Isosteric Heat Of Adsorption Research Articles

Adsorption of selected GHG on metal-organic frameworks in the context of accompanying thermal effects

Thermal effects accompanying gas sorption on micro- and mesoporous materials provide unique insights into the type, course, and efficiency of sorption. In this study, metal-organic frameworks (MOFs) with different topologies and chemical structures were synthesized and investigated: HKUST-1, Ni-MOF-74, UiO-66, and MIL-140A. These MOFs were characterized structurally and sorptively with respect to selected greenhouse gases (GHGs). Sorption capacities for CO2 and CH4 were determined at several temperatures and measurement pressures, and the maximum sorption capacity was determined using the Langmuir-Freundlich model. Thermal effects accompanying adsorption were quantified through the isosteric heat of adsorption parameter. For each MOF, the values of isosteric heat of adsorption were higher for CO2 than for CH4. The values of this parameter was determined in the following order: HKUST-1 > Ni-MOF-74 > UiO-66 > MIL-140A. Energy homogeneity of the adsorbent surface was observed in nearly all cases, except for UiO-66 during CO2 adsorption. Changes in the determined isosteric heat of adsorption of CO2 with increasing sorption capacity were in the range of 5-15 kJ/mol, while for CH4 they ranged from 1.4 to 17 kJ/mol, respectively. The level of thermal selectivity of CO2 over CH4 was determined in the following order: UiO-66 (1.9) > Ni-MOF-64 (1.7) > MIL-140A (1.5) > HKUST-1 (1.1).

Screening of metal–organic frameworks for efficient electrocatalytic nitrogen reduction

AbstractIn this work, 44 metal–organic frameworks (MOFs) are screened for efficient electrocatalytic nitrogen reduction reaction (eNRR). The isosteric heats of N2 adsorption on the 44 metal active centers of MOFs are calculated by the grand canonical Monte Carlo method. It is found that p‐block‐elements exhibit the highest N2 affinity among all screened elements, implying their excellent catalytic potentials for eNRR. Furthermore, the Al element is preferentially chosen as the metal center of MOFs (MIL‐53 (Al)) owing to its relatively low toxicity and cost. Combined in situ Diffuse Reflectance Infrared Fourier Transform (DRIFT) analysis with theoretical calculation, we found that N2 is mainly attracted by the bridging oxygen of Al‐O‐Al structure in the MIL‐53 (Al). The optimized MIL‐53 (Al) shows a superior activity with the NH3 yield rate of 74.55 ± 1 μg h−1 mgcat−1 at −0.3 V vs. Reversible Hydrogen Electrode (RHE), to our best knowledge, which is currently the highest activity of MOF‐based catalyst for eNRR reported in the literature.

Exploring Zeolite Potential for Hydrofluorocarbon Capture and Recycling: Insights from Molecular Simulations

The need for efficient separation of hydrofluorocarbons for recycling and environmental protection is critical due to their substantial impact on global warming. However, conventional methods such as cryogenic distillation face significant limitations due to the azeotropic behavior of many of these hydrofluorocarbons. This study evaluates the adsorption behavior of various hydrofluorocarbons in zeolite structures, specifically Linde Type A (3A, 4A, and 5A) and Faujasite Type X (13X), using molecular dynamics and grand canonical Monte Carlo simulations. The simulations were validated against experimental data, confirming the reliability of the computational models. Adsorption isotherms were fitted using the Langmuir-Freundlich model to describe the adsorption behavior across different pressures. Focusing on fluoromethane derivatives, the study highlighted key interactions and adsorption capacities in various zeolites. The isotherms of various hydrofluorocarbons in zeolite 13X were explored, revealing differential adsorption based on molecular structure. The potential for using zeolite 13X and 5A to separate refrigerant mixtures was also studied, showing distinct selectivity patterns. Additionally, the temperature dependence of adsorption isotherms and isosteric heat was studied to gain insights into the thermodynamics of the adsorption processes. Key results indicate that zeolite 13X demonstrates strong cation-fluorine interactions, particularly effective for the adsorption of large hydrofluorocarbon molecules, which preferentially occupy 12-membered ring windows. In contrast, zeolite 5A exhibited predominant hydrogen bonding interactions at low pressures, with hydrofluorocarbon molecules occupying the smaller 8-membered ring windows. These findings underscore the selective adsorption capabilities of these zeolites, highlighting their potential application in hydrofluorocarbon separation and recycling processes.

