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Reactive uptake of N2O5 on aqueous H2SO4 solutions coated with 1-component and 2-component monolayers

TitleReactive uptake of N2O5 on aqueous H2SO4 solutions coated with 1-component and 2-component monolayers
Publication TypeJournal Article
Year of Publication2008
AuthorsCosman, LM, Bertram, AK
JournalJournal of Physical Chemistry A
Volume112
Pagination4625-4635
Date PublishedMay
Type of ArticleArticle
ISBN Number1089-5639
KeywordsAIR-WATER-INTERFACE, ATMOSPHERIC AEROSOL, EVAPORATION RESISTANCES, FILMS, HETEROGENEOUS HYDROLYSIS, MIXED MONOLAYERS, ORGANIC, REACTION PROBABILITIES, SEA-SALT, SULFURIC-ACID PARTICLES, TRANSPORT PROPERTIES
Abstract

Reactive uptake of N2O5 on aqueous sulfuric acid solutions was studied in the presence of 1-component (octadecanol) and 2-component (octadecanol + phytanic acid) monolayers. In the 1-component monolayer experiments, the reactive uptake coefficient depended strongly on the molecular surface area of the surfactant. Also, the 1-component monolayer showed significant resistance to mass transfer even when the fractional surface coverage of the surfactant was less than 1. For example, a monolayer of I-octadecanol with a fractional surface coverage of 0.75 decreased the reactive uptake coefficient by a factor of 10. This is consistent with previous studies. In the 2-component monolayer experiments, the reactive uptake coefficient depended strongly on the composition of the monolayer. When the monolayer contained only straight-chain molecules (1-octadecanol), the reactive uptake coefficient decreased by a factor of 42 due to the presence of the monolayer. However, when the monolayer contained 0.20 mole fraction of a branched surfactant (phytanic acid) the reactive uptake coefficient only decreased by a factor of 2. Hence, a small amount of branched surfactant drastically changes the overall resistance to reactive uptake. Also, our results show that the overall resistance to reactive uptake of 2-component monolayers can be predicted reasonably accurately by a model that assumes the resistances to mass transfer can be combined in parallel.

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