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
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 ^-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.
This paper reports the results of an international interlaboratory study sponsored by the Versailles Project on Advanced Materials and Standards (VAMAS) and led by the National Institute of Standards and Technology (NIST) on the measurement of low-pressure CO2 adsorption isotherms at 25 °C on zeolite 13X (NIST research grade test material 10257). Eighteen laboratories participated in the study and contributed 21 datasets. From these data, a consensus reference isotherm, along with the 95
The growing demand for efficient and sustainable thermal management technologies has intensified research on adsorption-based refrigeration systems. In this study, CO2 adsorption on two highly microporous activated carbons, Maxsorb III and ACF-A20, is investigated using a grand canonical statistical physics (GCSP) framework to provide a detailed thermodynamic and energetic description of the process. The monolayer model with a single effective energy provides an excellent representation of the experimental isotherms and allows the determination of key physicochemical parameters, including site occupancy, density of accessible adsorption sites, saturation capacity, and adsorption energy. The results indicate that CO2 adsorption is predominantly governed by physisorption within confined porous structures. The temperature dependence of the model parameters shows a systematic decrease in site occupancy, accompanied by enhanced site accessibility and reduced saturation capacity, reflecting the combined influence of thermal agitation and confinement effects. Based on the derived adsorption framework, thermodynamic functions such as internal energy, enthalpy, and Helmholtz free energy are evaluated as functions of pressure and temperature, confirming the spontaneous and exothermic nature of the adsorption process and its relevance for thermal energy storage and conversion applications. Furthermore, these thermodynamic insights are applied to assess the performance of two adsorption refrigeration cycle configurations. At 363 K, the predicted coefficients of performance (COP) are 0.59 and 0.89 for cycle I, and 0.79 and 0.64 for cycle II, for Maxsorb III and ACF-A20, respectively. Overall, this work highlights the capability of statistical physics modeling to bridge microscopic adsorption mechanisms with macroscopic thermal system performance, providing useful guidelines for the design and optimization of advanced adsorption cooling systems.
The applicability of the environmentally friendly MIL-100(Fe) metal-organic framework is explored for the recovery of unreacted monomers from nitrogen-rich vent streams generated in the two highest-volume thermoplastics industries: polyethylene and polypropylene. Adsorption equilibrium isotherms for ethylene and propylene were measured at multiple temperatures and fitted using the Langmuir model. Breakthrough experiments were conducted for ethylene/nitrogen and propylene/nitrogen mixtures using a bench-scale fixed-bed unit. Simulations using a dynamic fixed-bed model accurately reproduced the experimental data, validating both the kinetic and multicomponent equilibrium behavior of the system. Industrial-scale Pressure Swing Adsorption (PSA) and Multitubular Temperature and Pressure-Swing Adsorption (MT-TPSA) separation systems were designed, and evaluated. For ethylene recovery, a three-column PSA cycle operating between 0.3 and 9 bar at 343 K is recommended. This system achieved a productivity of 2.23 mol/(kg·h) and a recovery capacity of 21.0 kg C₂H₄/(m³·h) with a total energy consumption of 10.13 MJ/kgC2H4. For propylene recovery, both a PSA cycle (0.3–8 bar, 343 K) and a MT-TPSA cycle (1–5 bar, 303–393 K) are considered. The MT-TPSA process offered higher productivity (6.72 mol/(kg·h)) and recovery capacity (38.9 kg C₃H₆/(m³·h)), though at a higher total energy cost of 7.46 MJ/kg C₃H₆ compared to 4.37 MJ/kg C₃H₆ for PSA, with a productivity of 1.48 mol/(kg·h) and recovery capacity of 21.03 kg C₃H₆/(m³·h).
