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实验测定了不同吸附剂浓度下,高岭土对Pb(Ⅱ)和Cu(Ⅱ)的吸附作用,结果表明存在明显的吸附剂浓度效应,即吸附等温线随吸附剂浓度升高而降低.采用传统的Langmuir吸附等温式对实验数据进行拟合表明,此等温式可准确地描述给定吸附剂浓度下的吸附结果,但不能预测其吸附剂浓度效应.根据表面组分活度(SCA)模型,假设吸附剂颗粒间存在相互作用,吸附剂表面吸附位的活度系数不等于1,而应为吸附剂浓度的函数,推导出了一个与吸附剂浓度有关的Langmuir(Langmuir-SCA)方程.运用高岭土吸附Pb(Ⅱ)和Cu(Ⅱ)以及文献中蛭石吸附Zn(Ⅱ)和Cd(Ⅱ)、咖啡吸附Pb(Ⅱ)的实验数据检验方程的适用性,结果表明Langmuir-SCA方程可准确地描述所观察到的吸附剂浓度效应.方程的两个内禀参数,热力学平衡常数(Keq)和特征饱和吸附量(Γ0m),与吸附剂浓度无关,并可由吸附实验数据拟合求得.
The adsorption of Pb (Ⅱ) and Cu (Ⅱ) by kaolinite at different concentrations of adsorbents was measured experimentally. The results showed that there was a significant concentration effect of adsorbents, that is, the adsorption isotherms decreased with the increase of adsorbents concentration. The fitting of experimental data by Langmuir isotherm shows that this isothermal equation can accurately describe the adsorption results for a given concentration of adsorbent but not for the adsorbent concentration effect.According to the Surface Component Activity (SCA) model, it is assumed There is interaction between the adsorbent particles, and the activity coefficient of the adsorption sites on the adsorbent surface is not equal to 1, but rather a function of the concentration of the adsorbent. A Langmuir-SCA equation relating to the concentration of the adsorbent is derived. The applicability of adsorption of Pb (Ⅱ) and Cu (Ⅱ) as well as the adsorption of Zn (Ⅱ) and Cd (Ⅱ) by vermiculite and Pb (Ⅱ) adsorption on coffee were tested by the experimental data. The results show that the Langmuir-SCA equation can accurately The observed effect of adsorbent concentration is described.The two intrinsic parameters of the equation, the thermodynamic equilibrium constant (Keq) and the characteristic saturated adsorption (Γ0m), are independent of the concentration of the adsorbent and can be fitted by the experimental adsorption data.