Adsorption最新文献

The prediction of adsorption in carbonaceous materials via molecular simulation is a challenging task. Unlike zeolites and MOFs, carbons are amorphous. Homogeneous activated carbon models are commonly used for characterization. Here, we demonstrate that, despite their relative success, homogeneous models are inadequate for predicting the adsorption of SO₂, a contaminant in flue gases that interferes with CO₂ capture processes. To address this issue properly, we have developed a new set of SO₂ isotherms based on a heterogeneous reactive model (rMD). The isotherms were calculated using the Monte Carlo method in the grand canonical ensemble. Two samples of commercial carbons, C141 and WV1050, had their SO₂ adsorption capacities predicted by combining the regular N₂ at 77 K and CO₂ at 273 K characterization with the new set of SO₂ isotherms in the rMD model. By incorporating the heterogeneous model in the characterization process, we have considerably improved the agreement between experimental and simulated isotherms for both carbons. The use of the rMD heterogeneous kernel will enable new adsorption predictions for adsorbates where previous homogeneous models have failed.

The decomposition of NO dimers on metal surfaces is a critical step in nitrogen oxide reduction technologies. In this study, we investigate the Cu(100) surface as a catalytic platform for this reaction using ab initio molecular dynamics (AIMD) simulations, based on density functional theory (DFT) with van der Waals corrections. A detailed analysis of the energy partitioning in the desorbed (hbox {N}_2hbox {O}) molecule reveals that the activation energy associated with N–O bond cleavage is primarily redistributed into the rotational mode, followed by the translational mode, and small fraction of the energy is transferred into vibrational excitation and dissipated into surface modes. This mode-specific energy redistribution suggests that enhancing the excitation of the rotational degree of freedom could improve the rate and efficiency of NO reduction. In addition, we evaluate the adsorption behavior of the reaction products, (hbox {N}_2hbox {O}) and atomic O, on Cu(100) using DFT calculations. (hbox {N}_2hbox {O}) is found to preferentially adopt a bent chemisorbed geometry, while atomic O favors adsorption at the fourfold hollow site. These stable configurations serve as the final state for the NO dimer decomposition pathway. While for the initial state is flat-ONNO dimer, which was discussed comprehensively in our previous work. Together, these results offer fundamental insights into the desorption dynamics, energy transfer mechanisms, and product–surface interactions that govern NO decomposition on copper catalysts, and may inform the rational design of more effective, non-PGM catalytic systems for environmental applications.

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Water adsorption on Aluminium Fumarate (Al-Fum), a promising MOF for low-temperature heat-driven applications, exhibits complex isotherm shapes that challenge conventional modeling approaches. In this work, we develop a physically grounded dual-site adsorption model that combines Langmuir adsorption on high-energy sites with cooperative water clustering based on association theory. The model reproduces full isotherm profiles across a broad temperature range (20–90 °C) using eight temperature-independent parameters with clear physical significance. The model achieves excellent agreement (adjusted R² = 0.9957), accurately capturing both low-pressure concavity and the S-shaped transition. It also enables the calculation of isosteres and isosteric heats of adsorption, revealing distinct thermodynamic regimes governed by the two adsorption mechanisms. To demonstrate system-level relevance, the model is applied to a typical intermittent adsorption cooling cycle operating at 10/30/60°C. Al-Fum delivers a thermal COP of 0.785 (excluding heat exchangers’ sensible heat) and a cycled mass of 177.5 g kg⁻¹, outperforming benchmark materials. This work provides a robust, physically sound modeling tool for the design and optimization of advanced adsorption-based thermal systems.