ETS-4 titanosilicate adsorbent with unique characteristics is very suitable for CO2 adsorption. However, it is still necessary to study the adsorption performance details and regeneration performance of this adsorbent as well as its ion-exchange type Sr-ETS-4 and the effect of the activation temperature for CO2/CH4 separation and post-combustion CO2 capture (CO2/N2 separation). In the present work, CO2, CH4, and N2 adsorption equilibria for the synthesized ETS-4 and Sr-exchanged ETS-4 were measured at 25 °C. Adsorption data were used for modeling to predict the phase diagram, selectivity, and total adsorption of samples in binary mixtures with the IAST method. Also, the CO2 adsorption kinetics data were measured and investigated by micropore diffusion and Pseudo-nth-Order (PNO) models. The results showed that ion exchange with strontium enhanced significantly the thermal stability of ETS-4. Also, although the CO2 adsorption capacity on SrETS-4-110 decreased by less than 35
The recovery and upgrading of low-grade thermal energy has become an important challenge for improving industrial energy efficiency. Adsorption heat transformers (AdsHT) provide a viable solution by converting waste heat into higher-temperature heat streams exceeding 120 °C through reversible adsorption–desorption cycles. In this study, the thermodynamic performance of an AdsHT system was assessed using two post-synthetically modified MOF-808 materials, MOF-808NDS and MOF-808PDS, as adsorbents for water vapor. A statistical physics approach based on the grand canonical ensemble was applied to investigate the adsorption mechanism and to determine the key energetic and structural parameters governing the process. The modeling results reveal that water adsorption on both materials can be described by a monolayer model involving two distinct adsorption energy levels. Stereographic analysis suggests that water molecules interact with the adsorption sites mainly in a non-parallel orientation. The calculated adsorption energies, lower than 40 kJ mol⁻¹, indicate that the process is dominated by weak physical interactions such as hydrogen bonding and van der Waals forces. Furthermore, pore size distribution analysis confirms the microporous structure of the studied frameworks. The thermodynamic analysis of the adsorption cycle shows coefficients of performance (COPGCSP) of 0.764 for MOF-808NDS and 0.826 for MOF-808PDS, highlighting the superior efficiency of MOF-808PDS due to its higher water uptake and favorable pore characteristics. These findings demonstrate that functionalized MOF-808 materials are promising candidates for enhancing the performance of adsorption heat transformer systems dedicated to sustainable thermal energy utilization.
MUF-16 (MUF = Massey University framework) is currently being commercialized for carbon dioxide capture from large-scale industrial emissions and for biogas upgrading. Although comprehensive experimental and pilot-trial data have already confirmed MUF-16’s structural stability towards impurity gases, such as NOx, H2S, and CO, quantitative thermodynamic data regarding the uptake of these components have not yet been reported. Experimental limitations associated with toxic and corrosive gases make laboratory measurements difficult and underscore the importance of developing reliable simulation techniques to predict their influence on CO2 capture by MUF-16. Here, we employed the RASPA simulation package to predict the adsorption isotherms of such gases. The results demonstrate that MUF-16 maintains its strong affinity for CO2 in the presence when these gases are present in the gas stream. These results strengthen the commercial potential of MUF-16 for carbon capture across a diverse range of industrial scenarios.
The urgent need to mitigate anthropogenic CO2 emissions has driven the advancement of various carbon capture technologies, with solid adsorbents emerging as a key focus. Among them, activated carbons (ACs) are particularly attractive due to their excellent adsorption capacity, thermal stability, and cost-effectiveness, making them well-suited for industrial-scale applications. However, achieving high CO2 selectivity in biomass-derived ACs remains a significant challenge, requiring precise control over pore structure and surface functionality. In this study, nanoporous ACs were synthesized from palm leaves using phosphoric acid (H3PO4), potassium hydroxide (KOH), and sodium bicarbonate (NaHCO3) as activating agents, achieving optimized pore sizes (< 2 nm). Different Characterization techniques were employed to assess the properties of the prepared ACs. Morphological analysis results indicate that the AC-P-H3PO4 exhibits a honeycomb structure with abundant pores, enabling CO2 capture (up to 1.42 mmol/g) with a selectivity of up to 44.3, surpassing other reported ACs. Isosteric heat of adsorption (Qst values = 22–27 kJ/mol) measurements demonstrate that CO2 adsorption occurs primarily via physisorption, suggesting lower energy requirements for regeneration. Additionally, performance indicators for a cyclic vacuum swing adsorption (VSA) process were evaluated, highlighting the practical suitability of these nanoporous ACs for CO2 capture applications. ACs exhibited a CO2 working capacity of up to 0.97 mmol/g and regenerability of up to 81
Adsorption calorimetry has been used to provide a novel characterisation of the adsorption of carbon dioxide within clay-rich carbonate mudstones from the Aphrodite Mediterranean gas field, particularly considering the distribution of strength of adsorption sites, and their external accessibility via mass transfer measurements. The distribution of heat of adsorption (HoA) with coverage, determined for carbon dioxide via adsorption calorimetry, was found to have a subsidiary peak at intermediate coverage values for all rock types considered. A comparison of the carbon dioxide and nitrogen isotherms led to the proposed origin of the peaks lying with a particular surface disposition of adsorbate, and this mechanism was found to be predictive of the position of the peaks. Coupled kinetic gas uptake and calorimetry experiments revealed the relative external accessibility of sites with differing HoA. For some rocks the accessibility was similar for all adsorption sites, but for one rock type the accessibility was best for sites with the highest HoA. This difference was found to be associated with the particular pathways available to the various adsorption sites, as detected by serial nitrogen and iodononane experiments.
