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Title (Primary) Measuring and modeling the salting-out effect in ammonium sulfate solutions
Author Wang, C.; Lei, Y.D.; Endo, S.; Wania, F.
Journal Environmental Science & Technology
Year 2014
Department AUC
Volume 48
Issue 22
Page From 13238
Page To 13245
Language englisch
UFZ wide themes RU3;
Abstract The presence of inorganic salts significantly influences the partitioning behavior of organic compounds between environmentally relevant aqueous phases, such as sea water or aqueous aerosol, and other, non-aqueous phases (gas phase, organic phase, etc.). In this study, salting-out coefficients (or Setschenow constants) (KS [M-1]) for 38 diverse neutral compounds in ammonium sulfate ((NH4)2SO4) solutions were measured using a shared headspace passive dosing method and a negligible depletion solid phase microextraction technique. The measured K¬S were all positive, varied from 0.216 to 0.729, and had standard errors in the range of 0.006-0.060. Compared to KS for sodium chloride (NaCl) in the literature, KS values for (NH4)2SO4 are always higher for the same compound, suggesting a higher salting-out effect of (NH4)2SO4. A polyparameter linear free energy relationship (pp-LFER) for predicting KS in (NH4)2SO4 solutions was generated using the experimental data for calibration. pp-LFER predicted KS agreed well with measured KS reported in the literature. KS for (NH4)2SO4 was also predicted using the quantum-chemical COSMOtherm software and the thermodynamic model AIOMFAC. While COSMOtherm generally overpredicted the experimental KS, predicted and experimental values were correlated. Therefore, a fitting factor needs to be applied when using the current version of COSMOtherm to predict KS. AIOMFAC tends to underpredict the measured KS((NH4)2SO4), but always overpredicts KS(NaCl). The prediction error is generally larger for KS(NaCl) than for KS((NH4)2SO4). AIOMFAC also predicted a dependence of KS on the salt concentrations, which is not observed in the experimental data. In order to demonstrate that the models developed and calibrated in this study can be applied to estimate Setschenow coefficients for atmospherically relevant compounds involved in secondary organic aerosol formation based on chemical structure alone, we predicted and compared KS for selected α-pinene oxidation products.
Persistent UFZ Identifier
Wang, C., Lei, Y.D., Endo, S., Wania, F. (2014):
Measuring and modeling the salting-out effect in ammonium sulfate solutions
Environ. Sci. Technol. 48 (22), 13238 - 13245