The effect of fatty acid surfactants on the uptake of ozone to aqueous halogenide particles

The reactive uptake of ozone to deliquesced potassium iodide aerosol particles coated with linear saturated fatty acids (C sub(9), C sub(12), C sub(15), C sub(18) and C sub(20)) as surfactants was studied. The experiments were performed in an aerosol flow tube at 293 K and atmospheric pressure. The uptake coefficient on pure deliquesced KI aerosol was g=(1.10c0.20)10 super(− 2) at 72-75% relative humidity. In presence of organic coatings, the uptake coefficient decreased significantly for long straight chain surfactants (>C sub(15)), while it was only slightly reduced for the short ones (C sub(9), C sub(12)). We linked the kinetic results to the monolayer properties of the surfactants, and specifically to the phase state of the monolayer formed (liquid expanded or liquid condensed state). We also investigated the effect of organic films to mixed deliquesced aerosol composed of a variable mixture of KI and NaCl, which allowed determining the resistance exerted to O sub(3) at the aqueous surface by the two longer chained surfactants pentadecanoic acid (C sub(15)) and stearic acid (C sub(18)). Finally, the effect of two-component coatings, consisting of a mixture of long and short chained surfactants, was also studied.