Investigation of activated carbon surface heterogeneity by argon and nitrogen low-pressure quasi-equilibrium volumetry.
Investigation of activated carbon surface heterogeneity by argon and nitrogen low-pressure quasi-equilibrium volumetry.
复制标题
通过氩和氮低压准平衡体积法研究活性炭表面异质性。
作者：
C. Garnier;T. Gorner;A. Razafitianamaharavo;F. Villieras
表面不均匀性可以通过不同气体探针在固体材料上的吸附来评估。在本研究中，通过经典的N2 Brunauer-Emmett-Teller（BET）测量和低压准平衡容量法（LPQEV）（Villieras，F.;米绍湖J.道：Bardot，F.; Cases，J.M.; Francois，M.; Rudzinski，W. Langmuir 1997，13，1104）。应用了三种数据评估方法：（a）Frenkel-Halsey-Hill方法，用于从BET数据估计分形维数;（B）Horwath-Kawazoe方法，用于从LPQEV Ar和N2吸附等温线计算孔径分布;以及（c）导数等温线总和（DIS）方法，用于通过局部导数等温线的概念描述固体的表面不均匀性。类似的Ar和N2的吸附能分布上得到所有的碳，这表明存在主要是非极性表面。当吸附由货车德瓦尔斯方程描述时，不同能量位与氩和氮的相互作用能之间的比率为0.88。该值对应非常好的斜率时得到的Ar和N2的位置的局部等温线的DIS方法进行了比较。这种关系具有重要的影响，因为它使人们能够约束局部等温线的建模。这项研究，除了表面的信息，显示了很大的可能性DIS方法的表面分析，不仅在固体非均质性表征，但也在极性评估方面。
Surface heterogeneity can be assessed by adsorption of different gaseous probes on solid materials. In the present study, four types of activated carbons were analyzed by classical N2 Brunauer-Emmett-Teller (BET) measurements and by low-pressure quasi-equilibrium volumetry (LPQEV) (Villieras, F.; Michot, L. J.; Bardot, F.; Cases, J. M.; Francois, M.; Rudzinski, W. Langmuir 1997, 13, 1104). Three methods of data evaluation were applied: (a) the Frenkel-Halsey-Hill method for estimation of fractal dimensions from BET data, (b) the Horwath-Kawazoe method to calculate the pore size distribution from LPQEV Ar and N2 adsorption isotherms, and (c) the derivative isotherm summation (DIS) method to describe the solid's surface heterogeneity by a concept of local derivative isotherms. Similar Ar and N2 adsorption energy distributions were obtained on all carbons, which indicates the presence of mainly nonpolar surfaces. When adsorption was described by the van der Waals equation, the ratio between the interaction energy of different energetic sites with argon and nitrogen was 0.88. This value corresponded very well with a slope obtained when Ar and N2 positions of local isotherms by the DIS method were compared. This relationship has an important impact because it enables one to constrain the modeling of local isotherms. This study, besides the surface information, showed large possibilities of the DIS method for the surface analysis not only in terms of solid heterogeneity characterization but also in terms of polarity assessment.