The effect of surfactants on the deliquescence of sodium chloride

This study investigated the deliquescence of sodium chloride aerosol with s urfactants at a retention time of 4.24 sec. Two surfactants used in this st udy, glutaric acid and pyruvic acid, are found in atmospheric aerosol and h ave a high hydrophile-lipophile balance (HLB) value. The experimental syste m consisted of a relative humidity conditioner, a tandem differential mobil ity analyzer (TDMA) and a scanning mobility particle sizing (SMPS) system. Results obtained from the observation of TDMA presented the deliquescence p oint of sodium chloride aerosol at 75%RH. In addition, the growth size of s odium chloride aerosol was observed to be 79.47nm and the growth ratio was 77.94%, when the initial size of aerosol was 101.82nm. Surfactants were int ernally mixed with sodium chloride at six different weight fractions, i.e. 2.5, 5, 10, 20, 40, and 60% by weight of surfactants in dry aerosol. Both s urfactants apparently decreased the deliquescence point of sodium chloride, in which the lowest deliquescence point appeared at about 71%RH when the w eight fraction of surfactants is 60% by weight of surfactants in dry aeroso l. Moreover, the smallest size of sodium chloride aerosol with surfactants was 142.7nm at 60% by weight of pyruvic acid in dry aerosol. Our results fu rther demonstrate that the deliquescence point and size of sodium chloride aerosol with surfactants are related to the weight fraction of surfactants.