Adsorption最新文献

Krypton is scarce, costly, and periodically experiences supply shortages, motivating the search for alternative probe molecules. Methane, which shares many physicochemical properties with krypton—such as kinetic diameter, polarizability, boiling point, and a lack of quadrupole moment—presents itself as a promising and more accessible surrogate. This study addresses whether methane can be used as a substitute for krypton for adsorption studies. Here, we demonstrate that across several representative adsorbents—including activated carbon, a zeolite, and flexible as well as rigid metal-organic frameworks—the adsorption-desorption isotherms of methane and krypton are remarkably similar in both shape and magnitude over a wide range of conditions. Comparative analysis reveals that differences in maximum adsorption capacities and affinity parameters between methane and krypton are minor, generally within experimental uncertainty, and that the qualitative adsorption mechanisms—including phase transitions in flexible MOFs—are consistently captured by both probes. To the best of our knowledge at the exception of H₂ isotopes, we show for the first time that same adsorption capacity data can be obtained with two different adsorbates.

The confining pressure of overlying strata can seriously affect the adsorption behavior of shale on CH₄ and CO₂. To address this issue, the Isothermal adsorption experiments of CH₄ and CO₂ on shale were conducted under unstressed (powdered sample, 0 MPa) and stressed (cylindrical sample, 21 MPa) conditions, and the micropore structure was characterized using scanning electron microscopy (SEM), low-temperature CO₂/N₂ adsorption, and nuclear magnetic resonance (NMR). Results indicate that the adsorption capacity of shale to CH₄ and CO₂ under stress is significantly lower than that under non-stress conditions, while the adsorption equilibrium time of shale to gas is longer than that under non-stress. In addition, the Dubinin-Radushkevich-Langmuir (DR-L) model was employed to describe the adsorption behavior of CH₄ and CO₂ in nanopores of different scales, and the fitting results reveal that the stress can lead to the existence of gas molecules in shale more inclined to exist in the form of micropore filling. Especially, the adsorption capacity difference between powdered and cylindrical shales a non-monotonic trend with a peak near the critical pressure, attributed to the progressive reopening of compressed adsorption sites as effective stress diminishes and to enhanced supercritical gas diffusivity. This study provides theoretical support for efficient shale gas extraction and CO₂ geological storage.

Volatile organic compounds (VOCs) are key precursors of tropospheric ozone and secondary organic aerosols, emitted predominantly from industrial coating, printing, petrochemical, and fine chemical processes. Among end-of-pipe technologies, adsorption is widely adopted for low-concentration, high-volume exhaust because of its low cost and operational flexibility. Its performance, however, degrades severely under high humidity—a bottleneck not yet fully resolved at the mechanistic level. This review examines VOCs adsorption on activated carbons, molecular sieves, and metal-organic frameworks, arguing that high-humidity performance is governed more by hydrophilic surface site density and pore confinement than by specific surface area alone. Moisture-resistant modification strategies and a low-carbon regeneration route integrating low-grade industrial waste heat (60–120 °C) are critically evaluated. Three research directions—low-temperature desorption materials, waste-heat-integrated system design, and intelligent process control—are identified to define a pathway toward efficient, stable, and low-carbon VOCs adsorption under high-humidity industrial conditions.

