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Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges

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A special issue of Membranes (ISSN 2077-0375). This special issue belongs to the section "Membrane Processing and Engineering".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 29065

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Special Issue Editors

Dr. Xin Li

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Guest Editor

Singapore Membrane Technology Centre, Nanyang Technological University, Singapore 637141, Singapore
Interests: polyelectrolytes; nanofiltration; reverse osmose; nanocomposite membranes; water treatment; water reuse; wastewater treatment
Special Issues, Collections and Topics in MDPI journals

Dr. Shuaifei Zhao

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Guest Editor

Institute for Frontier Materials, Deakin University, Waurn Ponds, VIC 3216, Australia
Interests: membrane separation; desalination, water treatment; gas separation; carbon capture and utilisation; resource recovery
Special Issues, Collections and Topics in MDPI journals

Prof. Dr. Yasin Orooji

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Guest Editor

College of Materials Science and Engineering, Nanjing Forestry University, Nanjing 210037, China
Interests: catalysis; food; membrane applications; sensing; nanocomposite materials & nanobiotechnology

Special Issue Information

Dear Colleagues,

Separation processes play a significant role in industry and daily life due to their three primary functions: concentration, fractionation, and purification. Although effective separation can be achieved by the utilization of traditional separation technologies, such as condensation and crystallization, the accompanying high energy consumption in the actual separation processes cannot be ignored. Membrane processes, which are proven to be a “minus” strategy in addressing energy and environmental challenges, have been widely used in liquid and gas separation. Compared with traditional separation technologies, membrane separation processes are highly advantageous, allowing energy to be saved in the separation of a wide range of mixtures. Meanwhile, considering its smaller carbon footprint, convenient and compact operation and reduced secondary pollution, the membrane process offers great potential for separation and purification.

This Special Issue of Membranes entitled “Membrane processes for liquid and gas separations: Opportunities and challenges” seeks contributions that evaluate the progress of membrane materials/technologies in enhanced separation processes. Relevant topics include, but are not limited to, novel membrane materials, modification techniques and preparation methods for liquid and gas separation. Hybrid membrane processes and simulation investigations as well as industrial case studies in membrane separation will also be considered. Original research papers and reviews on the above topics are additionally welcome.

Dr. Xin Li
Dr. Shuaifei Zhao
Prof. Dr. Yasin Orooji
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. Membranes is an international peer-reviewed open access monthly 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 processes
Water and wastewater treatment
Water reclamation
Gas separation
Carbon capture

Published Papers (9 papers)

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Research

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17 pages, 6672 KiB

Open AccessArticle

Microstructure and Hydrothermal Stability of Microporous Niobia-Silica Membranes: Effect of Niobium Doping Contents

by Jiachen Xia, Jing Yang, Hao Zhang, Yingming Guo and Ruifeng Zhang

Membranes 2022, 12(5), 527; https://doi.org/10.3390/membranes12050527 - 17 May 2022

Viewed by 1489

Abstract

Methyl-modified niobium-doped silica (Nb/SiO₂) materials with various Nb/Si molar ratios (n_Nb) were fabricated using tetraethoxysilane and methyltriethoxysilane as the silica source and niobium pentachloride as the niobium source by the sol–gel method, and the Nb/SiO₂ membranes were prepared thereof by the dip-coating process under an N₂ calcining atmosphere. Their microstructures were characterized and gas permeances tested. The results showed that the niobium element existed in the formation of the Nb-O groups in the Nb/SiO₂ materials. When the niobium doping content and the calcining temperature were large enough, the Nb₂O₅ crystals could be formed in the SiO₂ frameworks. With the increase of n_Nb and calcination temperature, the formed particle sizes increased. The doping of Nb could enhance the H₂/CO₂ and H₂/N₂ permselectivities of SiO₂ membranes. When n_Nb was equal to 0.08, the Nb/SiO₂ membrane achieved a maximal H₂ permeance of 4.83 × 10⁻⁶ mol·m⁻²·Pa⁻¹·s⁻¹ and H₂/CO₂ permselectivity of 15.49 at 200 °C and 0.1 MPa, which also exhibited great hydrothermal stability and thermal reproducibility. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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15 pages, 5259 KiB

Open AccessArticle

MOF-Derived Nanoporous Carbon Incorporated in the Cation Exchange Membrane for Gradient Power Generation

by Xia Sun, Ying Liu, Ruibo Xu and Yongsheng Chen

Membranes 2022, 12(3), 322; https://doi.org/10.3390/membranes12030322 - 14 Mar 2022

