Mechanism, Kinetics, and Potential of Mean Force of Evaporation of Water from Aqueous Sodium Chloride Solutions of Varying Concentrations

Abstract

The mechanism, kinetics, and potential of mean force of evaporation of water from aqueous NaCl solutions are investigated through both unbiased molecular dynamics simulations and also biased simulations using the umbrella sampling method. The results are obtained for aqueous solutions of three different NaCl concentrations ranging from 0.6 to 6.0 m and also for pure water. The rate of evaporation is found to decrease in the presence of ions. It is found that the process of evaporation of a surface water molecule from ionic solutions can be triggered through its collision with another water or chloride ion. Such collisions provide the additional kinetic energy that is required for evaporation. However, when the collision takes place with a Cl − ion, the evaporation of the escaping water also involves a collision with water in the vicinity of the ion at the same time along with the ion−water collision. These two collisions together provide the required kinetic energy for escape of the evaporating water molecule. Thus, the mechanism of evaporation process of ionic solutions can be more complex than that of pure water. The potential of mean force (PMF) of evaporation is found to be positive and it increases with increasing ion concentration. Also, no barrier in the PMF is found to be present for the condensation of water from vapor phase to the surfaces of the solutions. A detailed analysis of the unsuccessful evaporation attempts by surface water molecules is also made in the current study.

Development of an UV−Resistant Multilayer Film with Enhanced Compatibility between Carboxymethyl Cellulose and Polylactic Acid via Incorporation of Tannin and Ferric Chloride

“…This suggests that, in the absence of TA, a substantial portion of FeCl 3 integrates into the droplets formed during self−assembly, barring a minor fraction that quickly binds with CMC. These FeCl 3 −rich droplets fail to disperse evenly across the CMC surface or evaporate swiftly, leading to their prolonged presence on the CMC layer’s surface and the eventual emergence of defects [ 54 ]. This phenomenon may account for the lower elongation at break observed in the CMC−PLA/Fe film compared to the CMC/TA−PLA/Fe film without a corresponding increase in tensile strength.…”

Variability of entropy force and its coupling with electrostatic and steric hindrance interactions

“…Figure 11 illustrates the impact of the electrostatic correlation on the EIP by examining the difference between considering and disregarding the correlation effect between the hard sphere repulsion and electrostatic interactions, which can simply be done by retaining or removing the F coup [{ρ i }] term from equation (2). We can observe that the correlation effect exerts a qualitative impact on EIP: it is precisely the correlation effect that results in the emergence of LCA in 1:1 electrolyte solutions.…”

“…The potential of mean force, or effective interaction potential (EIP), between particles (where the term 'particle' encompasses molecules, colloidal particles, and clusters) plays a crucial role in various contexts, such as collision rates [1,2], dispersion stability [3][4][5], ion-ligand association [6,7], particle assembly [8], enrichment and fractionation during hydrothermal transport process [9,10]. Although the EIP acquires distinct names in different situations, the underlying phenomena share common features.…”

Laterally Heterogeneous Structure and Dynamics of Water and Ion inside a Nanochannel of a Covalent Organic Framework Membrane Designed for Osmotic Energy Conversion

“…Recent suggestions propose compensating for the lack of polarization in nonpolarizable models of aqueous electrolytes by scaling ion charges with a factor of 1/√ε el , where ε el represents the electronic part of the static relative permittivity of water (ε el = 1.78 for water). − This approach effectively accounts for electronic polarization effects within an electronic continuum correction (ECC). Following this, we fix the charge of SO 3 – group and K + ion as −0.75 and +0.75, respectively, using the steps shown in Table .…”