While vacuum pressure swing adsorption (VPSA) is a well-established separation technology for carbon capture from flue gas, it retains significant potential for process optimization. In this study, we propose and evaluate an enhanced VPSA cycle using Zeolite 13X, operating between a pressure range of 0.05–1.15 bar, to improve the separation performance. A multi-bed VPSA simulation model was established, with its constitutive equations verified against experimental breakthrough results for a simulated flue gas (15%CO₂/85%N₂). Various process configurations were demonstrated and compared, followed by a parametric analysis to optimize the separation efficiency. We compared traditional reflux VPSA (TR-VPSA), in which reflux gas enters the bed during a separate step, with joint-reflux VPSA (JR-VPSA), in which reflux enters the feed gas stream. The two configurations achieved comparable CO₂ purity and recovery, indicating that separation performance is relatively insensitive to the timing of reflux introduction. However, the process performance is highly sensitive to the reflux ratio (ratio of reflux flow to feed flow) and pressure equalization (PE) parameters. Increasing the reflux ratio from 0 to 70% enhanced the CO₂ purity from 35.80% to 66.02%, albeit with a moderate decrease in recovery from 97.40% to 91.55%. With pressure equalization time extending from 0 to 30 s, the recovery decreased by 1.28%, the purity increased by 7.09%, and the energy consumption decreased by 22.2 kJ/kgCO₂. However, all performance indicators stabilized when the pressure equalization time exceeds 30s. At a fixed PE time of 20 s, we further compared five PE configurations: top-to-top, bottom-to-bottom, concurrent top-to-top and bottom-to-bottom, top-to-bottom cascade, and bottom-to-top reverse cascade. The cascade equalization strategy achieved the highest purity and lowest energy consumption, whereas the “top-to-top” configuration maximized the recovery. This work offers valuable guidance for designing efficient PSA cycles in carbon capture applications.

Al-based metal-organic frameworks (MOFs) are promising candidates for hydrogen storage. Recently, a set of Al-based MOF-521 materials has been reported. These materials have very similar geometries, but differ in their substituents; therefore, when compared with other MOFs, they can be used as a controlled reference set to identify the factors governing hydrogen physisorption. GCMC simulations of the storage capacities of these MOF-521 materials, MOFs with similar metal composition, pore size, density, and porosity, and current benchmark hydrogen storage MOFs were carried out at room temperature and pressures between 0.5 and 25 MPa. The results were then analyzed as functions of composition and structural and chemical factors. The comparative analysis suggests that, for the MOFs studied, the usable storage capacities are more strongly influenced by porosity and density than by the chemical environment and substituents considered in this study. The driving range of hydrogen vehicles using tanks that store gas by adsorption on the MOF-521s and the other MOFs has also been calculated. It was found that the usable volumetric capacities and the driving ranges of vehicles using MOF-521s were similar to those of vehicles using current benchmark MOFs at 15-20 MPa and room temperature.

Multicomponent adsorption equilibria strongly influence the performance of adsorption-based carbon dioxide separation processes. Ideal Adsorbed Solution Theory (IAST) provides a practical framework to predict competitive adsorption from pure-component isotherms, but its application in process simulation and optimization is often hindered by the high computational cost associated with implicit equilibrium calculations and numerical integration. This study develops a partial surrogate model that reproduces IAST predictions while substantially reducing computation time. The surrogate replaces only the equilibrium calculation rather than the full process model; it preserves the governing mass and energy balances and cycle operation, is straightforward to validate against equilibrium reference data, and can be reused across different process configurations and operating conditions with minimal reimplementation. A multilayer perceptron was trained using equilibrium data generated from IAST calculations based on fitted pure-component isotherms for the metal–organic framework UTSA-16. The surrogate model was successfully integrated into a two-bed temperature swing adsorption model, enabling dynamic process simulations that capture time-dependent competitive adsorption behavior. Finally, the surrogate-integrated temperature swing adsorption superstructure was optimized as a large-scale nonlinear programming problem.

Tectonic deformation strongly modifies the molecular structure and adsorption-energy heterogeneity of coal, yet its influence on CH₄ and O₂ competitive adsorption and molecular transport remains insufficiently understood. In this study, elemental analysis, X-ray diffraction, Fourier-transform infrared spectroscopy, and solid-state ¹³C nuclear magnetic resonance were used to constrain representative molecular models of primary coal and tectonically deformed coal from Pingmei No. 10 Mine. Grand canonical Monte Carlo and molecular dynamics simulations were subsequently conducted to investigate model-derived pore accessibility, single-component adsorption, CH₄-O₂ competitive adsorption, adsorption energetics, and self-diffusion behavior. The representative tectonically deformed coal model exhibited a larger probe-accessible free volume and probe-accessible surface area than the primary-coal model. At 293 K and 10 MPa, the simulated CH₄ uptake of tectonically deformed coal was 2.01 mmol·g^-1, approximately 51.13% higher than that of primary coal. The simulation-derived apparent isosteric heat of CH₄ decreased with increasing loading, whereas O₂ in tectonically deformed coal exhibited a non-monotonic trend, indicating a potentially broader adsorption-energy distribution. Under an equimolar CH₄ and O₂ reservoir composition, the simulations predicted preferential CH₄ adsorption. The MD-derived self-diffusion results further indicated different pressure-dependent responses in the two representative coal models. These findings provide a simulation-based molecular interpretation of deformation-induced changes in gas adsorption and transport, subject to the assumptions of the selected coal structures and force field.

