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Acid-Base Speciation of Carboxylate Ions in the Surface Region of Aqueous Solutions in the Presence of Ammonium and Aminium Ions

Öhrwall, Gunnar LU ; Prisle, Nonne L.; Ottosson, Niklas; Werner, Josephina; Ekholm, Victor; Walz, Marie-Madeleine and Bjorneholm, Olle (2015) In The Journal of Physical Chemistry Part B 119(10). p.4033-4040
Abstract
The acid base speciation of surface-active carboxylate ions in the surface region of aqueous solutions was studied with synchrotron-radiation-based photoelectron spectroscopy. The protonated form was found at an extraordinarily large fraction compared to that expected from the bulk pH. When adding salts containing the weak acid NH4+ to the solution, the fraction of the acidic form at the surface increases, and to a Much greatet extent than expected from the bulk pH of the solution. We show that ammonium ions also are overrepresented in the surface region, and propose that the interaction between the surface-active anionic carboxylates and cationic ammonium ions creates a carboxylateammonium bilayer close to the surface, which increases the... (More)
The acid base speciation of surface-active carboxylate ions in the surface region of aqueous solutions was studied with synchrotron-radiation-based photoelectron spectroscopy. The protonated form was found at an extraordinarily large fraction compared to that expected from the bulk pH. When adding salts containing the weak acid NH4+ to the solution, the fraction of the acidic form at the surface increases, and to a Much greatet extent than expected from the bulk pH of the solution. We show that ammonium ions also are overrepresented in the surface region, and propose that the interaction between the surface-active anionic carboxylates and cationic ammonium ions creates a carboxylateammonium bilayer close to the surface, which increases the probability of the protonation of the carboxylae ions. By comparing the situation when a salt of the less volatile amine diethanolatnine is used, We also show that the observed evaporation of ammonia that occurs after such an event only affects the equilibrium marginally. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
The Journal of Physical Chemistry Part B
volume
119
issue
10
pages
4033 - 4040
publisher
The American Chemical Society
external identifiers
  • wos:000351188300016
  • scopus:84924560323
ISSN
1520-5207
DOI
10.1021/jp509945g
language
English
LU publication?
yes
id
e26a6f4e-cb7c-4c0a-801a-e82cad23b269 (old id 5287883)
date added to LUP
2015-04-24 13:55:06
date last changed
2017-06-25 04:01:46
@article{e26a6f4e-cb7c-4c0a-801a-e82cad23b269,
  abstract     = {The acid base speciation of surface-active carboxylate ions in the surface region of aqueous solutions was studied with synchrotron-radiation-based photoelectron spectroscopy. The protonated form was found at an extraordinarily large fraction compared to that expected from the bulk pH. When adding salts containing the weak acid NH4+ to the solution, the fraction of the acidic form at the surface increases, and to a Much greatet extent than expected from the bulk pH of the solution. We show that ammonium ions also are overrepresented in the surface region, and propose that the interaction between the surface-active anionic carboxylates and cationic ammonium ions creates a carboxylateammonium bilayer close to the surface, which increases the probability of the protonation of the carboxylae ions. By comparing the situation when a salt of the less volatile amine diethanolatnine is used, We also show that the observed evaporation of ammonia that occurs after such an event only affects the equilibrium marginally.},
  author       = {Öhrwall, Gunnar and Prisle, Nonne L. and Ottosson, Niklas and Werner, Josephina and Ekholm, Victor and Walz, Marie-Madeleine and Bjorneholm, Olle},
  issn         = {1520-5207},
  language     = {eng},
  number       = {10},
  pages        = {4033--4040},
  publisher    = {The American Chemical Society},
  series       = {The Journal of Physical Chemistry Part B},
  title        = {Acid-Base Speciation of Carboxylate Ions in the Surface Region of Aqueous Solutions in the Presence of Ammonium and Aminium Ions},
  url          = {http://dx.doi.org/10.1021/jp509945g},
  volume       = {119},
  year         = {2015},
}