Do D D, Do H D
Department of Chemical Engineering, University of Queensland, St. Lucia, Qld 4072, Australia.
J Colloid Interface Sci. 2005 Jul 15;287(2):452-60. doi: 10.1016/j.jcis.2005.02.039.
In this paper we investigate the effects of surface mediation on the adsorption behavior of argon at different temperatures on homogeneous graphitized thermal carbon black and on heterogeneous nongraphitized carbon black surface. The grand canonical Monte Carlo (GCMC) simulation is used to study the adsorption, and its performance is tested against a number of experimental data on graphitized thermal carbon black (which is known to be highly homogeneous) that are available in the literature. The surface-mediation effect is shown to be essential in the correct description of the adsorption isotherm because without accounting for that effect the GCMC simulation results are always greater than the experimental data in the region where the monolayer is being completed. This is due to the overestimation of the fluid-fluid interaction between particles in the first layer close to the solid surface. It is the surface mediation that reduces this fluid-fluid interaction in the adsorbed layers, and therefore the GCMC simulation results accounting for this surface mediation that are presented in this paper result in a better description of the data. This surface mediation having been determined, the surface excess of argon on heterogeneous carbon surfaces having solid-fluid interaction energies different from the graphite can be readily obtained. Since the real heterogeneous carbon surface is not the same as the homogeneous graphite surface, it can be described by an area distribution in terms of the well depth of the solid-fluid energy. Assuming a patchwise topology of the surface with patches of uniform well depth of solid-fluid interaction, the adsorption on a real carbon surface can be determined as an integral of the local surface excess of each patch with respect to the differential area. When this is matched against the experimental data of a carbon surface, we can derive the area distribution versus energy and hence the geometrical surface area. This new approach will be illustrated with the adsorption of argon on a nongraphitized carbon at 87.3 and 77 K, and it is found that the GCMC surface area is different from the BET surface area by about 7%. Furthermore, the description of the isotherm in the region of BET validity of 0.06 to 0.2 is much better with our method than with the BET equation.
在本文中，我们研究了表面介导对氩气在不同温度下在均匀石墨化热炭黑和非均匀非石墨化炭黑表面吸附行为的影响。采用巨正则蒙特卡罗（GCMC）模拟研究吸附过程，并根据文献中现有的一些关于石墨化热炭黑（已知其高度均匀）的实验数据对其性能进行了测试。结果表明，表面介导效应对于正确描述吸附等温线至关重要，因为如果不考虑该效应，GCMC模拟结果在单层形成区域总是大于实验数据。这是由于对靠近固体表面的第一层中颗粒间的流体 - 流体相互作用估计过高。正是表面介导降低了吸附层中的这种流体 - 流体相互作用，因此本文给出的考虑了这种表面介导的GCMC模拟结果能更好地描述数据。确定了这种表面介导后，就可以很容易地得到氩气在具有与石墨不同的固 - 液相互作用能的非均匀碳表面上的表面过剩量。由于实际的非均匀碳表面与均匀石墨表面不同，可以根据固 - 液能阱深度的面积分布来描述它。假设表面具有斑块状拓扑结构，且斑块具有均匀的固 - 液相互作用阱深度，则真实碳表面上的吸附可以确定为每个斑块的局部表面过剩量相对于微分面积的积分。当将其与碳表面的实验数据进行匹配时，我们可以得出面积分布与能量的关系，从而得到几何表面积。将用氩气在87.3K和77K下在非石墨化碳上的吸附来说明这种新方法，结果发现GCMC表面积与BET表面积相差约7%。此外，在BET有效性范围0.06至0.2内，我们的方法对等温线的描述比BET方程要好得多。
