Adsorption最新文献

The urgent need for negative emissions technologies has positioned Direct Air Capture (DAC) as a critical climate solution, yet the ultra-dilute nature of atmospheric CO₂ demands adsorbents with exceptional affinity and selectivity. Among these, the metal-organic framework MOF-74 has emerged as a leading contender, renowned for its record-high CO₂ uptake at low pressures, driven by a high density of open metal sites (OMS). This review critically assesses the journey of MOF-74 from its promising intrinsic properties toward practical DAC application. We elucidate the central paradox of the material: the very OMS that grant its superior CO₂ capacity also render it highly susceptible to hydrolytic degradation in ambient humidity, creating a significant practicality gap. The analysis systematically explores advanced material engineering strategies-including metal node selection, chemical functionalization of linkers, and composite formation—to navigate the critical trade-off between capacity and stability. Furthermore, we highlight the pivotal role of computational modeling and machine learning in accelerating the design of next-generation, water-resistant variants. While pilot-scale validations demonstrate MOF-74’s potential for efficient, low-energy DAC cycles, economic viability and scalable synthesis remain hurdles. We conclude that the path forward hinges on a multidisciplinary research agenda focused on developing robust, multi-metallic frameworks and advanced composite systems, underpinned by holistic sustainability assessments to translate the immense promise of MOF-74 into a practical DAC technology.

Chiral metal-organic frameworks (CMOFs) are promising materials for catalysis, chromatography, and sensor applications. Typically, chirality in such frameworks is achieved by using chiral ligands. However, there are rare examples of CMOFs that form without any chiral source, usually via spontaneous symmetry breaking, resulting in supramolecular chirality. Germanium oxide framework SU-MB exhibits a unique mechanism of chirality emergence: during synthesis, only micropores of one handedness are selectively filled. This paper investigates the adsorption of limonene and α-pinene enantiomers on SU-MB. The framework demonstrated consistent enantioselectivity for both pairs of enantiomers, with a higher selectivity coefficient observed for α-pinenes than for limonenes. This difference arises from distinct trends in the isosteric heats of adsorption (Q_st): for limonenes and (−)-α-pinene, Q_st approaches the heat of liquefaction with increasing adsorption, whereas for (+)-α-pinene, Q_st remains unchanged. These findings show that even a non-chiral crystal without chiral centers can exhibit enantioselectivity in adsorption processes, because of helical pores of one handedness.

Efficient CO₂ separation from biogas is essential for enhancing methane quality and supporting sustainable energy production. In this study, CO₂/CH₄ separation is investigated using a one-dimensional computational fluid dynamics model implemented in COMSOL Multiphysics and validated against published experimental data for MIL-53(Al). Several metal–organic frameworks, including MOF-303, MIL-160, aluminum fumarate, HKUST-1, and UIO-66, are systematically compared under identical operating conditions. The results demonstrate that MOF-303 exhibits the highest CO₂ selectivity and adsorption capacity, achieving an equilibrium uptake of 12.35 mol/kg at 15 bar and 298 K, significantly outperforming the other investigated materials. Building on this finding, the model is further applied to examine the influence of bed geometry on CO₂ capture using MOF-303. The analysis reveals that increasing bed length while reducing bed diameter substantially enhances adsorption performance, with a maximum uptake of 42.15 kg CO₂ per kg of MOF per day at an optimized geometry. These results demonstrate the combined importance of adsorbent selection and bed design and provide new insights into the optimization of MOF-based PSA systems for high-efficiency biogas upgrading.