The adsorption behavior of vanadium onto the ion-exchange resin Purolite D3411 was investigated over a wide pH range (2.0–7.5) and in the presence of competitive anions (Cl(^-) and SO(_4^{2-}), 0–1000 mg L(^{-1})). Due to the hydrated nature of the polymeric resin beads, adsorption capacity is expressed on a volumetric basis (mg L(^{-1})), representing an apparent sorption capacity under experimental conditions. Batch experiments revealed a strong dependence of adsorption equilibrium on pH, with a maximum removal efficiency of 78% observed at pH=5.0. Equilibrium data were well described by the Langmuir isotherm model, with a maximum calculated sorption capacity of 90 909 mg L(^{-1}). Adsorption kinetics were evaluated using pseudo-first-order (PFO), pseudo-second-order (PSO), and intra-particle diffusion (IPD) models. At pH=4.5, both PSO and IPD models adequately described the data, indicating contributions of surface adsorption and intra-particle diffusion. At pH=6.0, the PSO model provided the best fit, suggesting that surface reaction kinetics is the rate-limiting step under these conditions. Dynamic column experiments further confirmed the significant effect of solution pH on adsorption performance. Breakthrough curves showed consistently higher adsorption capacities at pH=4.5 compared to pH=6.0 regardless of feed composition. The best performance was obtained at low concentrations of competitive ions (50 and 100 mg L(^{-1}) Cl(^-) and SO(_4^{2-})). Under these conditions, the breakthrough capacity at pH=4.5 reached approximately 50 000 mg L(^{-1}). These results demonstrate that Purolite D3411 exhibits favorable adsorption properties for vanadium removal under mildly acidic conditions, with adsorption governed by pH-dependent equilibrium, kinetic limitations, and competitive ion effects typical for ion-exchange systems in aqueous environments.

In this work, the capacity of the IRMOF-1 was evaluated, for separation of H₂S from gas mixture with the objective of gas sweetening. The grand canonical Monte Carlo simulation (GCMC) was performed in order to simulate adsorption of pure methane, pure H₂S and their binary mixtures. The simulations were performed in the conditions close to the real natural gas composition at temperature of 298 K at different pressures to clarify how operating conditions govern the loading behavior. For the adsorption of pure H₂S in the IRMOF-1, three force fields were examined and the candidate force-field was selected. Furthermore, effect of temperature on the adsorption of pure H₂S was examined by GCMC with conducting simulation at 320 K and 298 K. We have validated simulation results for pure gaseous states against experimental values and good agreements between experimental values and simulated values were observed. For the mixture simulation, further validations were performed by comparing the results with previously published studies, confirming physical consistency in the adsorption isotherms and selectivity trends. Structural investigation by analysis of Radial Distribution Functions (RDFs) and coordination numbers shows that ZnO nodes in IRMOF-1 are preferred sites for H₂S adsorption both in pure and mixture states. For the gaseous mixtures of H₂S and CH₄, the results indicated that IRMOF-1 has high capacity for adsorption and separation of H₂S. It was observed that IRMOF-1 has an excellent selectivity of H₂S over CH₄. This behavior originates from strong electrostatic and van der Waals interactions between H₂S molecules and the framework, which dominate over the weaker interactions with CH₄. Additionally, a brief evaluation of the heat of adsorptions indicates the thermodynamic driving force for H₂S uptake.