CO2 adsorption on fluorinated covalent triazine frameworks (CTFs): Structure remodeling and performance enhancement

In consideration of the fact that covalent triazine frameworks (CTFs) have shown great potential and application prospects as CO2 adsorbent to alleviate the greenhouse effect and climate change by adsorption process for carbon emissions, a kind of promising activated fluorinated covalent triazine frameworks (referred to O-CTFs) was prepared as the adsorbent to enhance CO2 adsorption. The O-CTFs was prepared by structure remodeling of the fluorinated CTFs based on a series of ring-opening, substitution and polymerization reactions. The remodeling mechanism was revealed by theoretical calculations and those characterization methods of SEM, BET, EDS, FTIR, XPS, 13C-NMR and HRMS. Subsequently, the adsorption thermodynamics and kinetics of CO2 on the CTFs and O-CTFs were systematically investigated to reveal the influence of structure remodeling on CO2 adsorption behaviors. The results showed that the structure remodeling developed porous structure by forming more mesopores and micropores, then modified surface group distribution by forming new nitrogen- and oxygen-containing groups such as pyridine and pyrrole rings. The increase of pore volume, especially micropore volume, resulted in the dynamic capacity promotion by 217.5 % at 273 K. And the dual screening effects of surface group distribution and porous structure led to the CO2/N2 selectivity improvement by 202.4 %. Then the amount increase of the mesopores promoted the rate increase of CO2 adsorption by 59.9 % by means of accelerating the internal diffusion of CO2 in porous structure. In addition, the isosteric heat of adsorption decreased by 10.0 %, meaning that CO2 molecules were easily desorbed from the O-CTFs. These are beneficial for the preparation of promising CO2 adsorbent and extended application of CO2 adsorption processes.

Improved CO2 capture capacity of waste sawmill dust derived activated carbon employing novel high-pressure CO2 activation

The porosity of activated carbon is significantly influenced by both the precursor biomass and the activation parameters. Waste sawmill wood (WSW) dust, an abundantly available precursor from the furniture manufacturing, construction, carpentry, and shipbuilding industries, was collected, dried, pulverized, carbonized, and activated using steam and a novel high-pressure CO2 activation approach. Activation was performed in a tubular furnace at 800 °C with a pure CO2 flow for 90 min at 1 MPa pressure (WSW-A800-CO2-90 min-1 MPa). Another activated carbon sample was synthesized from the same precursor at atmospheric pressure using steam flow at 700 °C for 20 min (WSW-A700-Steam-20 min). XRD and FTIR analyses were conducted to compare the structural information of both samples. Additionally, the thermal characteristics of the samples were determined by measuring their specific heat capacities. N2 and CO2 adsorption experiments were performed to investigate the porous properties and CO2 capture capacities of the synthesized samples. The activated carbon synthesized in a pressurized CO2 environment produced a BET surface area of 684 m2/g, while steam activation achieved a BET surface area of 947 m2/g. Interestingly, despite the lower surface area of the CO2-activated sample, it exhibited a higher CO2 adsorption capacity (106.29 mg/g at 5 °C and 110 kPa) compared to the steam-activated carbon due to its unique pore size distribution. The experimental CO2 adsorption data were also correlated with Langmuir, Freundlich, and modified Dubinin-Astakhov (D-A) models to elucidate the CO2 capture parameters, such as isosteric heat of adsorption, activation energy, and Gibbs free energy.

