On the mechanism of water adsorption in carbon micropores – A molecular simulation study

Liu, Lumeng; Zeng, Yonghong; Tan, Shiliang; Do, D.D.; Nicholson, D.; Liu, Junjie

doi:10.1016/j.cej.2018.09.160

Cited by 36 publications

(7 citation statements)

References 29 publications

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“…From the perspective of experiment, it is not difficult to obtain the water adsorption isotherms of several adsorbents, but it is impractical to synthesize and test thousands of adsorbents to identify the best performer for water adsorption since ∼100 000 MOFs have been synthesized and documented in the Cambridge Structure Database. 24 From the perspective of computation, water adsorption isotherms of adsorbents may be obtained from a molecular simulation with the crystal structure of adsorbents, 25,26 which will greatly reduce the experimental time and cost in high-efficiency discovery of the top performers. 27,28 Unfortunately, the extremely high computational cost of a grand canonical Monte Carlo (GCMC) molecular simulation for water adsorption isotherm prediction resulting from ultra-slow equilibrium convergence and local free-energy minimum trap [29][30][31][32] add up to the impossibility of large-scale prediction of water adsorption performance.…”

Section: Introductionmentioning

confidence: 99%

Machine learning-assisted prediction of water adsorption isotherms and cooling performance

Liu¹,

Shen²,

Cai³

et al. 2023

J. Mater. Chem. A

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Section: Introductionmentioning

confidence: 99%

Machine learning-assisted prediction of water adsorption isotherms and cooling performance

Liu¹,

Shen²,

Cai³

et al. 2023

J. Mater. Chem. A

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“…Activated carbons (ACs), as a class of efficient air purification material with high specific surface area and pore volume, are widely used to remove volatile organic compounds (VOCs) and industrial toxic chemicals (TICs) from air streams. − Water vapor competitive adsorption usually occurs in the adsorption and separation process and would reduce the VOC or TIC adsorption capacities and separation efficiencies on porous ACs. − Thus, as the important thermodynamic basis of competitive adsorption, numerous investigations concerning single-component water vapor adsorption/desorption behavior on ACs have been carried out in recent years. − It is well-known that the surface oxygen-containing functional group and pore structure have an obvious influence on the water vapor adsorption equilibrium . Do et al suggested that the water vapor adsorption amount increased with an increase in the content of the surface oxygen-containing functional group due to the hydrogen bonding interactions between water molecules and functional groups at lower relative humidity (RH) ( P / P 0 < 0.35), while it would be dependent on the pore volume due to capillary condensation at higher RH. ,,− However, studies of the water vapor adsorption kinetics inside the particle and water vapor desorption equilibrium on ACs are still scarce.…”

Section: Introductionmentioning

confidence: 99%

Water Vapor Adsorption/Desorption Behaviors on Activated Carbon Particles and Fixed Beds: Isotherms, Kinetics, and Axial Temperature

Zheng,

Niu,

Kang

et al. 2023

Ind. Eng. Chem. Res.

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Relative humidity and moisture content are the key factors affecting the adsorption abilities of activated carbons (ACs) against these physisorption-type volatile organic compounds and industrial toxic chemicals due to competitive adsorption. Water vapor adsorption/desorption behaviors on AC particles and fixed beds are of great interest in materials science, the chemical industry, and military chemistry. This work selected two typical ACs (AC and ASZM-T) used in chemical protection. Water vapor adsorption equilibrium, adsorption kinetics, dynamic adsorption/desorption curves, and axial temperature during the adsorption/desorption process were systemically investigated. Results show that water vapor adsorption–desorption isotherms belong to the “S” type with obvious triangular hysteresis loops. Adsorption curves at different temperatures almost overlap, proving the temperature-independence. Dynamic adsorption–desorption curves on the fixed beds could be divided into different stages. The duration of each stage and adsorption/desorption rate are mainly determined by the relative humidity and moisture content. The heat effect induced by water vapor adsorption/desorption could cause the fixed bed to be in a nonisothermal state, indicating that the heat transfer inside the fixed bed was mainly controlled by the water vapor mass transfer. It provides a theoretical basis for temperature-induced low-concentration multicomponent competitive adsorption under relative humidity and moisture content levels.

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“…With regard to the pore model in water adsorption, experiment data ,, and simulation studies − have shown that water molecules readily fill the confined space of graphitic pores with polar functional groups grafted on the pore walls or the edges of graphene layers. For ultrafine graphitic pores, water can fill their volume even in the absence of functional groups − because the enhanced interaction potential between water and these pores (due to the overlapping of potentials exerted by the opposite pore walls) is comparable to the water–water interaction potential.…”

Section: Introductionmentioning

confidence: 99%

Distinct Behavior of SPC/E, TIP4P/2005, and TIP5P Water Adsorbates in Graphitic Pores

Loi,

2023

Ind. Eng. Chem. Res.

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Knowledge of the mechanism of water adsorption in activated carbons is essential for the design of the adsorptive separation process because water molecules form clusters at strong sites within porous structures with subsequent growth to fill the entire pore space, interfering with the removal of undesired components from a gaseous mixture. To this end, computer simulation is a valuable tool to explore the mechanism of water adsorption to delineate the various processes occurring in a given pore. However, there exists many intermolecular potential models for water, each with its own advantages and disadvantages, and an obvious question is raised: do they describe the same macroscopic behavior (isotherm and isosteric heat) and the underlying microscopic mechanism? Three of the most common nonpolarizable, rigid force fields for water, SPC/E, TIP4P/2005, and TIP5P models, are chosen to investigate adsorption of water in graphitic pores. The first two models describe well the thermodynamic properties of the bulk liquid, while TIP5P properly models the tetrahedral structure of water to explicitly account for the two lone pairs of electrons, in contrast to the planar structure of the first two models. With respect to modeling of graphitic pores, we chose two models, one of which has an infinite extent along the directions parallel to the pore walls and the other has a finite extent to explore the effects of the pore opening on the adsorption behavior. It was found that with the appropriate choice of temperatures for each water potential model, only the TIP5P model in finite graphitic pores captures the second-order pore filling mechanism of water in microporous carbons as observed experimentally, suggesting the importance of the molecular shape in the packing of the adsorbate and its role in properly describing the adsorption isotherm and isosteric heat.

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On the mechanism of water adsorption in carbon micropores – A molecular simulation study

Cited by 36 publications

References 29 publications

Machine learning-assisted prediction of water adsorption isotherms and cooling performance

Machine learning-assisted prediction of water adsorption isotherms and cooling performance

Water Vapor Adsorption/Desorption Behaviors on Activated Carbon Particles and Fixed Beds: Isotherms, Kinetics, and Axial Temperature

Distinct Behavior of SPC/E, TIP4P/2005, and TIP5P Water Adsorbates in Graphitic Pores

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