Sohn Seungman, Kim Dongsu
Department of Chemical Engineering, Virginia Tech., Blacksburg, VA 24061, USA.
Chemosphere. 2005 Jan;58(1):115-23. doi: 10.1016/j.chemosphere.2004.08.091.
The Langmuir isotherm, originally derived for the adsorption of gas molecules on solid surfaces, was modified to fit the adsorption isotherm of solutes onto solid surfaces in solution systems. The aim of this modification is based on the fact that direct application of the Langmuir isotherm to solution systems often leads to poor data fitting. In the present communication, it is shown that the level of data fitting to the Langmuir isotherm of literature data can be improved by a simple modification introducing a concentration dependent factor, X. The key concept of the modification lies in that the concentration of solute affects both adsorption and desorption stages. As a first approximation, we adopted a single-term polynomial for both processes of adsorption and desorption. Based on reanalysis of literature data of adsorption in solution, we confirmed that indeed the modified Langmuir isotherm more accurately describes the experimental observations. Furthermore, we proposed that the concentration dependent factor could be associated with the surface heterogeneity index that was introduced in a few other modified Langmuir isotherms. Some advantages and limitations of proposed modified Langmuir isotherm are also discussed.
朗缪尔等温线最初是为描述气体分子在固体表面的吸附而推导出来的，后来经过修改以适用于溶液体系中溶质在固体表面的吸附等温线。这种修改的目的是基于这样一个事实，即直接将朗缪尔等温线应用于溶液体系往往会导致数据拟合效果不佳。在本通讯中，表明通过引入一个与浓度相关的因子X进行简单修改，可以提高文献数据与朗缪尔等温线的数据拟合水平。修改的关键概念在于溶质浓度对吸附和解吸阶段都有影响。作为一阶近似，我们对吸附和解吸过程都采用了单项多项式。基于对溶液中吸附文献数据的重新分析，我们证实修改后的朗缪尔等温线确实能更准确地描述实验观察结果。此外，我们提出与浓度相关的因子可能与其他一些修改后的朗缪尔等温线中引入的表面非均质性指数有关。还讨论了所提出的修改后的朗缪尔等温线的一些优点和局限性。
