Publication Date:
2012-05-15
Description:
Dilute aqueous solutions of the atmospheric organic surfactant sodium decanoate have been studied using surface sensitive X-ray photoelectron spectroscopy combined with synchrotron radiation. We studied the decanoate/decanoic acid speciation and preferential adsorption at the vapor–liquid interface, and the responses to mixing in solution with some of the most common atmospheric inorganic ions, Na+, NH4+, Cl−, and O42−. We observe no influence of Na+, Cl−, or SO42− ions on neither the relative speciation nor the individual adsorption properties of decanoate and decanoic acid. In particular, the anticipated salting-out effect due to common Na+ cations of the organic and inorganic salts was not observed. On the other hand, mixing with NH4+ cations resulted in a pronounced surface enhancement of decanoic acid, which is attributed to surface specific acid–base chemistry. These changes in surface/bulk partitioning and speciation may significantly affect properties of aqueous droplets containing decanoate/decanoic acid, and potential implications for several processes critical to the climate effects of atmospheric aerosols are discussed.
Electronic ISSN:
1680-7375
Topics:
Geosciences