Dynamic water absorption-desorption by aqueous salt solutions

Salt solutions have attracted significant interest as water sorbents for a wide range of applications due to their large hygroscopicity and low cost. However, despite their promise, no existing model fully describes the experimentally observed absorption and desorption behavior of salts. Here, we develop a model that accurately captures absorption and desorption of water vapor into salt solutions. Our results show that the nonlinear driving force due to the chemical activity of water leads to previously unexplained behaviors such as faster desorption than absorption and absorption-rate dependence on humidity. We leverage our model to demonstrate the trade-off of uptake and sorption time as the humidity and salt type are changed and show the dependence of the timescale on the system's parameters. This model represents a fundamental advancement in the understanding of salt solution absorption-desorption and supports the optimization of water sorption applications.