Membranes

2 pages, 634 KiB

Open AccessCorrection

Correction: Zahid et al. Fabrication and Characterization of Sulfonated Graphene Oxide-Doped Polymeric Membranes with Improved Anti-Biofouling Behavior. Membranes 2021, 11, 563

by Muhammad Zahid, Anum Rashid, Saba Akram, H. M. Fayzan Shakir, Zulfiqar Ahmad Rehan, Talha Javed, Rubab Shabbir and Mahmoud M. Hessien

Membranes 2025, 15(5), 131; https://doi.org/10.3390/membranes15050131 - 29 Apr 2025

Abstract

In the original publication [...] Full article

(This article belongs to the Special Issue Microfluidics and MEMS Technology for Membranes)

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16 pages, 4236 KiB

Open AccessArticle

Halloysite-Nanotube-Mediated High-Flux γ-Al₂O₃ Ultrafiltration Membranes for Semiconductor Wastewater Treatment

by Shining Geng, Dazhi Chen, Zhenghua Guo, Qian Li, Manyu Wen, Jiahui Wang, Kaidi Guo, Jing Wang, Yu Wang, Liang Yu, Xinglong Li and Xiaohu Li

Membranes 2025, 15(5), 130; https://doi.org/10.3390/membranes15050130 - 27 Apr 2025

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Abstract

The wastewater from Chemical Mechanical Polishing (CMP) generated in the semiconductor industry contains a significant concentration of suspended particles and necessitates rigorous treatment to meet environmental standards. Ceramic ultrafiltration membranes offer significant advantages in treating such high-solid wastewater, including a high separation efficiency, environmental friendliness, and straightforward cleaning and maintenance. However, the preparation of high-precision ceramic ultrafiltration membranes with a smaller pore size (usually <20 nm) is very complicated, requiring the repeated construction of transition layers, which not only increases the time and economic costs of manufacturing but also leads to an elevated transport resistance. In this work, halloysite nanotubes (HNTs), characterized by their high aspect ratio and lumen structure, were utilized to create a high-porosity transition layer using a spray-coating technique, onto which a γ-Al₂O₃ ultrafiltration selective layer was subsequently coated. Compared to the conventional α-Al₂O₃ transition multilayers, the HNTs-derived transition layer not only had an improved porosity but also had a reduced pore size. As such, this strategy tended to simplify the preparation process for the ceramic membranes while reducing the transport resistance. The resulting high-flux γ-Al₂O₃ ultrafiltration membranes were used for the high-efficiency treatment of CMP wastewater, and the fouling behaviors were investigated. As expected, the HNTs-mediated γ-Al₂O₃ ultrafiltration membranes exhibited excellent water flux (126 LMH) and high rejection (99.4%) of inorganic particles in different solvent systems. In addition, such membranes demonstrated good operation stability and regeneration performance, showing promise for their application in the high-efficiency treatment of CMP wastewater in the semiconductor industry. Full article

(This article belongs to the Section Membrane Applications for Water Treatment)

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13 pages, 2280 KiB

Open AccessArticle

The Enrichment of Acetic Acid Using an Integrated Reverse Osmosis–Electrodialysis Process

by Shichang Xu, Long Zhang, Zhen Zhang, Lixin Xie and Wen Zhang

Membranes 2025, 15(5), 129; https://doi.org/10.3390/membranes15050129 - 27 Apr 2025

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Abstract

In this study, the integrated process of reverse osmosis (RO) and electrodialysis (ED) is developed to concentrate the dilute solution of acetic acid (HAc). The key parameters, such as RO pressure, ED voltage, and ED volume ratio, were systematically evaluated and the operation conditions of the processes were optimized. Under an operating pressure of 5 MPa, RO can enrich low-concentration HAc from 1.5 wt.% to 6.5% wt.% and the energy consumption is 0.37 kW·h·kg⁻¹. Next, RO-concentrated water was used as the ED feed and the first ED with a volume ratio of the concentrated to dilute chamber of 1:4 was carried out under the conditions of a flow rate of 30 L/h and an operating voltage of 12 V; the HAc concentration reached 12.50 wt.%. The second ED with a volume ratio of 1:5 made the final HAc concentration reach 19.02 wt.%. This study shows that using RO-concentrated water instead of initial water for the ED process can reduce water energy consumption and cost markedly, and the RO–ED integrated process can efficiently pre-enrich low-concentration HAc aqueous solution, and the enriched HAc concentration meets the requirements for the further distillation of HAc. Full article