Cited by 6 | Viewed by 3290

Abstract

Ion exchange membranes (IEMs), as a part of the reverse electrodialysis (RED) system, play an important role in salinity gradient power (SGP) generation. Structure optimization of IEMs is critical to increase the power production by RED. In this work, metal organic framework (MOF)-derived nanoporous carbons (hollow zeolitic imidazolate framework (ZIF)-derived nanoporous carbons, HZCs) were incorporated in a sulfonated poly (2, 6-dimethyl-1,4-phenylene oxide) (sPPO) membrane to prepare an organic−inorganic nanocomposite cation exchange membrane (CEM). Physicochemical properties, electrochemical properties, and power generation of the synthesized nanocomposite membranes with different HZCs loading were characterized. The results show that the incorporated HZCs could tailor the microstructure of the membrane matrix, providing a superior performance of the nanocomposite membrane. With a HZCs loading of 1.0 wt.%, the nanocomposite membrane possessed the highest permselectivity of 77.61% and the lowest area resistance of 0.42 Ω·cm², along with a super gross power density of 0.45 W/m², which was 87.5% (about 1.87 times) higher than that of the blank sPPO membrane. Therefore, incorporating of an appropriate amount of HZCs in the ion-exchange membrane can improve the performance of the membrane, providing a promising method to increase the power generation of the RED system. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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15 pages, 1984 KiB

Open AccessArticle

Biodegradable Polymeric Membranes for Organic Solvent/Water Pervaporation Applications

by Pao-Yueh Chang, Jane Wang, Si-Yu Li and Shing-Yi Suen

Membranes 2021, 11(12), 970; https://doi.org/10.3390/membranes11120970 - 09 Dec 2021

Cited by 4 | Viewed by 3294

Abstract

Biodegradable polymers are a green alternative to apply as the base membrane materials in versatile processes. In this study, two dense membranes were made from biodegradable PGS (poly(glycerol sebacate)) and APS (poly(1,3-diamino-2-hydroxypropane-co-polyol sebacate)), respectively. The prepared membranes were characterized by FE-SEM, AFM, ATR-FTIR, TGA, DSC, water contact angle, and degree of swelling, in comparison with the PDMS (polydimethylpolysiloxane) membrane. In the pervaporation process for five organic solvent/water systems at 37 °C, both biodegradable membranes exhibited higher separation factors for ethanol/water and acetic acid/water separations, while the PDMS membrane attained better effectiveness in the other three systems. In particular, a positive relationship between the separation factor and the swelling ratio of organic solvent to water (DS_o/DS_w) was noticed. In spite of their biodegradability, the stability of both PGS and APS membranes was not deteriorated on ethanol/water pervaporation for one month. Furthermore, these two biodegradable membranes were applied in the pervaporation of simulated ABE (acetone-butanol-ethanol) fermentation solution, and the results were comparable with those reported in the literature. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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16 pages, 3901 KiB

Open AccessArticle

Construction of Loose Positively Charged NF Membrane by Layer-by-Layer Grafting of Polyphenol and Polyethyleneimine on the PES/Fe Substrate for Dye/Salt Separation

by Shuai Liu, Xiaofeng Fang, Mengmeng Lou, Yihan Qi, Ruo Li, Gang Chen, Yonglian Li, Yanbiao Liu and Fang Li

Membranes 2021, 11(9), 699; https://doi.org/10.3390/membranes11090699 - 13 Sep 2021

Cited by 8 | Viewed by 2950

Abstract

The effective separation of dyes and inorganic salts is highly desirable for recycling inorganic salts and water resource in printing and dyeing wastewater treatment. In this work, tannic acid (TA) and polyethyleneimine (PEI) were grafted on the PES/Fe ultrafiltration membrane via the coordination assembly and Michael addition strategy to fabricated a loose nanofiltration membrane (LNM). The effect of PEI concentration on membrane morphologies and properties was systematically investigated. The membrane surface becomes more hydrophilic and transforms into positive charge after the PEI grafting. The optimized PES/Fe-TA-PEI membrane possesses high pure water flux (124.6 L·m⁻²·h⁻¹) and excellent dye rejections (98.5%, 99.8%, 98.4%, and 86.4% for Congo red, Eriochrome black T, Alcian blue 8GX, and Bromophenol blue, respectively) under 2 bar operation pressure. Meanwhile, the LNM showed a high Alcian blue 8GX rejection (>98.4%) and low NaCl rejection (<5.3%) for the dye/salt mixed solutions separation. Moreover, the PES/Fe-TA-PEI LNM exhibited good antifouling performance and long-term performance stability. These results reveal that such LNM shows great potential for effective fractionation of dyes and salts and recycling of textile wastewater. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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11 pages, 2070 KiB

