Using molecular dynamics simulation, we study the density fluctuation and cavity formation in aqueous solutions and their effects on the hydration of realistic gas like CO2. With increasing salt concentration, we observe an increased probability of observing a larger than the average number of species in the probe volume. In addition, our energetic analysis indicates that interactions of CO2 with aqueous solutions including the van der Waals and electrostatic interactions favor the solubility of CO2 when salt concentration increases (salting in). However, because cavity formation, which was found to be a dominant process in gas dissolution, decreases when increasing salt concentration, it is responsible for a CO2 salting-out effect. Our results provide fundamental understanding of the density fluctuation in aqueous solutions and molecular origin of the salting-out effect for real gas. This work was funded by the Center for Frontiers in Subsurface Energy Security, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001114. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.

Cavity formation in aqueous solutions and molecular origin of salting-out effect for CO2

255th National Meeting (2018)

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