(This article belongs to the Section Membrane Applications for Water Treatment)

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15 pages, 4108 KiB

Open AccessArticle

Improved CO₂/CH₄ Separation in Carbon Molecular Sieve Membranes via Copolymerization of Long-Chain Flexible Structures

by Yingxiu Wu, Haiyan Guo, Bingyu Zhao, Yuxiu Yu, Yaodong Liu and Shouchun Zhang

Membranes 2025, 15(5), 128; https://doi.org/10.3390/membranes15050128 - 27 Apr 2025

Viewed by 163

Abstract

Carbon molecular sieve (CMS) membranes demonstrate considerable advantages and significant potential in the separation of CO₂ and CH₄. Nevertheless, current research predominantly emphasizes the enhancement of CMS membranes through the incorporation of rigid structures and chain spatial stacking. The role of flexible structures in this context remains inadequately understood. To address this gap, we introduced long-chain polydimethylsiloxane (PDMS) and copolymerized it to synthesize polyimide that combines rigid and flexible frameworks. This approach enabled us to investigate the impact of flexible structures on the structure and properties of carbon membranes by varying the PDMS content. The findings indicated that flexible PDMS significantly influenced the thermal decomposition behavior of polyimide and facilitated in situ silicon doping within the carbon membranes, thereby modifying the pore characteristics of the carbon film. Specifically, with a 10% addition of PDMS, the CO₂ permeability of the CMS membrane reached 9556 Barrer, representing an enhancement of 103.9% and surpassing the 2019 upper bound for CO₂/CH₄ separation. Furthermore, the effect of pyrolysis temperature was also examined. Ultimately, this study offers a novel perspective on regulating the structural and performance characteristics of carbon membranes through the integration of long-chain flexible structures. Full article

(This article belongs to the Topic Membrane Separation Technology Research)

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18 pages, 5086 KiB

Open AccessArticle

Addressing Contaminants of Emerging Concern in Aquaculture: A Vacuum Membrane Distillation Approach

by Claudio Marcos Eugênio Malaghini, Jussara Garcez, Rodrigo Hoff, Alan Ambrosi and Katia Rezzadori

Membranes 2025, 15(5), 127; https://doi.org/10.3390/membranes15050127 - 24 Apr 2025

Viewed by 145

Abstract

The presence of contaminants of emerging concern (CECs) in agricultural and fisheries water has raised significant environmental and health concerns. Vacuum membrane distillation (VMD) has shown promise as an effective method for removing non-volatile contaminants, such as CECs, from water. This study presents a novel application of a bench-scale VMD unit to treat water from Lagoa da Conceição, Florianópolis, Brazil, using microporous membranes (0.22 µm) under the following optimized conditions: 75 °C, a flow rate of 24 L·h⁻¹, and a vacuum pressure of −640 mmHg. The system demonstrated remarkable performance in removing several key antimicrobials, including sulfamethoxazole, ciprofloxacin, azithromycin, and clindamycin (500 μg·L⁻¹), with rejection rates of 99.1%, 98%, 99.9%, and 99%, respectively, and an average flux of 7.08 L·m⁻²·h⁻¹. Additionally, the VMD unit achieved a substantial 99.98% salt rejection. Ecotoxicity tests revealed low toxicity for sulfamethoxazole, ciprofloxacin, and azithromycin but high toxicity for clindamycin, while human risk assessment indicated moderate-to-high risks for ciprofloxacin and clindamycin. The findings highlight the potential of VMD as an effective and sustainable technology for the removal of CECs and biocompounds, enhancing water safety and reducing environmental hazards. This study offers a promising solution for addressing water contamination on a broader scale. Full article

(This article belongs to the Section Membrane Applications for Other Areas)

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Membranes, Volume 15, Issue 5 (May 2025) – 5 articles

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