Many studies that use an automated sorption balance to determine a water vapor sorption isotherm for wood collect data until the moisture content change is less than or equal to 0.002% min⁻¹ (20 µg g⁻¹ min⁻¹). This stop criterion has been claimed to give errors in equilibrium moisture content (EMC) predictions of less than 0.001 g g⁻¹ but over the past 10 years, studies have shown that the actual errors can be greater than 0.01 g g⁻¹ because the measurements are stopped well before equilibrium is reached. Despite the large errors associated with this stop criterion, it remains popular due to the speed at which isotherms can be measured. This paper utilizes data from a worldwide interlaboratory study on automated sorption balances to develop a correction method for estimating EMC of western larch (Larix occidentalis Nutt.) from the moisture content corresponding to the 20 µg g⁻¹ min⁻¹ criterion. The study uses data from 72 relative humidity absorption steps with hold times of 7–10 days from 21 different laboratories and eight different instrument models. EMC is defined based on the inherent mass stability of automated sorption balances determined in the first part of this interlaboratory study. On average the sorption process is less than 80% complete when the 20 µg g⁻¹ min⁻¹ criterion is reached, resulting in a mean absolute error (MAE) of 0.006 g g⁻¹. The correction equation for estimating EMC reduces the MAE to 0.001 g g⁻¹. The analysis presented in this paper, along with the correction equation, can be considered for certain use cases to reduce systematic errors and shorten measurement times.

Using the Lattice Boltzmann method (LBM) for simulation of fluid dynamics in complex systems such as adsorption with the advection terms of scalar fields (concentration and temperature distribution), different approaches of advection coupling to the fluid motion can be proposed: “Active or Passive Scalers”. In the present study, the usefulness of active or passive scalars in simulation of an adsorption bed using LBM at different operating conditions such as temperature, pressure and feed flow rate were investigated. In the active scalar approach in LBM, the collision operator in the Boltzmann transport equation consists of two terms: the self and cross collision. On the other hand, the collision term for a passive scalar comes from the Chapman relationship. As the cross collision term in active scalar has an inverse relationship with diffusion coefficient, the effect of this term reduces in gas systems such as adsorption with a high diffusion coefficient; thus, the active and passive approaches become similar. It is obvious that in systems with a lower diffusion coefficient (liquid systems), the cross collision term in collision operator in LBM is high; therefore, it is expected that the active approach with more precise results deviates from the passive approach. Results showed that in most cases, the average relative error compared to experimental data was less in active scalar than in passive scalar approach, indicating that the active scalar approach predicts the adsorption behavior with higher accuracy in comparison with the passive approach.

Nowadays, many pollutants, especially polycyclic-aromatic-hydrocarbons (PAHs), are a high threat to humans as well as animals due to their carcinogenic behaviour. Therefore, in the present research work, we studied the adsorption behaviour of three different PAHs, namely anthracene, benzo[a]pyrene, and chrysene, on monolayer beta phosphorous nitride nanosheet (β-PN-sheet) using the density-functional-theory (DFT) method. Besides, low-dimensional material possesses many features, including a large active surface region and the electronic properties can be fine-tuned easily, which are the main requirements for chemical sensors. Initially, the structural stability of the β-PN-sheet is confirmed with the support of phonon-band-maps and formation energy. Furthermore, the electronic properties of β-PN-sheet are investigated using band maps and projected-density-of-states (PDOS) maps. We also studied the influence of compressive strain on the electronic properties as well as on the adsorption properties of the β-PN-sheet. The computed band gap of β-PN-sheet slightly increases from 3.355 eV to 3.537 eV owing to the compressive strain. The adsorption behaviour of PAH pollutants on β-PN-sheet is studied with significant factors, namely adsorption energy, relative band gap changes, and Mulliken population analysis. Furthermore, the adsorption of PAHs on β-PN-sheet gets slightly improved with applied compressive strain, and the adsorption energy falls in the scale of physisorption (−0.292 eV to −0.404 eV). Furthermore, a fast recovery time is obtained while desorbing PAH pollutants from the β-PN-sheet. The sensing response of β-PN-sheet to PAHs gets enhanced by applying compressive strain.

The selective capture of volatile organic compounds (VOCs) is a significant challenge in environmental remediation. In this study, we explore how MOF structural flexibility and the electronic properties of VOCs influence their adsorption by comparing two functionalized zeolitic imidazolate frameworks: the flexible ZIF-8_CH₃ and the rigid ZIF-8_Br. Using benzene and hexafluorobenzene as probe molecules with contrasting quadrupole moments, we demonstrate that ligand functionalization significantly impacts both structural dynamics and adsorption/separation performance. ZIF-8_CH₃ exhibits higher overall uptake capacities, reaching up to 7.3 mmol/g for hexafluorobenzene. In contrast, ZIF-8_Br shows superior separation capabilities, with IAST selectivity values reaching 17.1 for benzene/hexafluorobenzene mixtures at low pressures. Our experimental and computational analyses reveal that aromatics with negative quadrupole moments more readily appear to trigger the gate-opening phenomenon, establishing a potential correlation direct correlation between electron density distribution and molecular sieving efficiency. These findings offer new insights into the rational design of functionalized frameworks for selective VOC capture, highlighting the crucial role of electronic effects in determining host-guest interactions and separation performance.

