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Molecules
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Exploration of the Separation Processes in Nanomaterials
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Exploration of the Separation Processes in Nanomaterials

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Inorganic Chemistry".

Deadline for manuscript submissions: closed (12 July 2023) | Viewed by 12489

Special Issue Editors

Dr. Xuechao Gao

E-Mail Website
Guest Editor
College of Chemical Engineering, Nanjing Tech University, Nanjing 211816, China
Interests: membrane process; gas separation; inorganic membrane; adsorption and diffusion; transport resistance
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Lang Liu

E-Mail Website
Guest Editor
Key Laboratory of Low-Grade Energy Utilization Technologies and Systems, Ministry of Education, School of Energy and Power Engineering, Chongqing University, Chongqing, China
Interests: interfacial resistance; water transport; membrane separation; adsorptive separation; nanoporous materials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Membrane and adsorption technologies are solutions with great potential to avoid the high-energy consumption, secondary pollution, and complex chemical reactions involved in the separation field. Owning to significant advances in material synthesis, numerous classic and novel nanomaterials have been synthesized as membranes and adsorbents to achieve high performance of separation, such as silica, zeolite, MOFs, and carbons, where the pore framework and geometry could be specifically manipulated according to the properties of guest molecules. However, the understanding and exploration of the separation process in nanomaterials is still far from satisfactory. This is largely due to the inadequacy of the systematic research on this subject, where the essential relationship between the physical properties and chemical heterogeneousity of nanomaterials and their separation performance needs to be comprehensively revealed. Thereby, we are launching this Special Issue to call on nanomaterial and separation experts to explore the essential factors deciding the separation procedures in different nanomaterials.

The Special Issue on ”Exploration of the Separation Processes in Nanomaterials” aims to present recent advances that address the key challenges of membrane and adsorptive separation in different aspects. Topics include but are not limited to:

  • Novel nanopore synthesis
  • Molecular adsorption and transport
  • Membrane and adsorbent design
  • Computational fluid dynamics in membrane modules
  • Application of the membrane and adsorption unit
  • Fluid transport in a porous media
  • Separation mechanism analysis in nanopores

Process simulation of membrane and adsorption separation.

Dr. Xuechao Gao
Prof. Dr. Lang Liu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • membrane separation
  • adsorption and diffusion
  • molecular sieves
  • nanoporous membranes
  • separation mechanism

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Published Papers (6 papers)