Open AccessArticle

Effects of High Salinity on Alginate Fouling during Ultrafiltration of High-Salinity Organic Synthetic Wastewater

by Weiwei Cai, Qiuying Chen, Jingyu Zhang, Yan Li, Wenwen Xie and Jingwei Wang

Membranes 2021, 11(8), 590; https://doi.org/10.3390/membranes11080590 - 31 Jul 2021

Cited by 2 | Viewed by 1980

Abstract

Ultrafiltration is widely employed in treating high-salinity organic wastewater for the purpose of retaining particulates, microbes and macromolecules etc. In general, high-salinity wastewater contains diverse types of saline ions at fairly high concentration, which may significantly change foulant properties and subsequent fouling propensity during ultrafiltration. This study filled a knowledge gap by investigating polysaccharide fouling formation affected by various high saline environments, where 2 mol/L Na⁺ and 0.5–1.0 mol/L Ca²⁺/Al³⁺ were employed and the synergistic influences of Na⁺-Ca²⁺ and Na⁺-Al³⁺ were further unveiled. The results demonstrated that the synergistic influence of Na⁺-Ca²⁺ strikingly enlarged the alginate size due to the bridging effects of Ca²⁺ via binding with carboxyl groups in alginate chains. As compared with pure alginate, the involvement of Na⁺ aggravated alginate fouling formation, while the subsequent addition of Ca²⁺ or Al³⁺ on the basis of Na⁺ mitigated fouling development. The coexistence of Na⁺-Ca²⁺ led to alginate fouling formed mostly in a loose and reversible pattern, accompanied by significant cracks appearing on the cake layer. In contrast, the fouling layer formed by alginate-Na⁺-Al³⁺ seemed to be much denser, leading to severer irreversible fouling formation. Notably, the membrane rejection under various high salinity conditions was seriously weakened. Consequently, the current study offered in-depth insights into the development of polysaccharide-associated fouling during ultrafiltration of high-salinity organic wastewater. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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14 pages, 2960 KiB

Open AccessArticle

Biochar/Kevlar Nanofiber Mixed Matrix Nanofiltration Membranes with Enhanced Dye/Salt Separation Performance

by Shiguo Gu, Lei Li, Fei Liu and Jian Li

Membranes 2021, 11(6), 443; https://doi.org/10.3390/membranes11060443 - 12 Jun 2021

Cited by 9 | Viewed by 3148

Abstract

Mixed matrix membranes have received ever-growing attention due to their high separation performance, taking the advantages of both porous fillers and polymer backbones. However, limitations still exist due to the instability of polymers in harsh environments. Here, Kevlar aramid nanofibers, a nanoscale version of poly(paraphenylene terephthalamide), were applied to fabricate a nanofiltration membrane by a thermo-assisted phase inversion method due to their high mechanical strength, physical stability and resistance to solvents. Biochar was incorporated in the Kevlar nanofibers to evaluate its performance in dye/salt separation performance. The fillers’ distribution in the polymeric matrix, structural characteristics, and the interaction of fillers with the polymer in the membrane were characterized via SEM, FTIR, AFM and contact angle analysis. Under the optimal fabrication conditions, the obtained membrane exhibited a pure water flux of 3.83 L m⁻² h⁻¹ bar⁻¹ with a dye rejection of 90.55%, 93.54% and 95.41% for Congo red, methyl blue and Reactive blue 19, respectively. Meanwhile, the mixed matrix membrane maintained a salt rejection of 59.92% and 85.37% for NaCl and Na₂SO₄, respectively. The obtained membrane with high separation performance suggested that Kevlar nanofiber and biochar are good candidates for membrane synthesis. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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15 pages, 41336 KiB

Open AccessArticle

Cation Exchange Membranes Coated with Polyethyleneimine and Crown Ether to Improve Monovalent Cation Electrodialytic Selectivity

by Shanshan Yang, Shuaijun Yu, Lu Yu, Yuanwei Liu, Junbin Liao, Jiangnan Shen and Congjie Gao

Membranes 2021, 11(5), 351; https://doi.org/10.3390/membranes11050351 - 10 May 2021