A study on the thermal behavior of coal gangue mountains under airflow influence based on MD and CFD simulations

The long-term accumulation of coal gangue can lead to an increase in internal temperature. If the temperature becomes excessive, it can cause spontaneous combustion, posing serious environmental risks. The process is significantly influenced by external airflow. This study analyzes the thermodynamic properties and oxidation heat release rate of coal gangue samples through laboratory experiments. Subsequently, molecular dynamics (MD) simulations are used to investigate the mechanism of oxidation heat release during the heating process of coal gangue under varying oxygen supply conditions. Based on these findings, a coupled three-field model for the heating process of coal gangue mountains is developed. Using computational fluid dynamics (CFD) methods, transient simulations are conducted to analyze the internal thermal behavior of coal gangue mountains under the influence of external airflow, clarifying the risks of spontaneous combustion. The results indicate that after reaching T2 (295.16 °C), coal gangue enters an accelerated oxidation phase, with an increased heat release rate, heightening the risk of spontaneous combustion. The oxidation heat release rate of coal gangue accelerates with rising temperature and oxygen concentration, entering a rapid reaction phase after 300 °C, with a sharp increase in reaction rate. Compared to N2, coal gangue surfaces exhibit stronger adsorption of O2, and temperature changes affect N2 diffusion more sensitively (O2 diffusion coefficient increases by 0.312 Å2/ps, N2 diffusion coefficient increases by 0.334 Å2/ps). The isosteric heat of O2 adsorption in coal gangue decreases significantly with increasing adsorption amount, and higher temperatures hinder competitive adsorption of O2. The temperature in the deep and foot areas of the coal gangue mountains is lower, while the middle and upper areas near the slope surface exhibit higher temperatures, indicating a higher risk of spontaneous combustion in these regions. When environmental wind speed is too high or too low, both the internal temperature of the coal gangue mountains and the area of spontaneous combustion risk zones decrease. At a wind speed of 3 m/s, the spontaneous combustion risk zone reaches its maximum area of 73.47 m2, but when the wind speed increases to 7 m/s, the risk area decreases to 65.72 m2.

A model characterising the fractal supercritical adsorption behaviour of methane in shale: Incorporating principles, methods, and applications

The pore structure of shale is patently heterogeneous, with a conventional adsorption model being difficult to characterise the complex adsorption behavior of methane in shale. Therefore, a model is being proposed to characterise the fractal supercritical adsorption behavior of methane in shale. The principles and derivation of the model have been described in detail. The results showed that the adsorption characteristic parameters relating to different scale pores were affected by temperature and fractal dimension to different degrees. In addition, the relationship between isosteric heat of adsorption (qst) and adsorption capacity of different samples revealed different trends. The absolute values of ΔS of FC-66 and FC-72 decreased linearly. This might have been because of the fact that the adsorption saturation’s inflection point, which caused a fall in the absolute value of the entropy change (ΔS), was not reached. Compared with traditional adsorption models, the proposed model could reflect menthane’s adsorption in shale more accurately. The research results provide theoretical support for the evaluation of deep shale gas reserves, including the optimisation of exploitation strategies.

Differential adsorption of H2S/CH4 by bituminous coal and its competitive adsorption properties

To investigate the adsorption characteristics and competitive adsorption patterns of H2S and CH4 in coal seams, we conducted a combined experimental and molecular simulation study using Ningxia Shuangma bituminous coal as the research subject. The experiments examined the adsorption of single-component H2S and CH4 gases at different temperatures and pressures, while the molecular model of bituminous coal was used to analyze the adsorption patterns of binary gas mixtures under competing conditions. Our experimental results demonstrate that both H2S and CH4 follow Langmuir’s model, with their saturated adsorption positively correlated with pressure but negatively correlated with temperature. Moreover, under identical conditions, H2S exhibits 2.43 times higher saturated adsorption than CH4. Molecular simulations reveal that temperature has a greater impact on H2S compared to CH4; both gases undergo reversible physisorption, where isosteric heat of adsorption decreases linearly with increasing amount of adsorbate molecules; interaction energy for H2S is larger in absolute value than that for CH4, indicating its stronger affinity towards coal surfaces; regarding binary component adsorption, an increase in proportion of H2S within the gas mixture leads to higher saturation adsorptions for both the mixture itself and individual H2S molecules while decreasing saturation adsorption for CH4; Coal adsorption selectivity factor for H2S/CH4 > 1. The preferential occupation of high-energy adsorption sites is more likely to be observed for H2S. The adsorption capacity and competitive adsorption capacity of H2S were greater than that of CH4.

