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.”

Quasielastic neutron scattering (QENS) allows measurement of the molecular displacements in time and space, from pico- to tens of nanoseconds and from Ångstroms to nanometers, respectively. The method probes dynamics from fast vibrational modes down to slow diffusive motion. Every scattering experiment leads to a dynamic structure factor \(S\left( {\vec Q,\omega } \right)\) or its spatial and temporal

The analogy between heat uptake in a thermal regenerator and selective uptake of gas components in an adsorbent bed has inspired development of alternative architectures for adsorptive gas separation processes. An experimental laboratory sorption enhanced reaction approach for low pressure Haber-Bosch ammonia synthesis successfully used a Stirling engine mechanism to generate coordinated pressure swings

The recently developed thermodynamic Langmuir isotherm model is used to estimate the isosteric heat of adsorption for pure component adsorption. Specifically, pure component adsorption isotherms at different temperatures are first correlated with the thermodynamic Langmuir isotherm model. Then the pure component isosteric heat of adsorption is calculated with the Clausius–Clapeyron equation. We show

A general procedure has been developed for synthesizing four MOFs sharing similar chains of AlO6 octahedra (CAU-10, NOTT-300, MIL-53-TDC, and MIL-160). CAU-10 has been synthesized with eight differently substituted ligands to impart different characteristics into the pore space. Isotherms of CO2, CH4, and N2 were measured on all MOFs synthesized in this work to assess the effects of functional group

With increasing nitrogen purity, PSA plants require an over-proportional air demand with the consequence that high-purity PSA systems engender a distinct interest in energy-saving measures. This paper presents process intensification strategies with the focus on a reduced energy consumption. Therefore, the influence of PSA configuration and cycle organisation on process performance was investigated

Breakthrough curves of N2, O2, and Ar on Silver exchanged titanosilicates (Ag-ETS-10) extrudates and granules were measured using a laboratory scale dynamic column breakthrough (DCB) apparatus. In order to investigate the dynamics of the mass transfer, effect of flow rate, temperature and pressure on the composition and temperature curves were studied. In a separate attempt, N2 breakthrough curves

Labeling in diffusion measurements by pulsed field gradient (PFG) NMR is based on the observation of the phase of nuclear spins acquired in a constant magnetic field with purposefully superimposed field gradients. This labeling does in no way affect microdynamics and provides information about the probability distribution of molecular displacements as a function of time. An introduction of the measuring

The water crisis is one of the main global risks based on its societal impact, particularly the access to safe drinking water in regions with a dry (arid) or mainly dry (semi-arid) climate. Several techniques are being developed, namely the use of regenerative desiccant (e.g., MOFs) to water capture through adsorption processes. MIL-160(Al) belongs to the fumarate-based MOFs family, and it is one of

Excess adsorption of cyclohexanone, cyclohexanol and tert-butanol over metal–organic frameworks Cr-MIL-100 and structurally close Cr-MIL-101 from n-hexane was measured at room temperature. Apparent adsorption equilibrium constants were calculated under the assumption of monolayer adsorption. Two types of adsorption centers turned out to be enough to build a model of experimental isotherms for cyclohexanone

We present a coarse grained lattice gas model for the thermodynamics and dynamics of adsorption and desorption in three dimensionally ordered mesoporous carbons, originally developed as templates for the synthesis of zeolites with mesoporosity. We model these systems as an assembly of interconnected spherical pores in an fcc structure which are coarse grained on to a simple cubic lattice. The adsorption

To calculate a gas sorption isotherm from measurements made using the manometric (Sieverts) technique requires accurate knowledge of the sample cell void volume, the volume able to be occupied by the free gas. For many combinations of material and morphology, this volume changes as the sample expands or compresses, swells, undergoes chemical change or adsorbs gas. For gas adsorption measurements on

The rapid pressure swing adsorption (RPSA) technology has been widely used for applications including portable oxygen generators due to high O2 productivities and low bed size factors (BSF, total amount of adsorbent per ton of O2 produced per day, kg/TPDO2). The improvement of RPSA process has been a key issue for efficient O2 production in terms of its generally lower O2 recovery as compared to other

The availability of commercial gravimetric and volumetric systems for the measurement of adsorption equilibrium has seen also a growth of the use of these instruments to measure adsorption kinetics. A review of publications from the past 20 years has been used to assess common practice in 180 cases. There are worrying trends observed, such as lack of information on the actual conditions used in the

