This work is part of the effort at the Facility for Adsorbent Characterization and Testing (FACT lab) at the National Institute of Standards and Technology (NIST) to develop reference materials, reference data, and measurement best practices for adsorption metrology. High-pressure surface excess isotherms for CO2 adsorption on NIST Reference Material 8852 (ammonium ZSM-5) at 15 °C, 25 °C, and 35 °C

Dual reflux pressure swing adsorption is a peculiar application of pressure swing adsorption with relevant separation potential. In a proper range of operating parameters, high separation performances are achieved in many applications, including complete separation in the case of binary mixtures. In this work, a new representation of the design parameters suitable for complete separation based on the

Adsorbed methane significantly affects shale gas reservoir estimates and shale gas transport in shale formations. Hence, a practical model for accurately representing methane adsorption behavior at high-pressure and high-temperature in shale is imperative. In this study, a reliable mathematical framework that estimates the absolute adsorption directly from low-pressure excess adsorption data is applied

The effect of immobilized \(\upbeta\)-cyclodextrin (bCD) molecules inside a mesoporous silica support on the uptake of benzene and p-nitrophenol from aqueous solution was investigated using all-atom molecular dynamics (MD) simulations. The calculated adsorption isotherms are discussed with respect to the free energies of binding for a 1:1 complex of bCD and the aromatic guest molecule. The adsorption

A nonwoven fabric of konjac glucomannan (KGM) containing double stranded DNA molecules was fabricated by using the electro-spinning method and followed by crosslinking of KGM with 1,6-diisocyanatohexane. The adsorption of acridine orange (AO), as a model carcinogen, to the fabric was measured and analyzed by using a phenomenological theory. The fabric adsorbed AO quantitatively according to a hybrid

Technologies for control of indoor air quality are very important to ensure that health and comfort conditions are attained in closed environments. The indoor air quality market is fertile ground for adsorption technologies, both at larger industrial scale and for residential uses. The common strategy to design adsorption technologies considers constant inlet conditions, while for most indoor air control

Metal hydrides are promising hydrogen storage materials. Their extraordinary hydrogen adsorption capacity and selectivity make them ideal adsorbents for hydrogen purification. In particular, Mg-based materials demonstrate ultrahigh adsorption capacity and the starting materials are widely available. However, the utilization of metal hydrides in gas purification is limited due to surface poisoning which

Adsorption of methane on three Sichuan Basin shales at 318 K, 338 K, and 358 K has been investigated experimentally. The adsorption equilibrium isotherm data were fitted with Langmuir, DR and DA model. A thermodynamic model on heat of adsorption (Qst), considering the non-ideality of gas and the adsorbed phase specific volume, was developed for adsorption fields of methane and shales. The other thermodynamic

A novel bio-based activated carbon was synthesized from vine shoot, an agricultural waste, by chemical activation method using NaOH as activating agent. Adsorption of acetone, butanol and ethanol (ABE), as main products in ABE fermentation, in the single and multicomponent systems were measured. The experiments were carried out in both equilibrium and dynamic conditions and selectivity of the adsorbent

There is a well-known relationship between porous materials performance in a given process and their textural properties. These properties include specific surface area, among others, where the most widely used experimental technique to determine them is gas adsorption. Although the most used adsorptive gas is N2 at 77 K up to atmospheric pressure, its quadrupole moment generates specific interactions

A modified Poisson–Boltzmann model (PBEm) can be successfully used to determine the binding strength parameter, i.e., (Henry constant, K), for the protein adsorbent interaction in ion-exchanger columns. Lysozyme has been employed as a standard protein for the adsorption in a mesoporous silica adsorbent. The density of aminoacid groups and silanol groups were used as inputs to calculate the protein

To investigate the influence of fluid purity on the adsorption properties, adsorption kinetics and adsorption equilibria of two methanol samples with different water content on an activated carbon were studied. The purity of the methanol samples was 98.5% and 99.9%. Measurements were conducted at 298 K and 318 K using a magnetic suspension balance and cover a wide p/p0 range. To determine effective

The scanning hysteresis loop provides information about the correlation of the pore network, its connectivity and pore size distribution; nonetheless, this correlation cannot be revealed from the complete isotherm. To analyze the connectivity of the porous network in ordered mesoporous materials modified with iron and cobalt oxides, Ar adsorption–desorption isotherms and their corresponding scanning

The in-situ coating of zeolite crystals on Al2O3–SiO2 glass fiber was investigated using two commercial fibers (FB1 and FB2). The fibers were submitted to hydrothermal treatment at different temperatures, resulting in the crystallization of zeolite on their surfaces. The materials obtained were characterized by X-ray fluorescence, X-ray diffraction, Fourier transform infrared spectroscopy and scanning