Modeling of adsorptive treatment of lead (II) ions contaminated effluents using cashew nut shell alkali activated carbon: Batch kinetic, isothermal and thermodynamic studies

The numerical study of the decontamination of lead(II) ions-rich effluent employing activated carbon derived from cashew nut shell was the central focus of this work. Chemical activation with zinc chloride (ZnCl2) was used to produce powdered activated carbon at optimized activation conditions of impregnation ratio (0.531), activation temperature (1083 K) and activation time (63min). The physiochemical properties of raw and activated cashew nut shell were determined using Fourier transform infrared spectroscopy, scanning, X-ray diffractor (XRD), scanning electron microscopy (SEM), and Brunauer-Emmet-Teller (BET) analyses. Batch adsorption experiments were performed at varied process conditions of temperature (303–323) K, contact time (5–80min), and initial lead(II) ion concentrations (100–400 mg.L−1). The adsorption behavior of the batch–type operation was mathematically described in the form of non-linear parabolic partial differential equations (PDE’S) incorporating film, pore and surface diffusion mechanisms. The batch mathematical model was solved by implementing a custom MATLAB program-OkiyNwabannebatch and calibrated to predict the desired response (percentage removal) using measured adsorption data. The equilibrium adsorption, kinetics and thermodynamics of lead(II) ions adsorption onto activated cashew nut shell were also assessed using nonlinear isotherm, kinetic and thermodynamic models. Sensitivity analysis unveiled that temperature with sensitivity value of 37.31 % had a predominant effect on the model performance. The simulated equilibrium data was well explicated by the Freundlich model for lead(II) ions adsorption onto activated cashew nut shell. The pseudo-second order kinetic model best reproduced the simulated adsorption data for lead(II) ions uptake by cashew nut shell adsorbent. Likewise, the kinetic data followed Boyd model, indicating that the adsorption process is controlled by external (film) diffusion for the uptake of lead(II) ions by alkali activated cashew nut shell. Thermodynamic analysis using the Gibbs and Van’t Hoff’s models indicated that lead(II) ions adsorption by modified cashew nut shell is spontaneous and exothermic. The physical nature of the adsorption process was elucidated from the low values of the isosteric heats of adsorption (ΔHX) evaluated (<80 kJ mol−1). This study showed that zinc chloride activated cashew nut shell has good potential to be used as a cost-effective and efficient adsorbent for the uptake of lead(II) ions from aqueous solution.

Study on the variability of oxygen adsorption behavior in coal gangue based on pore size structure

To investigate the adsorption and migration behavior of oxygen in coal gangue with different pore sizes, this study characterizes the multiscale morphology of coal gangue pores and fractures using SEM NMR, and low-temperature N2 (77 K) adsorption methods. As well, the study simulates the adsorption and diffusion behavior of O2 within the pore structures of coal gangue based on GCMC and MD methods. The study examines the oxygen adsorption characteristics across different pore sizes and analyzes the mass transfer mechanisms during oxygen diffusion. Results indicate that the pores in coal gangue are predominantly micropores within the 1–10 nm range. As pore size increases, the absolute adsorption amount of oxygen increases while the isosteric heat of adsorption decreases. The isosteric heat of adsorption in coal gangue models with different pore sizes is less than 42 kJ/mol, indicating the physical adsorption of oxygen within the pores. Oxygen shows adsorption layering perpendicular to the coal gangue surface, with adsorption density distribution differences decreasing and adsorption capacity weakening as pore size increases. The O2 adsorption isotherms in coal gangue follow Langmuir adsorption principles, with oxygen saturation adsorption decreasing as absolute adsorption increases. The confinement effect of coal gangue on oxygen weakens as pore size increases, and the impact of increasing pore size on oxygen diffusion is stronger than adsorption. These findings are significant for understanding the microscopic adsorption and diffusion behavior of O2 in coal gangue pores and fractures and are crucial for accurately preventing and managing spontaneous combustion in coal gangue piles.