In this study we present a new methodology for correcting experimental Zero Length Column data, to account for contributions to the measured signal arising from extra-column volumes and the detector. The methodology considers the experimental setup as a series of mixing volumes with diffusive pockets whose contributions to the overall measured signal can be accurately described by simple model functions

Microimaging on the basis of, respectively, interference microscopy and IR microscopy permit the observation of the distribution of guest molecules in nanoporous solids and their variation with time. Thus attainable knowledge of both concentration gradients and diffusion fluxes provides direct access to the underlying diffusion phenomena. This includes, in particular, the measurement of transport diffusion

The effects of operating temperature on the performance of small scale oxygen concentrator were experimentally investigated using a rotary valve multi-column rapid cycle pressure swing adsorption (PSA) unit which produced a continuous stream of ≥ 90% O2 from compressed air. Simple cooling fans and air cylinder were used for controlling the temperature of compressed air. The change of column midpoint

This paper provides a general overview of the phenomenon of guest diffusion in nanoporous materials. It introduces the different types of diffusion measurement that can be performed under both equilibrium and non-equilibrium conditions in either single- or multicomponent systems. In the technological application of nanoporous materials for mass separation and catalytic conversion diffusion often has

By using the DFT and TD-DFT method, the potential of B12N12 nanocage to adsorb and detect of cyanogen fluoride (FCN) as a toxic gas molecule in the present of 1H+, 2H+, and 3H+ ions field and static electric field (SEF) were investigated at the WB97XD level of theory at the 6-31G (d, p) basis set. The structural and electrical parameters, adsorption energy, quantum descriptor, quantum theory of atom

Among the adsorption-based separation processes for gaseous mixtures, those exploiting pressure variations, so-called Pressure Swing Adsorption (PSA) processes, are the most popular. In this work, we focus on the specific PSA configuration known as Dual Reflux-Pressure Swing Adsorption (DR-PSA) given its ability to achieve sharp separations. In the case of binary mixtures, an analytical approach based

The zero length column technique has been developed over the past 30 years as a versatile experimental method to measure adsorption equilibrium and kinetics. In this review we discuss in detail the theory that forms the basis for the technique in order to understand how to design and operate efficiently a system. Experimental checks that should be performed to ensure the correct interpretation of the

This paper provides a set of comprehensive guidelines for the use of dynamic column breakthrough experiments to measure single and multi-component equilibria and kinetics. Recommendations are made for the design of the experimental rig, experimental procedures, and data processing methods to minimize errors and increase data reliability. Designing experiments to identify the transport mechanism, and

The scale of smelting ferronickel by RKEF (Rotary kiln—electric furnace) process is increasing these years, these untreated ferronickel slags will occupy a large area as accumulation and cause ecological damage. On the other hand, the CO2 emission and global warming are urgent problems to be solved as they have resulted in severe climate change. Carbon Capture and Storage (CCS) technology is considered

2H solid-state NMR represents a reliable method for probing the dynamics of the molecules in confined geometries, including microporous and mesoporous materials such as zeolites or metal–organic frameworks (MOFs). Dynamic characteristics derived from analyses of 2H NMR line shape and spin relaxation for adsorbed deuterated molecules can be related with translational motions along the porous framework

We present the development and application of X-ray Computed Tomography (CT) for the determination of the adsorption properties of microporous adsorbents and the study of breakthrough experiments in a laboratory fixed-bed adsorption column. Using the model system \(\text {CO}_2/\text {helium}\) on activated carbon, equilibrium and dynamic adsorption/desorption measurements by X-ray CT are described

Sorption processes are incorporated in a wide range of applications. A heat and mass transfer model which calculates the temperature distribution and pressure in a sorption cell is desired for developing any sorption system. In this paper, we present a one-dimensional dynamic numerical model for closed sorption cell systems, which is based on adsorption isotherm measurements of the working pair. The

The problem of measuring sorption kinetics in microporous adsorbents and distinguishing experimentally between surface resistance and internal diffusion is discussed and reviewed with reference to several commonly used experimental techniques; direct uptake rate measurements, zero length column (ZLC), frequency response, PFG NMR and interference microscopy.

To match the dynamics of a linear driving force model and the diffusion equation is of great practical importance in the design and optimization of adsorption separation processes. A frequency response analysis is applied to show that it is not possible to arrive at an equivalence based on a single parameter. Using this as the basis, a universal equivalence for the linear problem is constructed and

One primary measurement of open porosity uses physical adsorption isotherm, amount adsorbed versus gas pressure. Classical treatments, including the BET, cannot fit the isotherm for its full range, therefore standard curves have been created from non-porous materials for comparison. This classical method yields three output parameters, two surface areas, pore and external, relative to the standard

Based on the molecular understanding of the interplay of diffusion and adsorption, new membrane materials can be developed and the operational conditions of gas separation membranes can be optimized. Therefore, numerous diffusion and adsorption studies are conducted to optimize membrane materials. However, in an opposite way, transport or Fickian diffusion coefficients DT can be derived from membrane

The use of clay minerals for the decontamination of liquid radioactive waste generated during the work of nuclear energy enterprises remains currently relevant. The effect of the surface hydration of a montmorillonite nanocrystal on the adsorption of cesium and strontium ions from dilute solutions was studied. As opposed to the generally accepted mechanism of the adsorption of cesium and strontium

The insolubility of graphene nanosheets in aqueous media has been a limitation for the practical applications of this unique material. The non-covalent functionalization of graphene with mixed surfactants is an effective procedure for preparation of stable graphene dispersions. Physical adsorption of surfactants onto graphene surfaces is a significant stage in the dispersion of graphene nanosheets

Batch adsorption experiments are carried out by adding a known amount of adsorbent to a liquid solution at a known initial concentration and following the evolution in time of the concentration of the adsorbate. This is a very common method to obtain equilibrium and kinetic information in liquid systems, but in most cases kinetic results are analysed on the basis of empirical models. Two phenomenological

This paper reports the results of an international interlaboratory study led by the National Institute of Standards and Technology (NIST) on the measurement of high-pressure surface excess methane adsorption isotherms on NIST Reference Material RM 8850 (Zeolite Y), at 25 °C up to 7.5 MPa. Twenty laboratories participated in the study and contributed over one-hundred adsorption isotherms of methane

Adsorption and desorption of hydrocarbons in a realistic model (2496 atoms) of ZSM-5 zeolite (MFI), including an external surface and a reservoir for molecules, have been studied using classical molecular dynamics, with special focus on surface barriers. Different degrees of surface blocking have been modeled according to experimental observations. Using previous molecular dynamics results, from the

We had performed GCMC simulations to study the adsorption isotherms, the isosteric heats of argon, methane, nitrogen, carbon dioxide, methanol and water adsorption on molecular models of activated carbons at their boiling points in order to understand the contributions of the different functional groups of the adsorbent sites in the adsorption process. We had found that the values obtained from the

High magnetic fields (up to 17.6 T) in combination with large magnetic field gradients (up to 25 T/m) were successfully utilized in pulsed field gradient (PFG) NMR studies of gas and liquid diffusion in nanoporous materials. In this mini-review, we present selected examples of such studies demonstrating the ability of high field PFG NMR to gain unique insights and differentiate between various types

Gas separation by adsorption processes such as pressure swing adsorption (PSA) presents an attractive alternative for upgrading biogas to biomethane. A new vacuum pressure swing adsorption (VPSA) cycle is proposed for a unit designed to purify pre-cleaned biogas (40% CO2 and 60% CH4) in industrial conditions (feed flow rate more than 500 Nm3/h and large-volume equipment). The process simulations performed

Many decisions must be made when determining design and operation of a chromatographic process. Such decisions should optimize the performance, including product purity, recovery, productivity, and desorbent consumption. For this problem, model-based optimization has been shown to be a powerful approach, aided by recent developments in modeling of chromatographic processes. In this article, past studies

In this work, direct air capture (DAC) via adsorption is studied through the design and analysis of two temperature–vacuum swing adsorption (TVSA) cycles. In the first part, a novel way of describing the adsorption of \({\hbox {CO}}_{2}\) in presence of water vapor is proposed for co-adsorption kinetic and thermodynamic data gathered from the literature. Secondly, two TVSA cycle designs are proposed:

In this work a number of computational methods have been applied to study the adsorption of dimethylmercury (DMM) on the (ZnO)6 cluster and the influences of the supports (MgO, SBA-15) and external ions (Cl−, OH−) on the adsorption process: the energy and electronic properties were calculated using Geometry, Frequency, Noncovalent, eXtended Tight Binding method; global minimum was found by using the