This work presents a comprehensive experimental and modelling study of the adsorption and desorption behavior of volatile fatty acids (VFA) under well-controlled conditions, with the aim of developing an integrated modelling framework with experimental data (adsorption equilibrium and dynamic behavior) for better predictions of process performance. Batch experiments using single-component solutions were first performed to determine adsorption equilibrium and to identify a suitable adsorbent for VFA separation. The nonfunctionalized adsorbent (Amberlite XAD-4) was selected and used in the fixed-bed experiments, to determine single- and multicomponent breakthrough curves. In a multicomponent system, adsorption capacities ranged from 0.125 mmol·gads−1 for acetic acid to 1.564 mmol·gads−1 for hexanoic acid, highlighting significant differences in affinity among VFA. During these assays, some swelling of the adsorbent was observed with increase adsorbed quantity in the solid phase. A mathematical model was developed combining the dual-site Langmuir model and the Linear Driving Force model to describe adsorption equilibrium and intraparticle diffusion, respectively. Adsorbent swelling was incorporated by defining the mass transfer coefficient dependent on the average adsorbed quantity in the solid phase, enabling the model to capture swelling-induced variations in transport properties. The proposed model successfully described VFA adsorption and desorption behavior with single- and multicomponent solutions, and in both batch and fixed-bed systems. This work provides a consistent experimental-modelling methodology for VFA adsorption and represents a first step toward the development of intensified separation processes such as simulated moving bed systems and the future application to real effluents.
The present study investigated the equilibrium and kinetics of nitric oxide (NO) and nitrous oxide (N2O) adsorption at different temperatures on natural erionite from Agua Prieta, Sonora, Mexico (ZAPS), modified by ion exchange with Fe2+, Co2+, and Cu2+. UV–Vis diffuse reflectance, energy dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), and Mössbauer spectroscopy were used to characterize the exchanged samples. The Freundlich, Langmuir, and Brunauer–Emmett–Teller (BET) models were employed to analyze the adsorption data. The isotherms of N2O and NO adsorption in the exchanged samples at the same temperature and at low equilibrium pressures showed that the adsorbed amount and irreversibility grade decrease in the order: ZAPS-Co > ZAPS-Fe > ZAPS-Cu, which was attributed to the increasing acidity of the cations. At high equilibrium pressures, the NO adsorption capacity changed in order due to the increased pore volume resulting from the exchange of smaller cations. At equilibrium, the ZAPS-Fe and ZAPS-Cu samples exhibited the best performance for separating NO/N2O mixtures at high temperatures and low concentrations, whereas for high concentrations, the ZAPS-Cu sample was the most effective for separation This result indicated that upon contact with the ZAPS-Cu catalyst, the NO/N2O mixture undergoes selective adsorption of NO, resulting in an increase in the relative concentration of N2O in the gas phase. Under non-equilibrium conditions at low temperatures, for the separation of N2O-NO mixtures, the N2O was adsorbed more rapidly than NO.
Scaling passive direct air capture (DAC) with moisture swing sorbents requires an understanding of how ambient meteorological conditions constrain achievable performance. While laboratory and device-scale models of moisture swing adsorption exist, there is currently a lack of parsimonious frameworks that translate long-term weather variability into site-level productivity and water-loss metrics for screening and deployment decisions. In this study, we develop a reduced-order, meteorology-driven process model for a moisture swing passive DAC system that maps ambient temperature, relative humidity, and wind speed directly to CO2 productivity and net water loss. The model employs decoupled proxy equilibria, a modified Langmuir isotherm for CO2 loading and a Flory–Huggins model for H2O loading, closed with linear-driving-force kinetics parameterized by ambient wind speed and temperature. Using 17 years of NOAA weather data for St. Johns, Arizona, we quantify climatological seasonal variability and the impact of interannual weather fluctuations. Results show that relative humidity is the dominant driver of both CO2 productivity and water loss. Low-humidity conditions enable higher productivity at the cost of increased net water loss, whereas periods of sustained high ambient humidity can preclude capture entirely. Notably, we identify distinct wintertime intervals during which the equilibrium CO₂ loading under ambient conditions falls below the regenerated state, resulting in zero net capture despite continued cycling. This finding highlights a minimum required swing capacity and establishes a fundamental climatic constraint on passive DAC operability. By explicitly linking meteorology to CO2 productivity and water loss, this work provides a screening-level framework for geospatial site triage and operational planning of moisture-swing passive DAC systems, with results interpreted as bounded performance estimates rather than device-specific predictions.
