TY - JOUR
T1 - PH Dependence of Liquid-Liquid Phase Separation in Organic Aerosol
AU - Losey, Delanie J.
AU - Parker, Robert G.
AU - Freedman, Miriam Arak
N1 - Publisher Copyright:
© 2016 American Chemical Society.
PY - 2016/10/6
Y1 - 2016/10/6
N2 - Atmospheric aerosol particles influence climate through their direct and indirect effects. These impacts depend in part on the morphology of the particles, which is determined by their composition. The effect of pH on morphology was investigated using particles composed of 3-methylglutaric acid and ammonium sulfate by manipulating the starting pH of the bulk solution through the addition of aqueous sodium hydroxide. Efflorescence, deliquescence, phase separation, and mixing transitions were observed with optical microscopy. Due to changes in its protonation states, the solubility of the organic component increases with increasing pH, which shifts the location of the separation relative humidity (SRH) from 78.7% for the fully protonated acid to 63.9% for the fully deprotonated acid. Surprisingly, this shift in the SRH leads to hysteresis between the SRH and the mixing relative humidity (MRH). Particle pH has the greatest effect on phase transitions that require nucleus formation, that is, efflorescence and SRH.
AB - Atmospheric aerosol particles influence climate through their direct and indirect effects. These impacts depend in part on the morphology of the particles, which is determined by their composition. The effect of pH on morphology was investigated using particles composed of 3-methylglutaric acid and ammonium sulfate by manipulating the starting pH of the bulk solution through the addition of aqueous sodium hydroxide. Efflorescence, deliquescence, phase separation, and mixing transitions were observed with optical microscopy. Due to changes in its protonation states, the solubility of the organic component increases with increasing pH, which shifts the location of the separation relative humidity (SRH) from 78.7% for the fully protonated acid to 63.9% for the fully deprotonated acid. Surprisingly, this shift in the SRH leads to hysteresis between the SRH and the mixing relative humidity (MRH). Particle pH has the greatest effect on phase transitions that require nucleus formation, that is, efflorescence and SRH.
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U2 - 10.1021/acs.jpclett.6b01621
DO - 10.1021/acs.jpclett.6b01621
M3 - Article
C2 - 27636827
AN - SCOPUS:84990061992
SN - 1948-7185
VL - 7
SP - 3861
EP - 3865
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 19
ER -