Biogenic Synthesis of Cr‐Doped NiO/Clay Composite for Improved Dye Removal and CO2 Capture Studies

AbstractThe current work was designed to eliminate reactive yellow 18 dye (RY‐18) via adsorption from water, and CO2 from the gas stream, using the tragacanth gum‐based Cr doped NiO N.P.s/Clay (GCNC) composite. The one‐pot synthesis approach was used to produce the adsorbent, and physical and chemical properties were assessed using techniques like XRD, FTIR, UV‐visible spectroscopy, SEM, DLS, Zeta Potential, and adsorption–desorption isotherm. The GCNC composite demonstrated an impressive adsorption potential and percentage removal of 398 mg/g and 91.28%, respectively. Temkin and intraparticle diffusion models with R2 values of 0.98401 and 0.99918 were the most effective at fitting the experimental adsorption model. The thermodynamics parameters, including the change in enthalpy (H), entropy (S), and Gibbs free energy (G), demonstrated the endothermic and spontaneous nature of the adsorption process. A positive H value indicates an endothermic process, while a negative G value indicates a spontaneous process. According to the isotherms fitting model, the capacity for adsorbing CO2 at 25 °C and 1 atm was 4.8 mmol/g. The significant correlation between the slope in the log‐linear plot of the isosteric heat of adsorption and CO2 adsorption performance indicates that the isosteric heat of adsorption can be used as a predictive tool for CO2 adsorption performance. These significant results underscore the potential of the GCNC composite to revolutionize the water treatment field and CO2 capture, offering hope for a more sustainable and cleaner future.

High-performance metal-organic frameworks for efficient adsorption, controlled release, and membrane separation of organophosphate pesticides

Metal-organic frameworks (MOFs) are considered good choices for the absorption, separation, and release of various substances. The rapid increase in the number of MOFs being produced makes it impractical to conduct experimental research to identify the most promising candidates in these areas. Therefore, computational screening has emerged as a robust approach. We employed this approach to identify the most efficient MOFs for the removal, separation, and controlled release of organophosphorus pesticides, including diazinon, chlorpyrifos, and chlorpyrifos-methyl. From a database of approximately 14,000 MOFs, 584 MOFs with the largest cavity diameters were used in the screening process to evaluate promising candidates for each pesticide. Monte Carlo simulations were used to estimate the pesticide uptake capacities and isosteric heats of the selected MOFs. The structural properties of MOFs were correlated with their adsorption capacities and isosteric heats. Computational screening identified 325, 330, and 450 MOFs as potential absorbents and carriers for diazinon, chlorpyrifos-methyl, and chlorpyrifos, respectively. Additionally, it proposed 235, 254, and 135 MOFs as membranes for the effective separation of these organophosphorus pesticides. The reactivity of the pesticides was explored using quantum mechanics calculations. Molecular dynamics simulations of the top three MOFs with high uptake capacities for each pesticide were performed and analyzed to understand the interactions between the MOF, pesticide, and water molecules. The solvation-free energies of the pesticides were calculated for various solvents to identify the most effective solvent for desorbing pesticides from the MOFs, thereby enabling MOF regeneration.

