Acid-Base Speciation of Carboxylate Ions in the Surface Region of Aqueous Solutions in the Presence of Ammonium and Aminium Ions
Author
Summary, in English
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.
Department/s
Publishing year
2015
Language
English
Pages
4033-4040
Publication/Series
The Journal of Physical Chemistry Part B
Volume
119
Issue
10
Document type
Journal article
Publisher
The American Chemical Society (ACS)
Topic
- Natural Sciences
- Physical Sciences
Status
Published
ISBN/ISSN/Other
- ISSN: 1520-5207