. Al(III) mere also studied by means of potentiometric titrations in 0.1 M Na(Cl)... (More)
Speciation and equilibria of 1,2,4,5-benzenetetracarboxylate (pyromellitate) at the water-boehmite (gamma-AlOOH) interface were studied in 0.1 M Na(Cl) at 298 K. Surface equilibrium analyses were based upon potentiometric and adsorption measurements in the range 4.5 < pH < 10.0. To characterize the surface complexes at the molecular level, attenuated total reflectance infrared spectra were recorded. The IR data provided information on the structure and composition of the complexes. This information could then be used to constrain the thermodynamic surface complexation model. The acid/base properties of pyromellitate in solution and its complexation with. Al(III) mere also studied by means of potentiometric titrations in 0.1 M Na(Cl) at 298 K. The results of these measurements were primarily used to investigate the effect of pyromellitate on the dissolution of boehmite. In aqueous solution Al(III) forms a series of mononuclear complexes, namely, AlHL, AlL-, and Al(OH)L2-. No indication of polynuclear complexes was found within the concentration ranges studied. IR spectra of pyromellitate sorbed at the water-boehmite interface suggested the existence of one dominating surface complex over a wide pH range (4.4 less than or equal to pH less than or equal to 8.1). The IR spectroscopic characteristics of this complex were in agreement with an enter-sphere nonprotonated pyromellitate ion. No evidence was found fur protonation of the sorbed ion. Thus, the nonprotonated form is greatly stabilized at the interface as compared to the speciation in the aqueous solution. The IR data also showed some indications of a second minor surface complex. This was tentatively assigned to an inner-sphere species. According to the constraints provided by the IR data, the potentiometric and adsorption data were modeled with two surface complexes, =AlOH2+L4- (outer-sphere) and =AlL- (inner-sphere). The extended constant capacitance mod.el was used to account for the electrostatic effects at the interface. The agreement between the experimental data and the model was satisfactory. Furthermore, the model was also in agreement with the minor changes observed in the IR spectra as a function of pH. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
in
Langmuir
volume
14
pages
3655 - 3662
publisher
The American Chemical Society
external identifiers
  • scopus:0032098666
ISSN
0743-7463
DOI
10.1021/la9712449
language
English
LU publication?
no
id
0a7946a9-2211-43e5-b637-0776b02b9538 (old id 4332646)
date added to LUP
2014-03-04 09:42:27
date last changed
2017-06-04 03:47:30
@article{0a7946a9-2211-43e5-b637-0776b02b9538,
  abstract     = {Speciation and equilibria of 1,2,4,5-benzenetetracarboxylate (pyromellitate) at the water-boehmite (gamma-AlOOH) interface were studied in 0.1 M Na(Cl) at 298 K. Surface equilibrium analyses were based upon potentiometric and adsorption measurements in the range 4.5 &lt; pH &lt; 10.0. To characterize the surface complexes at the molecular level, attenuated total reflectance infrared spectra were recorded. The IR data provided information on the structure and composition of the complexes. This information could then be used to constrain the thermodynamic surface complexation model. The acid/base properties of pyromellitate in solution and its complexation with. Al(III) mere also studied by means of potentiometric titrations in 0.1 M Na(Cl) at 298 K. The results of these measurements were primarily used to investigate the effect of pyromellitate on the dissolution of boehmite. In aqueous solution Al(III) forms a series of mononuclear complexes, namely, AlHL, AlL-, and Al(OH)L2-. No indication of polynuclear complexes was found within the concentration ranges studied. IR spectra of pyromellitate sorbed at the water-boehmite interface suggested the existence of one dominating surface complex over a wide pH range (4.4 less than or equal to pH less than or equal to 8.1). The IR spectroscopic characteristics of this complex were in agreement with an enter-sphere nonprotonated pyromellitate ion. No evidence was found fur protonation of the sorbed ion. Thus, the nonprotonated form is greatly stabilized at the interface as compared to the speciation in the aqueous solution. The IR data also showed some indications of a second minor surface complex. This was tentatively assigned to an inner-sphere species. According to the constraints provided by the IR data, the potentiometric and adsorption data were modeled with two surface complexes, =AlOH2+L4- (outer-sphere) and =AlL- (inner-sphere). The extended constant capacitance mod.el was used to account for the electrostatic effects at the interface. The agreement between the experimental data and the model was satisfactory. Furthermore, the model was also in agreement with the minor changes observed in the IR spectra as a function of pH.},
  author       = {Nordin, J. and Persson, Per and Nordin, A. and Sjoberg, S.},
  issn         = {0743-7463},
  language     = {eng},
  pages        = {3655--3662},
  publisher    = {The American Chemical Society},
  series       = {Langmuir},
  title        = {Inner-sphere and outer-sphere complexation of a polycarboxylic acid at the water-boehmite (gamma-AlOOH) interface: A combined potentiometric and IR spectroscopic study},
  url          = {http://dx.doi.org/10.1021/la9712449},
  volume       = {14},
  year         = {1998},
}