A three-tower, nine-step vacuum pressure swing adsorption (VPSA) process coupled with the partial flushing equalization (PFE) and natural aspiration/exhaust (NA/NE) technology was proposed and used for largest industrial-scale 80% oxygen production project in China in this study. The performance of the VPSA system during one whole year showed an obvious seasonal variation, being directly related to the atmosphere humidity and temperature. Correlation analysis between working condition and three performance indicators indicated that feed water and adsorber tower temperature exhibited highly similar linear profiles with respect to O₂ recovery and productivity, whereas contrary trend was observed for product flow rate. To achieve the relative constant product flow rate of 56,000 Nm³/h and O₂ purity of 83%, two approaches were used in the case of low temperature: decreasing the frequency of blower or increasing the vacuum level. Either way, the obtained higher adsorption/desorption pressure (P_H/P_L) ratio can indeed increase the O₂ purity. Moreover, the typical half-V-shaped profile of energy consumption with increase in adsorber temperature indicated that excessively high or low adsorber tower temperatures led to higher energy consumption. Although higher energy consumption was obtained for lower adsorber temperature of 21–30 ℃ in winter due to the NA process, the competitive energy consumption of 0.28–0.31 kWh/m³ contributed to the economic feasibility of the three-tower, nine-step VPSA process for simultaneous achieving higher O₂ yield and lower energy consumption.

Gas adsorption kinetics can significantly affect column size as well as the purity and recovery of products obtained from adsorption-based separation processes. Therefore, accurate adsorption kinetics are essential for designing pressure swing adsorption (PSA) processes. To obtain reliable kinetic parameters, it is crucial to employ reliable measurement methods and efficient yet accurate data evaluation procedures. In this study, we measured the equilibrium and kinetic data for CO_2, CH₄, N₂ on ZSM-5 at three temperatures at pressures up to 120 kPa using a commercial volumetric-based system to evaluate the adsorbent’s potential for natural gas upgrading. The equilibrium data were analysed by fitting them to Langmuir equations with CH₄/N₂ and CO₂/CH₄ selectivities evaluated using the ideal adsorbed solution theory (IAST). A robust and efficient procedure to extract kinetic parameters using the non-isothermal Fickian diffusion (FD) model was developed. This procedure standardises the method for determining the actual start time of the adsorption for each kinetic measurement and for estimating initial guesses for all involved parameters. The goodness of data regression was evaluated by analysing sorted residual plots of the experimental and regressed data, as well as the uncertainties of the extracted parameters. By applying the procedure, kinetic parameters for gases on ZSM-5 were assessed. Results indicate that ZSM-5 exhibits favourable adsorption kinetics and equilibrium characteristics for CH₄/N₂ separation.

When using water to cool adsorption cooling systems, it is necessary to have a permanent source of cold water or to utilize cooling towers, which consume large amounts of water due to evaporation in the process of evaporative water cooling. Therefore, many scientists focus on how to use sustainable sources of cold water, such as geothermal cooling, which is one of the most promising sources for energy system applications. The study presents a novel method for combining solar heating and geothermal cooling in Lebanon, utilizing adsorption cooling to enhance the efficient use of renewable resources. Geothermal cooling energy is primarily used to cool the condenser of the adsorption chiller, in addition to removing the heat of adsorption during the adsorption process. The effects of the diameter and length of the ground-cooling water pipes, as well as the water velocity, on the ground-cooling water temperature are investigated. Then, the impact of changes in ground-cooling water temperature on the performance of the adsorption cooling system is studied. The paper also presents theoretically the performance of the adsorption cooling system in Lebanon’s climate. The results illustrate that coupling geothermal cooling with a solar-powered adsorption cooling system increases the cooling capacity to 21.6 kW, with an improvement of about 44% compared to the traditional adsorption system with a cooling tower. The proposed combination raises the coefficient of performance (COP) to 0.52, with an enhancement of about 11.6% at a regeneration temperature of 85 °C. An additional advantage of this coupling is that the system can operate efficiently at a low hot source temperature of 50 °C with a COP of 0.55. This research demonstrates that solar energy and geothermal cooling sources can be efficiently utilized to power hybrid adsorption cooling systems. This approach not only promotes electrical power savings but also leverages renewable and environmentally friendly resources, potentially advancing these industries in the future.

