Molecular Dynamics Simulations on Evaporation of Droplets with Dissolved Salts

Molecular dynamics simulations are used to study the evaporation of water droplets containing either dissolved LiCl, NaCl or KCl salt in a gaseous surrounding (nitrogen) with a constant high temperature of 600 K. The initial droplet has 298 K temperature and contains 1,120 water molecules, 0, 40, 80 or 120 salt molecules. The effects of the salt type and concentration on the evaporation rate are examined. Three stages with different evaporation rates are observed for all cases. In the initial stage of evaporation, the droplet evaporates slowly due to low droplet temperature and high evaporation latent heat for water, and pure water and aqueous solution have almost the same evaporation rates. In the second stage, evaporation rate is increased significantly, and evaporation is somewhat slower for the aqueous salt-containing droplet than the pure water droplet due to the attracted ion-water interaction and hydration effect. The Li+-water has the strongest interaction and hydration effect, so LiCl aqueous droplets evaporate the slowest, then NaCl and KCl. Higher salt concentration also enhances the ion-water interaction and hydration effect, and hence corresponds to a slower evaporation. In the last stage of evaporation, only a small amount of water molecules are left in the droplet, leading to a significant increase in ion-water interactions, so that the evaporation becomes slower compared to that in the second stage.

[1]  Siswo Sumardiono,et al.  Molecular simulations of droplet evaporation by heat transfer , 2007 .

[2]  N. M. Cann,et al.  Molecular dynamics simulations to examine structure, energetics, and evaporation/condensation dynamics in small charged clusters of water or methanol containing a single monatomic ion. , 2012, The journal of physical chemistry. A.

[3]  H. Köhler.  The nucleus in and the growth of hygroscopic droplets , 1936 .

[4]  B. C. Garrett,et al.  Ions at the Air/Water Interface , 2004, Science.

[5]  Eyal Zussman,et al.  Experimental investigation of the governing parameters in the electrospinning of polymer solutions , 2004 .

[6]  Douglas J. Tobias,et al.  Molecular Structure of Salt Solutions: A New View of the Interface with Implications for Heterogeneous Atmospheric Chemistry , 2001 .

[7]  N. V. Churaev,et al.  Crystal growth at the end of a capillary on solution evaporation , 1988 .

[8]  Hao Wang,et al.  A molecular dynamics investigation on evaporation of thin liquid films , 2012 .

[9]  Akos Vertes,et al.  Solvated Ion Evaporation from Charged Water Nanodroplets , 2003 .

[10]  Carl Caleman,et al.  Evaporation from water clusters containing singly charged ions. , 2007, Physical chemistry chemical physics : PCCP.

[11]  Xin Li,et al.  Surface-Active cis-Pinonic Acid in Atmospheric Droplets: A Molecular Dynamics Study , 2010 .

[12]  Phillip E Mason,et al.  Molecular dynamics study on the microscopic details of the evaporation of water. , 2011, The journal of physical chemistry. A.

[13]  S. W. Leeuw,et al.  An Iterative PPPM Method for Simulating Coulombic Systems on Distributed Memory Parallel Computers , 1998 .

[14]  Manuel G. Velarde,et al.  Droplets evaporation: Problems and solutions , 2011 .

[15]  Chun Yang,et al.  Molecular dynamics study on the liquid–vapor interfacial profiles , 2001 .

[16]  N. M. Cann,et al.  How are completely desolvated ions produced in electrospray ionization: insights from molecular dynamics simulations. , 2011, Analytical chemistry.

[17]  Shigeo Maruyama,et al.  Surface Phenomena of Molecular Clusters by Molecular Dynamics Method , 1996 .

[18]  Sergey Semenov,et al.  Computer simulations of evaporation of pinned sessile droplets: influence of kinetic effects. , 2012, Langmuir : the ACS journal of surfaces and colloids.

[19]  Lyle N. Long,et al.  Supercritical vaporization of liquid oxygen droplets using molecular dynamics , 1998 .

[20]  Yoshio Sone,et al.  Kinetic Theory Analysis of Steady Evaporating Flows from a Spherical Condensed Phase into a Vacuum , 1993 .

[21]  Sohail Murad,et al.  A molecular dynamics simulation of droplet evaporation , 2003 .

[22]  Yaoquan Tu,et al.  Molecular dynamics simulations of the surface tension and structure of salt solutions and clusters. , 2012, The journal of physical chemistry. B.

[23]  Salah Nasr,et al.  Local order in aqueous lithium chloride solutions as studied by X-ray scattering and molecular dynamics simulations , 2007 .

[24]  Martin Mucha,et al.  Salt Crystallization from an Evaporating Aqueous Solution by Molecular Dynamics Simulations , 2003 .

[25]  Petros Koumoutsakos,et al.  Molecular Dynamics Simulation of Nanodroplet Evaporation , 2001 .

[26]  Lyle N. Long,et al.  Molecular dynamics simulations of droplet evaporation , 1994 .

[27]  Amalendu Chandra,et al.  Molecular dynamics simulations of aqueous NaCl and KCl solutions: Effects of ion concentration on the single-particle, pair, and collective dynamical properties of ions and water molecules , 2001 .

[28]  V. Carey,et al.  Disjoining Pressure Effects in Ultra-Thin Liquid Films in Micropassages—Comparison of Thermodynamic Theory With Predictions of Molecular Dynamics Simulations , 2006 .

[29]  Shigeo Maruyama,et al.  Molecular dynamics simulation of an evaporating sodium droplet , 1999 .

[30]  Alan J. H. McGaughey,et al.  Droplet evaporation: A molecular dynamics investigation , 2007 .

[31]  Manuel G. Velarde,et al.  Evaporation of sessile water droplets: Universal behaviour in presence of contact angle hysteresis , 2011 .

[32]  Gerard M. Faeth,et al.  CURRENT STATUS OF DROPLET AND LIQUID COMBUSTION , 1977 .

[33]  P. Cremer,et al.  Interactions between macromolecules and ions: The Hofmeister series. , 2006, Current opinion in chemical biology.