Material-level experimental study on utilising ionic liquid/graphene composites for sorption heat storage

Sorption heat storage technology has recently sparked an increasing interest because of its advanced heat storage capabilities. However, material-level heat and mass transfer challenges persist. This work contributes to the field by the development of new sorption composite materials that are comprised ionic liquids (1-ethyl-3-methylimidazolium methanesulfonate and 1-ethyl-3-methylimidazolium chloride) impregnated in 1–5 2D-layered graphene host matrix. Their sorption, heat transfer, heat storage, and charging/discharging rate properties were experimentally investigated using both water and ethanol as adsorbates. The adsorption isotherms and kinetics for both the adsorbates onto the developed composites and the parent ionic liquids were experimentally measured at different temperatures. The isosteric heat of adsorption for all the studied pairs was determined using the Clausius-Clapeyron method, showing an increasing trend with an increasing uptake. They showed that the specific heat storage capacity reached 187.5 kJ/kg when water was used as the working sorption agent. The corresponding heat charging/discharging rates are significantly higher, 69 %-78 %, than pure ionic liquids. Compared to silica gel as a baseline sorbent, ionic liquid-graphene composites’ heat storage and transfer capacities are higher by three orders of magnitude. The thermal diffusivities of the developed composites were significantly higher than the baseline silica gel. These innovative sorption composites show great potential for improving thermal energy storage efficiency, making them suitable for applications in renewable energy systems, industrial processes, waste heat recovery, and climate control solutions. However, the developed composites achieved inferior performance compared to the silica gel baseline sorbent when using ethanol as a working fluid to utilise sub-zero ambient air as a heat source because of the relatively larger molecular size of ethanol.

N-doped carbon nanospheres synthesized from a newly designed eco-friendly sustainable polymer for highly selective CO2 capture.

N-doped carbon nanospheres and porous carbon were produced by a hydrothermal template and the activation of hexamethylenetetramine (HMTA as a nitrogen source and activator) and ZnCl2 (only as an activator) from a poly(Ri-S-ε-CL-PDMS) multiblock/graft copolymer produced using a renewable resource and eco-friendly autoxidation. N-doped carbon nanospheres (PPiSiHMTA) exhibited excellent CO2 adsorption (2.73mmol/g at 0°C and 0.15atm, 1.72mmol/g at 25°C and 0.15atm) and CO2/N2 selectivity (344-512). Despite the higher BET surface area and pore volume, porous carbon (PPiSi) showed low CO2 adsorption (1.21 and 0.71mmol/g, 0.15atm) and CO2/N2 selectivity (57 and 112). PPiSiHMTA and PPiSi have low isosteric heats of adsorption (Qst, 18-33kJ/mol) and stability in humid environments. In addition, PPiSiHMTA exhibited an excellent CO2 recycling performance. The experimental data on CO₂ adsorption was evaluated using various isotherm models, including Freundlich, Langmuir, Sips, and Temkin. The results demonstrated a nearly perfect fit between the Freundlich isotherm and the experimental data, indicating the heterogeneous nature of the adsorbent surfaces. Our study is promising for industrial applications, offering excellent CO2 adsorption, CO2/N2 selectivity, moisture stability, and porous material fabrication strategies.

Defective MOF incorporating CF3 functionality via fragmented linker co-assembly for high C2H6/C2H4 selectivity and C2H6 uptake

The production of high-purity ethylene requires an adsorbent with high C2H6/C2H4 selectivity, outstanding C2H6 adsorption, and facile C2H6 regeneration. Towards this goal, a series of novel defective CF3-functionalized metal–organic framework (MOF) materials (UiO-66-nCF3, n = 25, 50, 60, and 75) were synthesized by co-assembling the framework with terephthalic acid as the linker and various percentages (n) of CF3-functionalized ligands. The C2H6 adsorption strength increased as the density of CF3 groups increased. In particular, UiO-66-50CF3 exhibited high C2H6/C2H4 selectivity (2.04), excellent C2H6 adsorption (2.5 mmol/g), and modest C2H6 isosteric heat of adsorption (Qst) (∼28.9 kJ/mol). Additionally, the material exhibited high C2H6/C2H4 breakthrough selectivity (1.64) and large high-purity (>99.9 %) C2H4 productivity (7.32 LSTP kg−1) under dynamic flow conditions (C2H6/C2H4 = 1:15 (v/v)). UiO-66-50CF3 could readily be regenerated at room temperature, and demonstrated good hydrothermal stability in boiling water for 1 h and high thermal stability up to 500 °C. The incorporation of a high density of CF3 groups within a MOF via fragmented linker co-assembly is a promising strategy for developing adsorbents for C2H6/C2H4 separation.