Mesoporous silicas are known to be high-performing water adsorbents in high humidity levels due to their large pore volumes. However, for low humidity conditions, these materials typically present a less expressive performance, which is a drawback for many applications. In the present report, mesoporous silica SBA-15 was functionalized with Al, Ti, Zr and Li in order to improve their performance in

Methane adsorption on a recuperated activated carbon, AR-V, was studied over the temperature range of 213–393 K and at pressures up to 10 MPa from the perspective of its potential application for adsorption-based storage and separation technologies. The porous structure, phase and chemical compositions of AR-V were examined by nitrogen adsorption at 77 K, x-ray diffraction, and scanning electron microscopy

Zeolites are widely employed in the industrial drying of gases by Temperature Swing Adsorption (TSA). In a typical TSA process, the adsorbent is packed in a fixed bed, which is sequentially subjected to a “cold” feed (adsorption) and a hot flush (desorption). Due to the hydrothermal stress, adsorbents may suffer from reduced drying capacity in long-term service. The aim of this work is to assess the

Water vapor adsorption is a process of great importance for several industries. Because of that, new materials formed by mesoporous silica with metallic heteroatom functionalization have been studied for water adsorption. This functionalization process is still little studied in the literature, with many topics remaining to be evaluated. One of them is how each functionalization method (grafting and

The density functional theory (DFT) has been applied to describe confined fluids with great success in the literature. However, the usual numerical methods to solve the Euler–Lagrange equations of the grand potential functional are inefficient, finding local minimum and making the convergence very costly for systems with high complexity. Therefore, we present new numerical methods to accelerate the

In their letter to the Editor Silva and Rodrigues assert that the apparent activation energy for a macropore diffusion controlled process should be similar to the heat of adsorption. This is true only for a linear system. The system under consideration (CO2—13X Zeolite pellets) is non-linear, so the slope of the isotherm will depend on both the fractional loading and the Henry constant, both of which

This paper analyses the growth of the adsorbed layer during the course of \(N_2\) adsorption verified in two types of elliptical pores, oblates and prolates, by means of the Broekhoff de Boer theory. The information provided by the value of the thickness of the adsorbed layer permits to characterize the geometrical features of the liquid–vapour interface at every stage of the isotherm, prior and at

A usual experimental procedure for evaluation of solid–liquid adsorption isotherm models consists in varying the initial concentration of adsorbate, while keeping constant the ratio between the solution volume and adsorbent mass. However, one may wonder whether the experimental design can be more efficient if this ratio is allowed to vary. For this reason, in the present work, D-optimal designs for

In this study seven adsorption azeotropes involving binary systems and zeolite-based adsorbents were systematically investigated. Pure component isotherms and mixed-gas adsorption data were taken from published literature except for the benzene–propene system on silicalite, which is newly presented in this work using molecular simulations. Experimental adsorbed phase composition and total amount adsorbed

Density Functional Theory (DFT) calculations were used to investigate the interaction of hydrogen and deuterium in different orientations with different adsorption sites in finite-size cluster models of Cu2(bmc)4 and Zn2(bmc)4 paddle wheels that cut out from two important metal organic frameworks (MOFs), Cu-BTC and Zn-BTC. DFT calculations in the context of Orca program package with B3LYP exchange

Volatile organic compounds (VOCs) pose an ever-growing threat on human health and environment. Predicting VOC affinity coefficient and consequently estimating activated carbon adsorption requires fundamental understanding of adsorbate-adsorbent interaction, shape and hydrophilicity effects. Hence, a model which expressed these three factors with molecular descriptors was investigated with Ridge and

At present, nitrogen production from air by pressure swing adsorption (PSA) is simulated almost exclusively at low product purity levels (< 99% N2). However, with increasing global demand for highly purified gases provided by energy-efficient separation processes the requirement for either extensive experimental research in the high-purity range or predictive computer simulations arises. This paper

Molecular diffusion in nanoporous materials can be understood as series of dynamic hopping or exchange motions of molecules between different discrete sites. Exchange NMR offers the spectral resolution to distinguish between these different sites, based on isotropic and anisotropic NMR interactions that manifest differences in the local chemical or structural environments of molecules at different

The water vapor and the silico-alumino-phosphate (SAPO-34) material has been recognized to be one of the better adsorbate-adsorbent pairs for the packed-bed adsorptive thermal energy storage (TES) systems for space heating applications. In this paper, operating conditions including the system construction materials selection, cooling methods of the system after regeneration, relative humidity (RH)