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Research

11 pages, 2663 KiB  
Article
Coalescence and Break-Up Behaviors of Nanodroplets under AC Electric Field
by Fenhong Song, Ruifeng Chen, Gang Wang, Jing Fan and Hu Niu
Molecules 2023, 28(7), 3064; https://doi.org/10.3390/molecules28073064 - 29 Mar 2023
Cited by 6 | Viewed by 1797
Abstract
Water must be separated from water-in-oil (W/O) emulsion because of the corrosion it brings to the relative equipment in the process of transportation and storage. It is an effective method to apply external electric field to achieve high performance of separating small, dispersed [...] Read more.
Water must be separated from water-in-oil (W/O) emulsion because of the corrosion it brings to the relative equipment in the process of transportation and storage. It is an effective method to apply external electric field to achieve high performance of separating small, dispersed water droplets from W/O emulsion; however, the coalescing micromechanism of such small salty droplets under AC electric field is unclear. In this paper, molecular dynamics simulation was adopted to investigate the coalescence and separation process of two NaCl-aqueous droplets under AC electric field and discuss the effect of AC electric field frequency, as well as the time required for contacting, the critical electric field strength, the dynamic coalescence process and the stability of the final merged droplet. The results show that the critical electric field strength of the droplet coalescence increases with the increase of frequency, while the time required for droplet contacting becomes shorter. The shrinkage function curve was applied to characterize the droplet coalescence effect and it was found that the droplets coalescence and form a nearly spherical droplet under the AC electric field with a frequency of 1.25 GHz and strength of 0.5 V/nm. When the electric field frequency is 10 GHZ, the merged droplet presents a periodic fluctuation with the same period as the AC electric field, which mainly depends on the periodic movement of cations and anions under the AC electric field. The results can provide theoretical basis for the practical application of electrostatic demulsification technology in the petroleum or chemical industry from the microscopic perspective. Full article
(This article belongs to the Special Issue Exploration of the Separation Processes in Nanomaterials)
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13 pages, 2741 KiB  
Article
Naphthenic Acids Removal from Model Transformer Oil by Diethylamine Modified Resins
by Yan Wang, Peng Dou, Xiaofeng You, Qing Liu, Zhaoyang Fei, Xian Chen, Zhuxiu Zhang, Jihai Tang, Mifen Cui and Xu Qiao
Molecules 2023, 28(6), 2444; https://doi.org/10.3390/molecules28062444 - 7 Mar 2023
Cited by 1 | Viewed by 1623
Abstract
Resins have enormous potential in the removal of naphthenic acids (NAs) from transformer oil due to their rich porosity and high mechanical and diversified functionality, whereas their poor adsorption capacity limits application. In this work, the polystyrene–diethylamine resin (PS−DEA−x) was prepared by grafting [...] Read more.
Resins have enormous potential in the removal of naphthenic acids (NAs) from transformer oil due to their rich porosity and high mechanical and diversified functionality, whereas their poor adsorption capacity limits application. In this work, the polystyrene–diethylamine resin (PS−DEA−x) was prepared by grafting diethylamine (DEA) onto chloromethylated polystyrene (PS−Cl) resin to efficiently adsorb cyclopentane carboxylic acid from transformer oil for the first time. The characterization analysis results indicated that amine contents were significantly enhanced with the increase in DEA. Particularly, resin with a molar ratio of 1:5 depending on chloromethyl to DEA (PS−DEA−5) exhibited the highest amine contents and efficient adsorption of cyclopentane carboxylic acid (static adsorption capacity up to 110.0 mg/g), which was about 5 times higher than that of the pristine PS−Cl. The thermodynamic and kinetic studies showed that the adsorption behaviors could be well fitted to the Langmuir isotherm equation and pseudo−second−order rate equation. Moreover, it was found that 1 g of the PS−DEA−5 can decontaminate about 760 mL transformer oil to meet reuse standards by a continuous stream, indicating its potential application in industry. Full article
(This article belongs to the Special Issue Exploration of the Separation Processes in Nanomaterials)
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16 pages, 7824 KiB  
Article
Mechanism of Hexane Displaced by Supercritical Carbon Dioxide: Insights from Molecular Simulations
by Jiasheng Song, Zhuangying Zhu and Lang Liu
Molecules 2022, 27(23), 8340; https://doi.org/10.3390/molecules27238340 - 29 Nov 2022
Cited by 1 | Viewed by 1707
Abstract
Supercritical carbon dioxide (sCO2) has great potential for displacing shale oil as a result of its high solubility and low surface tension and viscosity, but the underlying mechanisms have remained unclear up to now. By conducting equilibrium molecular dynamics (EMD) simulations, [...] Read more.
Supercritical carbon dioxide (sCO2) has great potential for displacing shale oil as a result of its high solubility and low surface tension and viscosity, but the underlying mechanisms have remained unclear up to now. By conducting equilibrium molecular dynamics (EMD) simulations, we found that the displacing process could be divided into three steps: the CO2 molecules were firstly injected in the central region of shale slit, then tended to adsorb on the SiO2-OH wall surface and mix with hexane, resulting in loose hexane layer on the shale surface, and finally displaced hexane from the wall due to strong interactions between CO2 and wall. In that process, the displacing velocity and efficiency of hexane exhibit parabolic and increased trends with pressure, respectively. To gain deep insights into this phenomenon, we further performed non-equilibrium molecular dynamics (NEMD) simulations and found that both the Onsager coefficients of CO2 and hexane were correlated to increase with pressure, until the diffusion rate of hexane being suppressed by the highly dense distribution of CO2 molecules at 12 MPa. The rapid transportation of CO2 molecules in the binary components (CO2 and hexane) actually promoted the hexane diffusion, which facilitated hexane flowing out of the nanochannel and subsequently enhanced oil recovery efficiency. The displacing process could occur effectively at pressures higher than 7.5 MPa, after which the interaction energies of the CO2-wall were stronger than that of the hexane-wall. Taking displacing velocity and efficiency and hexane diffusion rate into consideration, the optimal injection pressure was found at 10.5 MPa in this work. This study provides detailed insights into CO2 displacing shale oil and is in favor of deepening the understanding of shale oil exploitation and utilization. Full article
