On the surface tension and Zeta potential of electrolyte solutions.
On the surface tension and Zeta potential of electrolyte solutions.
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DOI：
10.1016/j.cis.2016.06.006
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发表时间：
2017-06
影响因子：
15.6
通讯作者：
M. Manciu;F. Manciu;E. Ruckenstein
中科院分区：
文献类型：
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作者：
M. Manciu;F. Manciu;E. Ruckenstein
空气/水界面附近的离子分布仍然是一个有争议的问题，大量的计算和实验提供了相互矛盾的结果，甚至关于界面或本体水的简单离子（如H+和OH−）的偏好。当离子和界面之间的短程相互作用被假定为独立于体相浓度时，如果它们与表面张力数据相容，则它们低估了实验Zeta电位的数量级。如果他们是兼容的Zeta电位数据，他们是在强烈不同意与表面张力实验。有人建议，这些观察结果可能是由于相对较低数量的界面水分子可水合的离子和各种离子之间的吸附位点的竞争。因此，尽管在低本体浓度下，结构破坏离子优选界面，但在足够大的本体浓度下，这些离子的表面吸附变得饱和，并且它们的界面浓度可能变得低于本体中的浓度。因此，离子与界面的总相互作用在低体积浓度下可以是强烈吸引的，而在高浓度下吸引力较小（甚至排斥）。为了模拟这种效应，通过OH-和Cl-的修改后的朗缪尔吸附表达式来考虑离子和界面之间的相互作用，而H+离子被认为附着在任何界面水分子上，即使后者参与水合。阴离子。这里采用的吸附的简单模型是在协议与Zeta电位和表面张力的实验，并可能揭示的条件下，一个给定的离子表现出的倾向，无论是空气/水界面，或散装水。
The distribution of ions in the vicinity of the air/water interface is still a matter of strong debate, with numerous calculations and experiments providing contradictory results, even regarding the preference of simple ions (such as H+and OH−) for interfacial or bulk water. When short range interactions between ions and the interface are assumed independent of bulk concentrations, if they are compatible with the surface tension data, they underpredict the experimental Zeta potentials by orders of magnitude. If they are compatible with Zeta potential data, they are in strong disagreement with surface tension experiments. It is suggested that these observations might be a result of the relatively low number of interfacial water molecules available to hydrate the ions and the competition between various ions for adsorption sites. Therefore, whereas at low bulk concentrations, the Structure-Breaking ions prefer the interface, at sufficiently large bulk concentrations the surface adsorptions of these ions become saturated, and their interfacial concentrations may become lower than in the bulk. Consequently, the total interactions of ions with the interface can be strongly attractive at low bulk concentrations, and less attractive (or even repulsive), at high concentrations. To model this effect, the interactions between ions and interface are taken into account via modified Langmuir adsorption expressions for OH−and Cl−, while the H+ions are considered to be attached to any interfacial water molecule, even if the latter participate in the hydration of anions. The simple model of adsorption employed here is in agreement with both experiments on Zeta potential and on surface tension, and might reveal the conditions under which a given ion exhibits propensity for either the air/water interface, or for bulk water.