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BET theory
About: BET theory is a research topic. Over the lifetime, 9046 publications have been published within this topic receiving 286142 citations.
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TL;DR: In this article, the authors focus on how the BET equation is applicable to microporous adsorbents and find that the concept of "BET monolayer content" is misleading and could well be replaced by that of strong retention capacity.
Abstract: This chapter focuses on how the BET equation is applicable to microporous adsorbents. The BET method can be considered, essentially, as a mathematical means to analyze the adsorption isotherm to derive a “monolayer capacity” and then a surface area. The BET method should not be applied to adsorbents containing micropores in every case. Beyond the “linearity criterion” of the BET plot, two other criteria are found necessary, especially in the presence of micropores, to draw the specific advantage of the BET equation. Calorimetric data for adsorption on microporous adsorbents confirm the fact that the BET monolayer content mostly corresponds to the adsorbate in energetical interaction with the surface. For adsorbents containing micropores, the concept of “BET monolayer content” is misleading and could well be replaced by that of “BET strong retention capacity.” This concept includes the adsorbate present in the micropores together with the content of the statistical monolayer on the non-microporous portion of the surface.
810 citations
TL;DR: In this article, an exothermic peak at ca. 723 K in the DSC pattern was assigned to the crystallization of amorphous phase to anatase, and its heat was used to evaluate the weight fraction.
Abstract: Titanium(IV) oxide (TiO2) powders of various amorphous−anatase compositions were prepared by heat treatment (573−1073 K) of amorphous TiO2 in air and characterized by differential scanning calorimetry (DSC), powder X-ray diffraction (XRD), and BET surface area measurements. An exothermic peak at ca. 723 K in the DSC pattern was assigned to the crystallization of amorphous phase to anatase, and its heat was used to evaluate the weight fraction of amorphous phase. The fraction of anatase crystallites (f(anatase)) was calculated as the remainder after the amorphous phase and contaminated water or organic residue. The XRD data showed that the size of anatase crystallites was slightly decreased but almost constant along with the increase in f(anatase), being consistent with the small change in the BET surface area. These results suggest that each amorphous particle transforms into an anatase crystallite of similar size without sintering or crystal growth. The particles of mixture of amorphous and anatase were ...
782 citations
TL;DR: In this paper, three different carbonaceous materials, activated carbon, graphene oxide, and multi-walled carbon nanotubes, were modified by nitric acid and used as adsorbents for the removal of methylene blue dye from aqueous solution.
Abstract: Three different carbonaceous materials, activated carbon, graphene oxide, and multi-walled carbon nanotubes, were modified by nitric acid and used as adsorbents for the removal of methylene blue dye from aqueous solution. The adsorbents were characterized by N2 adsorption/desorption isotherms, infrared spectroscopy, particle size, and zeta potential measurements. Batch adsorption experiments were carried out to study the effect of solution pH and contact time on dye adsorption properties. The kinetic studies showed that the adsorption data followed a pseudo second-order kinetic model. The isotherm analysis indicated that the adsorption data can be represented by Langmuir isotherm model. The remarkably strong adsorption capacity normalized by the BET surface area of graphene oxide and carbon nanotubes can be attributed to π–π electron donor acceptor interaction and electrostatic attraction.
716 citations
TL;DR: In this paper, the first porous metal-organic framework solid incorporating Mg2+ ions, Mg3(NDC)3(DEF)4 (NDC = 2,6-naphthalenedicarboxylate, DEF = N,N-diethylformamide, 1), was reported.
Abstract: The synthesis of Mg3(NDC)3(DEF)4 (NDC = 2,6-naphthalenedicarboxylate, DEF = N,N-diethylformamide, 1), the first porous metal−organic framework solid incorporating Mg2+ ions, is reported. Its structure consists of linear Mg3 units linked via NDC bridges to form a three-dimensional framework, featuring one-dimensional channels filled with DEF molecules. Significantly, its framework is fully analogous to that observed within Zn3(NDC)3(CH3OH)2·2DMF·H2O (2), demonstrating that Mg2+ ions can directly substitute for the heavier Zn2+ ions. Compound 1 is readily desolvated by heating at 190 °C to give the microporous solid Mg3(NDC)3, exhibiting a BET surface area of 190 m2/g. Adsorption isotherms measured at 77 and 87 K indicate high H2 adsorption enthalpies in the range 7.0−9.5 kJ/mol, depending on the degree of loading. In addition, the material displays selective adsorption of H2 or O2 over N2 or CO, suggesting possible applications in gas separation technologies.
704 citations
TL;DR: In this paper, the effect of different preparation variables on the final porous texture is discussed, such as KOH/anthracite ratio, heating rate, carbonization temperature and carbonization time.
683 citations