(This article belongs to the Special Issue Exploration of the Separation Processes in Nanomaterials)
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18 pages, 6050 KiB  
Article
Enhancing the Performance of Evolutionary Algorithm by Differential Evolution for Optimizing Distillation Sequence
by Zehua Hu, Peilong Li and Yefei Liu
Molecules 2022, 27(12), 3802; https://doi.org/10.3390/molecules27123802 - 13 Jun 2022
Cited by 3 | Viewed by 1957
Abstract
Optimal synthesis of distillation sequence is a complex problem in chemical processes engineering, which involves process structure optimization and operation parameters optimization. The study of the synthesis of distillation sequence is a crucial step toward improving the efficiency of chemical processes and reducing [...] Read more.
Optimal synthesis of distillation sequence is a complex problem in chemical processes engineering, which involves process structure optimization and operation parameters optimization. The study of the synthesis of distillation sequence is a crucial step toward improving the efficiency of chemical processes and reducing greenhouse gas emissions. This work introduced the concept of binary tree to encode the distillation sequence. The performance of the six evolutionary algorithms was evaluated by solving a 14-component distillation sequence synthesis problem. The best algorithm was used to optimize the operation parameters of a triple-column distillation process. The total annual cost and CO2 emissions were considered as the metrics to evaluate the performance of triple-column distillation processes. As a result, NSGA-II-DE was found to be the best one of the six tested evolutionary algorithms. Then, NSGA-II-DE was applied to the distillation sequence optimization to find the best operating parameters, which led to a significant reduction in CO2 emission and total annual costs. Full article
(This article belongs to the Special Issue Exploration of the Separation Processes in Nanomaterials)
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19 pages, 5868 KiB  
Article
Impact of Impure Gas on CO2 Capture from Flue Gas Using Carbon Nanotubes: A Molecular Simulation Study
by Yiru Su, Siyao Liu and Xuechao Gao
Molecules 2022, 27(5), 1627; https://doi.org/10.3390/molecules27051627 - 1 Mar 2022
Cited by 4 | Viewed by 2495
Abstract
We used a grand canonical Monte Carlo simulation to study the influence of impurities including water vapor, SO2, and O2 in the flue gas on the adsorption of CO2/N2 mixture in carbon nanotubes (CNTs) and carboxyl doped [...] Read more.
We used a grand canonical Monte Carlo simulation to study the influence of impurities including water vapor, SO2, and O2 in the flue gas on the adsorption of CO2/N2 mixture in carbon nanotubes (CNTs) and carboxyl doped CNT arrays. In the presence of single impure gas, SO2 yielded the most inhibitions on CO2 adsorption, while the influence of water only occurred at low pressure limit (0.1 bar), where a one-dimensional chain of hydrogen-bonded molecules was formed. Further, O2 was found to hardly affect the adsorption and separation of CO2. With three impurities in flue gas, SO2 still played a major role to suppress the adsorption of CO2 by reducing the adsorption amount significantly. This was mainly because SO2 had a stronger interaction with carbon walls in comparison with CO2. The presence of three impurities in flue gas enhanced the adsorption complexity due to the interactions between different species. Modified by hydrophilic carboxyl groups, a large amount of H2O occupied the adsorption space outside the tube in the carbon nanotube arrays, and SO2 produced competitive adsorption for CO2 in the tube. Both of the two effects inhibited the adsorption of CO2, but improved the selectivity of CO2/N2, and the competition between the two determined the adsorption distribution of CO2 inside and outside the tube. In addition, it was found that (7, 7) CNT always maintained the best CO2/N2 adsorption and separation performance in the presence of impurity gas, for both the cases of single CNT and CNT array. Full article
(This article belongs to the Special Issue Exploration of the Separation Processes in Nanomaterials)
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12 pages, 12752 KiB  
Article
Efficient Estimation of Permeate Flux of Asymmetric Ceramic Membranes for Vacuum Membrane Distillation
by Kaiyun Fu, Yunzhao Guo, Wenbo Qi, Xianfu Chen, Minghui Qiu and Yiqun Fan
Molecules 2022, 27(3), 1057; https://doi.org/10.3390/molecules27031057 - 4 Feb 2022
Cited by 5 | Viewed by 2031
Abstract
Ceramic membranes have the advantages of high mechanical strength and thermal stability and are promising candidates for membrane distillation. Ceramic membranes are generally designed to have a multilayer structure with different pore sizes to create a high liquid entry pressure and obtain a [...] Read more.
Ceramic membranes have the advantages of high mechanical strength and thermal stability and are promising candidates for membrane distillation. Ceramic membranes are generally designed to have a multilayer structure with different pore sizes to create a high liquid entry pressure and obtain a high permeability. However, these structural characteristics pose significant difficulties in predicting permeate flux in a ceramic membrane contactor for vacuum membrane distillation (VMD). Here, a modeling approach was developed to simulate the VMD process and verified by comparing the simulated results with the experimental data. Furthermore, correlations are proposed to simplify the calculations of permeate flux for VMD using asymmetric ceramic membranes by assuming those multilayers to be an effectively quasi-symmetric layer and by introducing a correction factor. The simulation results indicated that this simplified correlation was effective and enabled a quick estimation of the effect of membrane parameters on permeate flux. Full article
(This article belongs to the Special Issue Exploration of the Separation Processes in Nanomaterials)
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