Metal–organic frameworks (MOFs) are highly porous and crystalline materials synthesized from metal ions and organic ligands. They have received attention from researchers in recent years due to their enormous applications, such as separation, sensors, gas storage, and catalysis. MOFs are categorized as nanoporous, mesoporous, and microporous based on the size of the pores. Functionality of MOFs depends on their pore size and overall charge. BTEX, a subclass of volatile organic compounds found in air, is classified as a hazardous pollutant because of its toxic, carcinogenic, and mutagenic nature. One practical strategy for protecting the environment is the sequestration of multi-component BTEX using MOFs as sorbents. This review discusses the classification of MOFs and highlights the green and economical methodologies adopted for the synthesis of MOFs in order to facilitate their commercialization. This article also presents an overview of the adsorption of BTEX using various types of MOFs. More significantly, plausible processes for the adsorption or interaction of BTEX compounds with MOFs are discussed. The various kinds of interaction, including hydrophobic interactions, π–π stacking, hydrogen bonding, interaction at open metal site, and electrostatic interaction, are discussed. These processes are usually impacted by the ligands' structure and functionalization, the MOFs functionalization, the pore size, and the surface structure of the MOF.

Managing wastewater in industrial laundries poses a significant challenge, particularly in the removal of emerging contaminants such as phenolic compounds. The performance of a two-stage process combining ultrafiltration followed by adsorption using modified activated carbon was studied for the removal of nonylphenol ethoxylate (NPEO_3-17) from real laundry wastewater. The use of ultrafiltration as a pretreatment allowed removing solids and colloids before adsorption. Ultrafiltration led to a reduction in total suspended solids from 14.0 ± 2.1 to 3.0 ± 1.3 mg.L⁻¹ and turbidity from 110 ± 1.4 to 1.8 ± 0.9 NTU. Additionally, NPEO_3-17 concentration decreased from 1095 ± 50 µg.L⁻¹ to 534 ± 78 µg.L⁻¹, whereas the chemical oxygen demand (COD) concentration passed from 585 ± 14 mg.L⁻¹ to 281 ± 9 mg.L⁻¹ in the permeate. The ultrafiltration permeate was subsequently treated by dynamic adsorption. The adsorption process was designed and optimized considering parameters such as hydraulic retention time (HRT), initial feed temperature, and column height-to-diameter (H/D) ratio. HRT was found to be the most important parameter contributing significantly to NPEO_3-17 and COD removal. Under the optimal conditions (HRT of 9.6 min, a temperature of 20 °C, and an H/D ratio of 6.9) using Box-Behnken Design methodology, 99% and 82% of NPEO_3-17 and COD were removed, respectively. The breakthrough behavior of the adsorption column was further analyzed using six classical models including Bohart–Adams, Yoon–Nelson, Thomas, Wolborska, Yan, and Clark, to interpret the dynamic adsorption kinetics and predict column performance. The Bohart-Adams and Wolborska models described very well the adsorption process for NPEO_3-17. Results demonstrated that the modified activated carbon maintained NPEO_3-17 levels below the reuse threshold (< 200 µg.L⁻¹) for water reuse, even after treating nearly 100 L of ultrafiltered water, confirming the efficiency and long-term stability of the hybrid ultrafiltration–adsorption system.

Graphical abstract

The pressure swing adsorption (PSA) process has a wide range of applications for CO₂ capture from flue gas, due to the advantages of simple operation, low investment and energy consumption. However, existing research results have shown that conventional single-stage PSA typically cannot achieve 95% purity CO₂ with 90% recovery using most commercial adsorbents. Dual reflux pressure swing adsorption (DR-PSA) is a special process that combines stripping and enriching PSA, where light and heavy products with high purity and high recovery can be obtained simultaneously. However, its industrial applications are limited by the problems of discontinuous feeding and high energy consumption. To overcome these limitations, a 4-bed continuous DR-PSA was developed and simulated using a model validated against published experimental data, with simulated flue gas (CO₂/N₂ = 15%/85%) as the feed and silica gel as the adsorbent. After comparing internal state variables, four key parameters, including feed flow rate, step duration, light reflux-to-feed ratio, and feed position, were studied in detail. The results indicate that the proposed process can achieve CO₂ purity of 96.42% with 96.52% recovery, N₂ purity of 99.40% with 99.40% recovery, a productivity of 0.4607 mol CO₂/kg/h, and a specific energy consumption of 1.172 GJ/t CO₂. The process demonstrates significantly superior specific energy consumption compared to prior studies.