Your browser has javascript turned off or blocked. This will lead to some parts of our website to not work properly or at all. Turn on javascript for best performance.

The browser you are using is not supported by this website. All versions of Internet Explorer are no longer supported, either by us or Microsoft (read more here: https://www.microsoft.com/en-us/microsoft-365/windows/end-of-ie-support).

Please use a modern browser to fully experience our website, such as the newest versions of Edge, Chrome, Firefox or Safari etc.

Per Persson. Photo.

Per Persson

Director

Per Persson. Photo.

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

Author

  • J. Nordin
  • Per Persson
  • A. Nordin
  • S. Sjoberg

Summary, in English

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.

Publishing year

1998

Language

English

Pages

3655-3662

Publication/Series

Langmuir

Volume

14

Document type

Journal article

Publisher

The American Chemical Society (ACS)

Topic

  • Earth and Related Environmental Sciences

Status

Published

ISBN/ISSN/Other

  • ISSN: 0743-7463