Elucidating the separation role of C3N slit-pore on N2/CH4 in coalbed methane

A hybrid approach integrating molecular dynamics (MD) and Grand Canonical Monte Carlo (GCMC) simulations was employed to investigate the separation efficacy of N2/CH4 across various C3N slit apertures. MD simulations enabled the determination of separation selectivity and diffusion coefficients of N2/CH4, thereby aiding in the elucidation of the separation mechanism. On the other hand, GCMC simulations provided insights into the adsorption isotherms and isosteric heats of N2 and CH4 within the C3N slit. These findings reveal that the highest selectivity of N2 over CH4 occurs at the zigzag-edge C3N with a pore size of 6.2 Å. However, this selectivity is accompanied by the smallest diffusion coefficient, attributable to size sieving effects. As the pore diameter increases, more gas molecules can permeate into the pores, leading to a rise in both the maximum adsorption capacity and the isosteric heat of methane adsorption. With increasing pressure, gas molecules tend to reach saturation at higher pressure levels. Our study primarily centers on examining the separation of N2/CH4 across various C3N slit-pores, encompassing both adsorption and diffusion phenomena. These findings offer theoretical insights and comprehension for the experimental separation of coalbed methane utilizing cheaper carbon-based materials.

Ligand extension of aluminum fumarate metal-organic framework in transferring higher water for adsorption desalination

This article presents the synthesis and characterization of a new microporous metal organic framework (MOF) for adsorption desalination for the first time. The new MOF, designated as “Al-t,t-Ma”, is an analogue of aluminum fumarate (Al-Fum) and is fabricated via ligand extension method. Firstly, the MOF is synthesized, and then characterized by XRD, FTIR spectroscopy, TEM, SEM, TGA and N2 adsorption techniques. Secondly, the water adsorption experiments on the pristine Al-Fum and Al-t,t-Ma are performed for a wide temperature (30 °C ≤ T ≤ 80°C) and pressure (0 < P/Ps ≤ 0.9) ranges. The water adsorption isotherms, kinetics, hydro-thermal stabilities as well as the isosteric heat of adsorption (Qst) are evaluated. Thirdly, based on the experimentally confirmed isotherms, kinetics and isosteric heats data, the adsorption assisted desalination (AD) system is modelled and simulated. Finally, the performances of AD system employing Al-Fum and Al-t,t-Ma MOFs are calculated in terms of the performance ratio (PR) and specific daily water production (SDWP) under various half cycle times (100 s ≤ tcycle ≤ 1000 s) and regeneration temperatures (55°C ≤ Tregen ≤ 80°C). As compared with the pristine Al-Fum, the pore volume of Al-t,t-Ma MOF is found 115 % higher. The proposed Al-t,t-Ma MOF possesses higher water transfer (+57.5 % more) with promising hydro-thermal stability. Employing Al-t,t-Ma MOF as porous adsorbent, the SDWP is achieved 28 m3 per tonne of MOFs per day at the regeneration temperature of 55°C. These results confirm that Al-t,t-Ma MOF is a competent candidate for adsorption desalination.

