Effects of organics on efflorescence relative humidity of ammonium sulfate or sodium chloride particles

The effect of a water-soluble organics on efflorescence relative humidity (ERH) of ammonium sulfate or sodium chloride particles is theoretically investigated on the basis of a previously developed model for ERH of single-component particles [Gao et al., 2006. Efflorescence relative humidity for ammonium sulfate particles Journal of Physical Chemistry A 110, 7602–7608]. The central assumption made is that one species nucleates much faster than the other, and the critical nuclei formation of the former controls the rate of efflorescence. The water-soluble organics (WSOs) appeared to suppress the ERH of salt particles; the decrease in ERH can be more than 30% RH when the mole fraction of WSO is larger than 0.5. The developed model satisfactorily makes quantitative prediction only for the ERH of mixed particles containing WSO with low-surface active nature (glycerol, levoglucosan, and malonic acid). For mixed particles having more surface-active WSO (glutaric and maleic acid), the inaccurate prediction is attributable to the negligence of interactions between solutes and the estimation of interfacial tension between nuclei and the mixed solution.