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Gibbsian interpretation of Langmuir, Freundlich and Temkin isotherms for adsorption in solution
Philosophical Magazine Letters ( IF 1.2 ) Pub Date : 2022-06-20 , DOI: 10.1080/09500839.2022.2084571
Lei Lu 1 , Chongzheng Na 1
Affiliation  

ABSTRACT

Adsorption is a physicochemical phenomenon important in both natural and engineering processes. In the research and practice of adsorption equilibrium, a long-standing challenge is how to reconcile the classical models proposed by Gibbs, Langmuir, Freundlich, and Temkin for interpreting experimentally obtained adsorption isotherms. Here, we show that the Langmuir, Freundlich, and Temkin isotherms can be derived from the Gibbs equation under different conditions for the change of surface energy (a.k.a. surface tension) by adsorption. When the change of surface energy is predominantly controlled by the change of chemical potential with negligible contribution from the change of internal energy and entropy, the Gibbs equation can be integrated to give the Langmuir isotherm. When changes of internal energy and entropy are no longer negligible, the integration of the Gibbs equation gives the Freundlich and Temkin equations, according to a change of surface energy either independent or linearly dependent on the adsorption capacity. These results indicate that the classical models share the common mechanism of phase equilibrium described by the Gibbsian thermodynamics, thereby providing novel insights for their application.



中文翻译:

溶液中吸附的 Langmuir、Freundlich 和 Temkin 等温线的 Gibbsian 解释

摘要

吸附是一种在自然和工程过程中都很重要的物理化学现象。在吸附平衡的研究和实践中,一个长期存在的挑战是如何协调 Gibbs、Langmuir、Freundlich 和 Temkin 提出的用于解释实验获得的吸附等温线的经典模型。在这里,我们展示了 Langmuir、Freundlich 和 Temkin 等温线可以从 Gibbs 方程在不同条件下通过吸附改变表面能(又称表面张力)得到。当表面能的变化主要由化学势的变化控制,而内能和熵的变化的贡献可以忽略不计时,可以将 Gibbs 方程积分得到 Langmuir 等温线。当内能和熵的变化不再可以忽略时,根据表面能的变化,Gibbs 方程的积分给出了 Freundlich 和 Temkin 方程,该变化与吸附容量无关或线性相关。这些结果表明,经典模型共享吉布斯热力学描述的相平衡的共同机制,从而为其应用提供了新的见解。

更新日期:2022-06-20
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