Department of Chemical Engineering, University of Illinois at Chicago, Chicago, Illinios 60607, USA.
J Chem Phys. 2011 Mar 21;134(11):114504. doi: 10.1063/1.3565478.
Molecular simulations have been carried out using the method of molecular dynamics to investigate the role of external electric fields on the ion mobility, drift velocity, and drift-diffusion rate of ions in aqueous electrolyte solutions. These properties are critical for a range of processes including electrodialysis, electro-deionization, electrophoresis, and electroosmosis. Our results show that external electric fields relax the hydrated ion structure at significantly larger time scales (between 300 and 800 ps), than most other relaxation processes in solutions (generally of the order of 1 ps). Previous studies that did not account for the much longer relaxation times did not observe this behavior for ions even with very high electric fields. External electric fields must also overcome several (at least two or more) activation energy barriers to significantly change the structure of hydrated ions. As a result, the dynamic behavior changes almost in bands as a function of electric field strengths, rather than linearly. Finally, the effect of the field is much less dramatic on water than the ions. Thus electric fields will be of more significance in processes that involve the transport of ions (such as electro-deionization) than the transport of water (electroosmosis).
已经使用分子动力学方法进行了分子模拟，以研究外电场对水合离子在水溶液中的迁移率、漂移速度和漂移扩散率的影响。这些性质对于一系列过程至关重要，包括电渗析、电去离子、电泳和电渗透。我们的研究结果表明，外电场会使水合离子结构在比溶液中大多数其他弛豫过程（通常为 1 ps 左右）长得多的时间尺度上弛豫（在 300 到 800 ps 之间）。以前的研究没有考虑到这种更长的弛豫时间，因此即使在非常高的电场下，也没有观察到离子的这种行为。外电场还必须克服几个（至少两个或更多）的活化能势垒，才能显著改变水合离子的结构。因此，动态行为几乎是以带的形式而不是线性地随电场强度变化。最后，电场对水的影响比对离子的影响小得多。因此，在外电场对水的影响比对离子的影响小得多。因此，在外电场对离子的输运（如电去离子）过程中，电场的影响将比水的输运（电渗透）过程更为显著。
