Wen Boyao, Sun Chengzhen, Bai Bofeng, Gatapova Elizaveta Ya, Kabov Oleg A
State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xian, Shaanxi 710049, China.
Kutateladze Institute of Thermophysics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk 630090, Russia and Novosibirsk State University, Novosibirsk 630090, Russia.
Phys Chem Chem Phys. 2017 Jun 7;19(22):14606-14614. doi: 10.1039/c7cp01826f.
Building a connection between the variations in interfacial tension and the microstructure of the oil-water interface is still very challenging. Here, we employ a molecular dynamics method to study the effect of monovalent ions on the decane-water interfacial tension and reveal the relationship between ionic hydration and the variation of interfacial tension. Our results indicate that interfacial tension presents a non-monotonic dependence on the ionic concentrations owing to the distinctive adsorption characteristics of ions. At low ionic concentrations, the hydration of the discrete ions at the interface causes an enhancement in the virial term of the interfacial tension, resulting in an increase of the interfacial tension with increasing ionic concentrations. At high ionic concentrations, the ion pairs at the interface weaken the ionic hydration, thus the virial term of the interfacial tension decreases and the interfacial tension decreases slightly. In addition, the kinetic energy term of interfacial tension increases only with increasing temperature, while the virial term decreases with an increase in either temperature or pressure on account of the weakening ionic hydration; therefore, the increase of temperature and pressure induces different degrees of the decrease in the interfacial tension owing to the major contribution of the virial term, particularly at high ionic concentrations.
建立界面张力变化与油水界面微观结构之间的联系仍然极具挑战性。在此，我们采用分子动力学方法研究单价离子对癸烷 - 水界面张力的影响，并揭示离子水化与界面张力变化之间的关系。我们的结果表明，由于离子独特的吸附特性，界面张力对离子浓度呈现非单调依赖性。在低离子浓度下，界面处离散离子的水化导致界面张力的维里项增强，从而使界面张力随离子浓度增加而增大。在高离子浓度下，界面处的离子对削弱了离子水化，因此界面张力的维里项减小，界面张力略有下降。此外，界面张力的动能项仅随温度升高而增加，而维里项由于离子水化减弱，随温度或压力升高而减小；因此，由于维里项的主要贡献，温度和压力的升高会导致界面张力不同程度地降低，特别是在高离子浓度下。