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In this study, the adsorption and sensing capabilities of the recently introduced B₂C₃N nanosheet toward several typical hazardous heavy metals including Cu (0), Cu (I), Cu (II), As (0), As (III), and V (0) were systematically investigated using density functional theory (DFT) at the B3LYP/6-311G(d, p) level. The optimized geometries, adsorption energies, electrical conductivities, and recovery times were thoroughly analyzed to evaluate the selectivity and stability of the nanosheet-metal complexes. Our results reveal that B₂C₃N exhibits strong and selective adsorption toward Cu (II) and As (III) species, with significant changes in electrical conductivity serving as reliable sensing signals. The calculated recovery times indicate practical potential for reusability and efficient desorption of certain metals. This computational insight provides a theoretical foundation for the application of B₂C₃N nanosheets in environmental remediation and heavy metal sensing. Limitations of the current gas-phase model and suggestions for future experimental validation and extended theoretical studies are also discussed to guide further research.

Fast pressure swing adsorption (FPSA) is an adsorption-based separation process with cycle durations ranging from a few to tens of seconds. While widely used in small-scale oxygen generators, FPSA still holds significant potential for improvement. In this study, we propose and demonstrate a novel rapid vacuum swing adsorption (FVSA) cycle, where adsorption occurs at atmospheric pressure and desorption under vacuum, to enhance small-scale oxygen production from air. A simulated air mixture, containing 78% nitrogen (N₂), 21% oxygen (O₂) and 1% argon (Ar), was processed through a dual-column FVSA system using LiLSX zeolite as the adsorbent. A numerical model was developed on Aspen Adsorption and validated against previously reported results. A parametric study was conducted to assess the effects of various operating conditions on separation performance. The results indicate that a low feed flow rate, low desorption pressure, and an optimal length-to-diameter (L/D) ratio improve the separation efficiency. Under operating conditions of 101.1 kPa adsorption pressure, 40.3 kPa desorption pressure, and a feed rate of 47 L/min, the system achieved a 91% O₂ product stream with a 5 L/min flowrate and 44% O₂ recovery. Compared to traditional FPSA, FVSA reduced energy consumption by 13% (39.24 vs. 33.99 kJ·mol⁻¹O₂) and lowered the air-to-oxygen ratio by 25% (14.4 vs. 10.8) while maintaining comparable O₂ purity, demonstrating its potential for more efficient oxygen production.

This study reports an anionic metal-organic framework (iMOF-A), {(H₂pa)₃[Co₃(BTCA)₃].6H₂O}_n, where H₂pa. is 1,3-propylenediamonium and BTCA is 1,2,3,4-butanetetracarboxylate. The compound, based on Co²⁺, crystallizes in a monoclinic system, (space group I2/a) with a non-interpenetrated three-dimensional pts topology. Its charge balancing is achieved by H₂pa cations located in the framework’s pores, which can be exchanged with Ni²⁺ ions. The compound was characterized by single-crystal and powder X-ray diffraction, infrared spectroscopy, elemental analysis, thermogravimetric analysis, and ultraviolet-visible absorption spectroscopy. The ion-exchange properties were evaluated by substituting the propanediammonium cations with Ni²⁺ from aqueous solution. Batch experiments assessed the framework’s effectiveness in selectively adsorbing Ni²⁺, considering variables like initial metal ion concentration and contact time. The results show a high affinity for Ni²⁺ ions, attributed to the unique polymer’s structural features. This work expands the library of anionic metal-organic frameworks and provides insights into the tunable ion-exchange properties of such frameworks.

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A new metal-organic framework {(H₂pa)₃[Co₃(BTCA)₃].6H₂O}_n exhibits ion exchange between pore diammonium cations and hard metals in aqueous solution, supported by structural and spectroscopic studies.