Nanoporous solids are ubiquitous in chemical, energy, and environmental processes, where controlled transport of molecules through the pores plays a crucial role. They are used as sorbents, chromatographic or membrane materials for separations, and as catalysts and catalyst supports. Defined as materials where confinement effects lead to substantial deviations from bulk diffusion, nanoporous materials

Surface properties of single wall carbon nanotubes (SWNT) subjected to different treatments were studied. Nitrogen, argon and carbon dioxide were used to study the adsorption properties and its influence by the presence of surface sites on SWNT, acid treated SWNT and heat treated SWNT. Special attention was paid to carbon dioxide adsorption, by means of adsorption microcalorimetry and Monte Carlo simulation

We fabricated two types of single wall carbon nanotube (SWCNT) gels prepared by freeze-drying (cryogels) and air-drying (xerogels) from the dispersed SWCNT hydrogels. The comparative pore structure analysis using N2 adsorption at 77 K and H2O adsorption at 298 K was applied to these SWCNT gels. The N2 adsorption isotherms of both SWCNT gels have a steep initial uptake, low-pressure adsorption hysteresis

Two scenarios were investigated for predicting binary gas adsorption equilibria when the single gas isotherms of one component is described by the three process Langmuir (TPL) model and the single gas isotherms of the other component is described by either the dual process Langmuir (DPL) or single process Langmuir (SPL) model. For the TPL–SPL and TPL–DPL models, 7 and 12 different correlations of energetic

Gas adsorption at high pressures in porous solids is commonly quantified in terms of the excess amount adsorbed. Despite the wide spectrum of adsorbent morphologies available, the analysis of excess adsorption isotherms has mostly focused on microporous materials and the role of mesoporosity remains largely unexplored. Here, we present supercritical CO2 adsorption isotherms measured at \(T=308\) K

Magnetic resonance in the guise of conventional imaging (MRI, also known as k-space imaging) and diffusion imaging (q-space imaging) and combined k- and q-space imaging provides a powerful means of probing porous media and the dynamic processes occurring within such media. This article provides an overview of the imaging process and the accessible length scales of these techniques for probing porous

The two-region (“Kärger”) model of diffusion in complex pore spaces is exploited for quantitating mass transfer in hierarchically organized nanoporous materials, consisting of a continuous microporous bulk phase permeated by a network of transport pores. With the implications that the diffusivity in the transport pores significantly exceeds the diffusivity in the micropores and that the relative population

The frequency response (FR) method, a pseudo-steady state relaxation technique employing perturbation frequency, plays an essential role in discriminating between multi-kinetic mechanisms in microporous materials for separation and catalytic processes. Experimental and theoretical principles are reviewed for three frequency response methods, including one commonly used batch system with volume perturbation

Landfill gas (LFG) produced from municipal solid waste substrates represents an important source of RNG and the market for its upgrade is facing significant challenges in terms of energy consumption and operating costs. To ensure higher CH4 yields and avoid its release in the atmosphere, the LFG is collected below the atmospheric pressure by the use of a vacuum pump that results in the contamination

Recently, we presented a detailed and systematic molecular simulation study of the effect of point charges on adsorption of carbon dioxide and water in a series of typical MOF materials [1]. Unfortunately, we have since detected a mistake in one of the input files pertaining to water adsorption isotherm simulations—concretely, the structure of the water molecule was modelled as linear instead of obeying

Anthropogenic CO2 emissions are the major drivers of global warming and climate change. The adsorption of CO2 is one of the strategies to mitigate these emissions. In this sense, different materials have been used as adsorbents as is the case of zeolites. In this work,experimental infrared and X-ray analyses together with DFT (Density Functional Theory)theoretical calculations were employed to study

A novel single-bed, “Snap-on” and standalone, medical oxygen concentrator design based on a rapid pressure swing adsorption process was investigated for continuous oxygen supply. The Snap-on concentrator design is easy to hook up to an existing compressed air source, and the unit can then be readily used to produce oxygen for medical applications. It is easily transportable and compared to a traditional

Nanoporous solids, including microporous, mesoporous and hierarchically structured porous materials, are of scientific and technological interest because of their high surface-to-volume ratio and ability to impose shape- and size-selectivity on molecules diffusing through them. Enormous efforts have been put in the mechanistic understanding of diffusion–reaction relationships of nanoporous solids,

It has come to our attention that the following sentence contains an error: “However, while the octahedra in MIL-53 are cis-connected, the octahedra in CAU-10 are trans-connected.” The words “cis” and “trans” should be swapped to read “However, while the octahedra in MIL-53 are trans-connected, the octahedra in CAU-10 are cis-connected.”