Cited by 8 | Viewed by 3399

Abstract

Developing monovalent cation permselective membranes (MCPMs) with high-efficient permselectivity is the core concern in specific industrial applications. In this work, we have fabricated a series of novel cation exchange membranes (CEMs) based on sulfonated polysulfone (SPSF) surface modification by polyethyleneimine (PEI) and 4′-aminobenzo-12-crown-4 (12C4) codeposited with dopamine (DA) successively, which was followed by the cross-linking of glutaraldehyde (GA). The as-prepared membranes before and after modification were systematically characterized with regard to their structures as well as their physicochemical and electrochemical properties. Particularly, the codeposition sequence of modified ingredients was investigated on galvanostatic permselectivity to cations. The modified membrane (M-12C4-0.50-PEI) exhibits significantly prominent selectivity to Li⁺ ions (

P_{{Mg}^{2 +}}^{{Li}^{+}}

= 5.23) and K⁺ ions (

P_{{Mg}^{2 +}}^{K^{+}}

= 13.56) in Li⁺/Mg²⁺ and K⁺/Mg²⁺ systems in electrodialysis (ED), which is far superior to the pristine membrane (M-0,

P_{{Mg}^{2 +}}^{{Li}^{+}}

= 0.46,

P_{{Mg}^{2 +}}^{K^{+}}

= 1.23) at a constant current density of 5.0 mA·cm⁻². It possibly arises from the synergistic effects of electrostatic repulsion (positively charged PEI), pore-size sieving (distribution of modified ingredients), and specific interaction effect (12C4 ~Li⁺). This facile strategy may provide new insights into developing selective CEMs in the separation of specific cations by ED. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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11 pages, 43276 KiB

Open AccessArticle

Organic Nanobowls Modified Thin Film Composite Membrane for Enhanced Purification Performance toward Different Water Resources

by Changjin Ou, Sisi Li, Zhongyi Wang, Juan Qin, Qian Wang, Zhipeng Liao and Jiansheng Li

Membranes 2021, 11(5), 350; https://doi.org/10.3390/membranes11050350 - 10 May 2021

Cited by 12 | Viewed by 2490

Abstract

The structure and composition of nanofillers have a significant influence on polyamide nanofiltration (NF) membranes. In this work, an asymmetric organic nanobowl containing a concave cavity was synthesized and incorporated into a polyamide layer to prepare thin film nanocomposite (TFN) membranes via an interfacial polymerization process. Benefiting from the hydrophilicity, hollow cavity and charge property of the compatible organic nanobowls, the separation performance of the developed TFN membrane was significantly improved. The corresponding water fluxes increased to 119.44 ± 5.56, 141.82 ± 3.24 and 130.27 ± 2.05 L/(m²·h) toward Na₂SO₄, MgCl₂ and NaCl solutions, respectively, with higher rejections, compared with the control thin film composite (TFC) and commercial (CM) membranes. Besides this, the modified TFN membrane presented a satisfying purification performance toward tap water, municipal effluent and heavy metal wastewater. More importantly, a better antifouling property of the TFN membrane than TFC and CM membranes was achieved with the assistance of organic nanobowls. These results indicate that the separation performance of the TFN membrane can be elevated by the incorporation of organic nanobowls. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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Review

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21 pages, 4602 KiB

Open AccessReview

Progress in Research and Application of Nanofiltration (NF) Technology for Brackish Water Treatment

by Jiayu Tian, Xingrui Zhao, Shanshan Gao, Xiaoying Wang and Ruijun Zhang

Membranes 2021, 11(9), 662; https://doi.org/10.3390/membranes11090662 - 28 Aug 2021

Cited by 30 | Viewed by 5413

Abstract

Brackish water is a potential fresh water resource with lower salt content than seawater. Desalination of brackish water is an important option to alleviate the prevalent water crisis around the world. As a membrane technology ranging between UF and RO, NF can achieve the partial desalination via size exclusion and charge exclusion. So, it has been widely concerned and applied in treatment of brackish water during the past several decades. Hereon, an overview of the progress in research on and application of NF technology for brackish water treatment is provided. On the basis of expounding the features of brackish water, the factors affecting NF efficiency, including the feed water characteristics, operating conditions and NF membrane properties, are analyzed. For the ubiquitous membrane fouling problem, three preventive fouling control strategies including feed water pretreatment, optimization of operating conditions and selection of anti-fouling membranes are summarized. In addition, membrane cleaning methods for restoring the fouled membrane are discussed. Furthermore, the combined utilization of NF with other membrane technologies is reviewed. Finally, future research prospects are proposed to deal with the current existing problems. Lessons gained from this review are expected to promote the sustainable development of brackish water treatment with NF technology. Full article

(This article belongs to the Special Issue Membrane Processes for Liquid and Gas Separations: Opportunities and Challenges)

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