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Approach to Estimation of Hamaker Constant as Taking Hofmeister Effects into Account
The Journal of Physical Chemistry C ( IF 3.3 ) Pub Date : 2018-04-10 00:00:00 , DOI: 10.1021/acs.jpcc.7b12830
Yaxue Luo 1 , Xiaodan Gao 2 , Rui Tian 1 , Hang Li 1
Affiliation  

The Hamaker constant is an important material parameter for both the description of particle interaction and the prediction of colloidal stability. Existing methods based on the classic Derjaguin–Landau–Verwey–Overbeek theory ignore the Hofmeister effects and would derive flawed results. In this article, approaches to the estimation of the Hamaker constant with and without consideration of the Hofmeister effects were, respectively, suggested, where the Hamaker constant was obtained on the basis of the mathematic relationship between electrostatic repulsive and van der Waals attractive interaction at the critical coagulation concentration (CCC) by using the dynamic light scattering technique. It indicated that the montmorillonite particles aggregation kinetics in the presence of Li+, K+, and Cs+ exhibited remarkable Hofmeister effects and the CCC values show: Li+ (277.2 mM) > K+ (80.3 mM) > Cs+ (27.2 mM). Without consideration of Hofmeister effects, completely distinct Hamaker constants for the same material were obtained from aggregation kinetics of the three cations (6.70, 17.4, and 35.7 × 10–20 J for Li+, K+, and Cs+ system, respectively). Obviously, it is unacceptable because the obtained Hamaker constant values should be the same for the same montmorillonite. In contrast, by taking the Hofmeister effects into account, consistent Hamaker constants (6.20, 6.09, and 6.75 × 10–20 J for Li+, K+ and Cs+ system, respectively) could be derived and reached in good agreement with results reported in the literature. Our study proved that Hofmeister effects deeply affect the solid/liquid interface process of nano-/microsized particles and only by taking the Hofmeister effects into account could we get the reliable Hamaker constant and correctly describe particle interaction.

中文翻译:

考虑Hofmeister效应的Hamaker常数估计方法。

Hamaker常数是用于描述粒子相互作用和预测胶体稳定性的重要材料参数。现有基于经典Derjaguin–Landau–Verwey–Overbeek理论的方法忽略了Hofmeister效应,并会得出有缺陷的结果。在本文中,分别提出了在没有考虑霍夫迈斯特效应的情况下估计Hamaker常数的方法,其中Hamaker常数是根据静电排斥力与范德华力在吸附力相互作用下的数学关系而获得的。通过使用动态光散射技术获得临界凝结浓度(CCC)。表明在Li +,K +存在下蒙脱土颗粒的聚集动力学。,Cs +表现出显着的霍夫迈斯特效应,CCC值显示:Li +(277.2 mM)> K +(80.3 mM)> Cs +(27.2 mM)。不考虑霍夫迈斯特效应,从三种阳离子的聚集动力学(对于Li +,K +和Cs +系统,分别为6.70、17.4和35.7×10 –20 J)获得了完全不同的Hamaker常数。显然,这是不可接受的,因为对于相同的蒙脱石,获得的Hamaker常数值应该相同。相反,通过考虑霍夫迈斯特效应,可以得到一致的Hamaker常数(6.20、6.09和6.75×10 –20分别得出Li +,K +和Cs +系统的J值,并与文献报道的结果高度吻合。我们的研究证明,霍夫迈斯特效应深刻影响纳米/微米级颗粒的固/液界面过程,只有考虑霍夫迈斯特效应,我们才能获得可靠的Hamaker常数并正确描述颗粒之间的相互作用。
更新日期:2018-04-10
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