Adsorption characteristics and separation behavior of binder and binderless zeolite LiX Pellets: O2, N2, and CO2

In adsorptive gas separation process design, optimal adsorbent selection acts as a critical factor in process efficiency. This study investigated the adsorption equilibria and kinetics of O2, N2, and CO2 (weak, medium and strong affinity, respectively) and the breakthrough performance of four commercial zeolite LiX pellets (one binderless and three binder zeolite LiX pellets) because the performance of pelletized zeolites becomes different by adding binders and pelletizing methods. The adsorption isotherms at 293–323 K and up to 100 kPa were correlated with the dual-site Langmuir and Sips models. For all adsorbents, the order of adsorption amount and isosteric heat of adsorption was CO2 ≫ N2 > O2. However, differences among the four zeolite pellets were also observed, showing the highest values of the binderless zeolite LiX pellet. Furthermore, the adsorption capacity was 20–25 % smaller for CO2 and 40–50 % smaller of N2 and O2 at 100 kPa compared to pure zeolite LiX powder. According to kinetic analysis using a non-isothermal diffusion model, the adsorption rate of N2 was faster than that of CO2 for all adsorbents, showing the order difference in the low-pressure range. The kinetic difference among the zeolite pellets resulted from the effects of heat of adsorption, heat dissipation, and thermal resistance. The breakthrough performance using N2 and O2 was mainly controlled by the adsorption capacity, showing almost constant breakthrough pattern regardless of the samples. This study suggests that detailed evaluation of pelletized adsorbent is essential before designing adsorptive processes because performance of adsorbent powder would lead to under-design of the process. (255 words)

Two-way coupling dynamics of CH4 adsorption and coal matrix deformation: Insights from hybrid GCMC/MD simulations

CH4 adsorption can deform coal microporous structures, subsequently altering adsorption isotherms. To unravel this intricate interplay at a microscopic level, we use a hybrid Grand Canonical Monte Carlo/Molecular Dynamics (GCMC/MD) simulation at 313.15 K and pressures up to 500 bar on five independent amorphous coal matrix models. Our results reveal that CH4 adsorption increases pore volume and porosity primarily by generating additional pores of similar sizes to those present in coal matrices, thereby maintaining a consistent average pore size across different pressures. The volumetric strain has a linear correlation with CH4 loading, with volumetric swelling amount approximating the expansion of CH4-occupiable pore volume, but less than He-occupiable pore volume which results in increased matrix skeletal density. Local radial density distribution of carbon atoms indicates that the immediate environment around carbon atoms remains unchanged. In a flexible matrix, the energy released during CH4 adsorption is partially absorbed by matrix deformation, resulting in a lower isosteric heat of adsorption compared to a rigid matrix, which suggests easier desorption. This study provides new insights into the mutual relationship between CH4 adsorption and coal matrix deformation, shedding lights on the complex interactions of various hydrocarbons with geomaterials.

Comparative Modelling, Sensitivity Analysis and Thermodynamics Study of the Adsorption Characteristics of Dried Nauclea latifolia Medicinal Leaves

The adsorption characteristics of Nauclea latifolia medicinal leaves were examined across selected temperatures (30–50°C) and water activity levels (0.044–0.900) to assess its storage stability. Both univariate semi-empirical and multivariate statistical models were comparatively employed to represent and predict the observed adsorption characteristics. Additionally, sensitivity analysis was conducted to evaluate the dependence of the adsorption characteristics (that is, equilibrium moisture content (EMC (g/g d.b.)) on temperature and water activity storage factors. The net isosteric heat and entropy of adsorption were also determined alongside compensation theory values. The results indicated that EMC decreased with increasing temperature and increased with rising water activity. The minimum and maximum EMC values of 0.015 and 0.221 g/g d.b. were observed at 50°C. The safe moisture content for storing dried Nauclea latifolia medicinal leaves was 12.6 (g/g d.b.) at 30 to 40 °C and 9 (g/g d.b.) at 50°C. Amongst the models tested, the Peleg model demonstrated best performance, with its R² values ranging from 0.9897 to 0.994 and RMSE values between 0.0039 and 0.0129. Sensitivity analysis revealed that EMC is more sensitive to water activity than to temperature. The net isosteric heat and entropy of adsorption decreased with increasing EMC, indicating that the process was enthalpy-driven. In conclusion, the findings underscore the importance of environmental management in maintaining the storage properties of Nauclea latifolia medicinal leaves. The results of the models are useful in guiding the optimal storage conditions and the design of tailored storage facilities for Nauclea latifolia medicinal leaves.