Adsorption thermodynamics may be developed in a manner that is symmetric. The quantities ΔḠ1, ΔH̄1 and ΔS̄1 exist, along with the quantities ΔḠ2, ΔH̄2 = qst, and ΔS̄2 (subscripts one and two denoting adsorbent and adsorbate, respectively) that are usually calculated. The formalism of Copeland and Young [Adv. Chem. 33, 348 (1961)] is used to calculate the entire set from the data of Drain and Morrison [Trans. Faraday Soc. 49, 654 (1953)] and from various common adsorption models. The Drain and Morrison data for nitrogen on rutile could be fit with a set of eight Langmuirian patches. Importantly, the fit was based on the calorimetric heat of adsorption data as providing more precision than the adsorption data in the region of high coverage. Eight patches were sufficient to fit the entire set of data in the submonolayer region to within experimental error; thus any attempt to discern a finer structure to the patch distribution would be illusory. The physical meaning of a ΔH̄1 is discussed, as well as the nature of its relation to ΔH̄2. Experiments are described whereby direct measurement of ΔH̄1 and of ΔḠ1 might be possible.

In this paper, we have realized three adsorption isotherms of the ruthenium-based dye molecules, cisdi (thiocyanato)bis (2,2′bipyridyl-4,4′-dicarboxylate)ruthenium (II) (N3) into the mesoporous TiO2 (anatase) at three different temperatures:298.15, 313.15 K and 333.15 K using the UV–vis spectroscopy method. These adsorption isotherms have been simulated using several models established through a statistical physics formalism in order to involve in model expressions some parameters which have physicochemical meaning and to better interpret information about the adsorption process at the molecular level. A multilayer model was determined to best reproduce and simulate the experimental data. In this model, five parameters affecting the adsorption process have been adjusted, namely the number of molecules per adsorption site n, the density of receptor sites Nm, the two energetic parameters: the concentrations at half saturation C1 and C2 and the number of layers NL. These parameters have been deduced from the fitting of the experimental adsorption isotherms by numerical simulation. Thanks to the grand canonical ensemble in statistical physics, the energetic parameters suggest physical bonding of the N3 dye to the TiO2 surface in the case of low concentrations through monodentate and bidentate with hydrogen bond configurations. Finally, a new method based on Kelvin equation in the liquid phase is used to determine the pore size distribution (PSD) and the adsorption energy distribution (AED) of the mesoporous TiO2.

It is shown that a previously published procedure for obtaining site energy distributions can be applied to data which include multilayer adsorption, with the BET equation used as the local isotherm function. When applied to the adsorption of argon on rutile, the resulting distribution function is essentially the same as that obtained by Drain and Morrison using a nearly thermodynamic procedure. The BET model can thus be applied to adsorption on heterogeneous surfaces.

The physical adsorption of nitrogen at 77°K and 90°K is reported for the molecular solids ammonia, methanol, carbon dioxide, benzene, iodine, and bromine. The adsorption isotherms are similar to those previously observed with ice powder and the entire set of molecular solids appears to constitute a group of nonpolar, low-energy adsorbents.

Ice powder prepared at 77°K. gives nitrogen adsorption isotherms indicating a fairly uniform and not highly polar surface. Annealing at −70°C. leads to adsorption behavior characteristic of a nonpolar surface such as Teflon, and surface inertness towards nitrogen reaches an extreme in the case of snow samples.

The two principal criteria used to evaluate the physical nature of the physically adsorbed state, namely, fit-to-model isotherm equations and comparison of entropy quantities, are examined for the situation of a heterogeneous surface. It is concluded that even for quite homogeneous surfaces, the possibility of some heterogeneity offers enough scope to erase the differences between adsorption isotherms derived from different models.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTAdsorption of Nitrogen on Ice at 78°KArthur W. Adamson and Leon M. DormantCite this: J. Am. Chem. Soc. 1966, 88, 9, 2055–2057Publication Date (Print):May 1, 1966Publication History Published online1 May 2002Published inissue 1 May 1966https://pubs.acs.org/doi/10.1021/ja00961a044https://doi.org/10.1021/ja00961a044research-articleACS PublicationsRequest reuse permissionsArticle Views66Altmetric-Citations28LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts