电场条件下高盐溶液蒸发的分子动力学模拟

Evaporation of High-salt Solution Under Electric Field

摘要:

已有研究表明，外加电场能显著改变纯水蒸发过程和蒸发速率。为了探究外加电场对高盐溶液微观结构和蒸发性质的影响，采用分子动力学模拟方法对纯水和LiCl、KCl和CaCl₂3种盐溶液在平行液面（x方向）和垂直液面方向（z方向）上布置外加电场来观察其蒸发过程。模拟计算分析了电场对蒸发速率、水分子取向、氢键以及水合离子的影响，并且观察比较了电场下不同离子在溶液中的运动。结果显示，与纯水相反，平行液面的电场能显著提高盐溶液中自由水分子的占比，当平行液面电场强度从0变为0.3 v·nm^-1时，LiCl、KCl和CaCl₂溶液中用于评价蒸发的自由水分子占比分别增加了48%，38%和56%，高盐溶液蒸发速率得到有效提高。

Abstract:

Recent studies show that an applied electric field can significantly alter the evaporation process and evaporation rate of pure water. In order to investigate the effect of the applied electric field on the microstructure and evaporation properties of high salt solutions， molecular dynamics simulations （MD） were adopted to simulate pure water and LiCl， KCl and CaCl₂ salt solutions in parallel （x-direction） and perpendicular （z-direction） directions to the liquid. Based on the simulation results， the influence of the electric field on the evaporation speed， the orientation of water molecules， hydrogen bonding and hydrated ions was analyzed， and the motion of different ions in the solution under the electric field was detected and compared. The electric field in the x-direction can significantly increase the proportion of free water molecules in the salt solution. When the electric field in the x-direction modulates from 0 to 0.3 v·nm^-1， the proportion of free water molecules in LiCl， KCl and CaCl₂ solutions augment by 48%， 38% and 56% respectively， effectively enhancing the evaporation rate of the high-salt solution.