Natural gas, an essential energy source, often contains undesirable acidic components such as hydrogen sulfide (H2S) and carbon dioxide (CO2), which must be removed to prevent corrosion, environmental pollution, and efficiency loss. During the dehydration of acid gases, the formation of carbonyl sulfide (COS) and elemental sulfur poses significant operational challenges, particularly in temperature swing adsorption (TSA) units using molecular sieves. Although COS is initially non-corrosive, it can hydrolyze to form H2S and CO2, exacerbating corrosion and reducing process reliability. In this study, molecular simulations using the RASPA (Version 2) code were employed to investigate the adsorption behavior of H2O, H2S, and CO2, and to explore the reaction pathways leading to COS and elemental sulfur formation in Na-LTA4A zeolite. The Langmuir–Freundlich model was applied to describe the adsorption isotherms, while the Aspen Adsorption (Version 12.1) software was used to simulate the TSA process under various operational conditions. Simulation results reveal that Na-LTA4A enhances H2S conversion to COS up to 81
Algérie Télécom is a joint-stock company in the telecommunications networks and services sector. To protect its equipment from extreme weather, the company deploys Shelters globally, shielding the equipment from harsh climate conditions. However, these structures face challenges in dissipating internal heat generated by active equipment, especially in desert regions where summer temperatures in the shade exceed 45 °C. Maintaining an internal temperature below 35 °C is crucial for ensuring the proper functioning of the equipment. This study examines a more efficient solution based on solar-powered adsorption cooling using the AC35 activated carbon-methanol pair, backed by a developed thermodynamic model and a numerical simulation algorithm to analyze the system’s behavior. The results show that, over an ambient temperature range of 15 °C to 45 °C and heat dissipation from 1.5 kW to 8.5 kW, the thermal power exchanged by the desorber varies from 5.52 kW to 382.5 kW, while that of the condenser ranges from 3 to 200 kW. Additionally, the mass flow rate of the refrigerant fluid increases proportionally with the heat absorbed by the desorber, rising from 2.58 g/s to 175.62 g/s. Economically, adopting adsorption cooling would reduce total energy investment costs by 48.3
The vacancy solution theory is one of the approaches used to describe adsorbed phase non-ideality that leads to a flexible pure component isotherm and allows to predict or correlate multicomponent adsorption equilibrium. This contribution identifies the correct reference state and presents a new derivation of the theory applicable with any activity coefficient model. The definition of the reference state and the derivation identify clearly the requirement for thermodynamic consistency, which as for any model that reduces to the Langmuir multicomponent isotherm is that the saturation capacities of all components must be the same. A numerical example based on the thermodynamically consistent dual site Langmuir model for a hypothetical mixture that has an azeotrope is used to discuss the coupling of the non-random two liquid model with the vacancy solution theory and test its predictive ability.
Non-monotonous trends in the Henry adsorption coefficient with respect to carbon number during the adsorption of n-alkanes are often categorized under the term “cage effects”. Recent experimental studies have shown that such effects emerge for a variety of cage-type CHA and AEI zeolite structures. Furthermore, observations of unusual kinetic effects (“window effects”) have been linked to this cage effect but remain controversial. Still, cage and window effects have been proposed to be generic for structures containing larger features (cages), separated by narrow openings. In this work, we present a simple 1D model based on rectangular free energy profiles for the individual CHx beads that compose the n-alkane chain. The descriptive model offers a prediction of both Henry and diffusion coefficient trends. Using the model, recent observations can be rationalized from the perspective of adsorption in larger cages and narrow openings. It is shown that the local minimum in Henry coefficient coincides with a local maximum in diffusion coefficient. Although the model does not account for even more complex adsorption mechanisms such as molecular coiling within cages, it demonstrates how such unusual effects can be predicted using only straightforward assumptions.
