Membranes

33 pages, 7458 KiB

Open AccessArticle

Performance and Environmental Assessment of Biochar-Based Membranes Synthesized from Traditional and Eco-Friendly Solvents

by Abelline Fionah, Isaac Oluk, Laura Brady, Diana M. Byrne and Isabel C. Escobar

Membranes 2024, 14(7), 153; https://doi.org/10.3390/membranes14070153 - 11 Jul 2024

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Abstract

Water contamination resulting from coal spills is one of the largest environmental problems affecting communities in the Appalachia Region of the United States. This coal slurry contains potentially toxic substances, such as hydrocarbons, heavy metals, and coal cleaning chemicals, and its leakage into [...] Read more.

Water contamination resulting from coal spills is one of the largest environmental problems affecting communities in the Appalachia Region of the United States. This coal slurry contains potentially toxic substances, such as hydrocarbons, heavy metals, and coal cleaning chemicals, and its leakage into water bodies (lakes, rivers, and aquifers) can lead to adverse health effects not only for freshwater bodies and plant life but also for humans. This study focused on two major experiments. The first experiment involved the use of biochar to create a biochar–polysulfone (BC-PSf) flat-sheet multifunctional membrane to remove organic contaminants, and the other major experiment compared eco-friendly (gamma-valerolactone—GVL; Rhodiasolv^® PolarClean—PC) and petroleum-derived solvents (i.e., N-methyl-pyrrolidone—NMP) in the fabrication of the biochar–polysulfone membranes. The resulting membranes were tested for their efficiency in removing both positively and negatively charged organic contaminants from the collected water at varying pH values. A comparative life cycle assessment (LCA) with accompanying uncertainty and sensitivity analyses was carried out to understand the global environmental impacts of incorporating biochar, NMP, GVL, and PC in the synthesis of PSf/NMP, BC-PSf/NMP, PSf/GVL, BC-PSf/GVL, PSf/PC, and BC-PSf/PC membranes at a set surface area of 1000 m². The results showed that the addition of biochar to the membrane matrix increased the surface area of the membranes and improved both their adsorptive and mechanical properties. The membranes with biochar incorporated in their matrix showed a higher potential for contaminant removal than those without biochar. The environmental impacts normalized to the BC-PSf/GVL membrane showed that the addition of biochar increased global warming impacts, eutrophication, and respiratory impacts by over 100% in all the membrane configurations with biochar. The environmental impacts were highly sensitive to biochar addition (Spearman’s coefficient > 0.8). The BC/PSf membrane with Rhodiasolv^® PolarClean had the lowest associated global environmental impacts among all the membranes with biochar. Ultimately, this study highlighted potential tradeoffs between functional performance and global environmental impacts regarding choices for membrane fabrication. Full article

(This article belongs to the Collection Polymeric Membranes: Science, Materials and Applications)

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16 pages, 6386 KiB

Open AccessArticle

Fouling Reduction and Thermal Efficiency Enhancement in Membrane Distillation Using a Bilayer-Fluorinated Alkyl Silane–Carbon Nanotube Membrane

by Sumona Paul, Mitun Chandra Bhoumick and Somenath Mitra

Membranes 2024, 14(7), 152; https://doi.org/10.3390/membranes14070152 - 10 Jul 2024

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Abstract

In this study, we report the robust hydrophobicity, lower fouling propensity, and high thermal efficiency of the 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FAS)-coated, carbon nanotube-immobilized membrane (CNIM) when applied to desalination via membrane distillation. Referred to as FAS-CNIM, the membrane was developed through a process that combined [...] Read more.

In this study, we report the robust hydrophobicity, lower fouling propensity, and high thermal efficiency of the 1H,1H,2H,2H-perfluorooctyltriethoxysilane (FAS)-coated, carbon nanotube-immobilized membrane (CNIM) when applied to desalination via membrane distillation. Referred to as FAS-CNIM, the membrane was developed through a process that combined the drop-casting of nanotubes flowed by a dip coating of the FAS layer. The membranes were tested for porosity, surface morphology, thermal stability, contact angle, and flux. The static contact angle of the FAS-CNIM was 153 ± 1°, and the modified membrane showed enhancement in water flux by 18% compared to the base PTFE membrane. The flux was tested at different operating conditions and the fouling behavior was investigated under extreme conditions using a CaCO₃ as well as a mixture of CaCO₃ and CaSO₄ solution. The FAS-CNIM showed significantly lower fouling than plain PTFE or the CNIM; the relative flux reduction was 34.4% and 37.6% lower than the control for the CaCO₃ and CaCO₃/CaSO₄ mixed salt solution. The FAS-CNIM exhibited a notable decrease in specific energy consumption (SEC). Specifically, the SEC for the FAS-CNIM measured 311 kwh/m³ compared to 330.5 kwh/m³ for the CNIM and 354 kwh/m³ for PTFE using a mixture of CaCO₃/CaSO₄. This investigation underscores the significant contribution of the carbon nanotubes’ (CNTs) intermediate layer in creating a durable superhydrophobic membrane, highlighting the potential of utilizing carbon nanotubes for tailored interface engineering to tackle fouling for salt mixtures. The innovative design of a superhydrophobic membrane has the potential to alleviate wetting issues resulting from low surface energy contaminants present in the feed of membrane distillation processes. Full article

(This article belongs to the Special Issue Advances in Porous Hydrophobic Membrane Materials for Membrane Distillation)

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16 pages, 3321 KiB

Open AccessArticle

Cationic Imidazolium-Urethane-Based Poly(Ionic Liquids) Membranes for Enhanced CO₂/CH₄ Separation: Synthesis, Characterization, and Performance Evaluation

by Guilherme Dias, Laura Rocca, Henrique Z. Ferrari, Franciele L. Bernard, Fernando G. Brandão, Leonardo Pereira and Sandra Einloft

Membranes 2024, 14(7), 151; https://doi.org/10.3390/membranes14070151 - 9 Jul 2024

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Abstract

The escalating emissions of CO₂ into the atmosphere require the urgent development of technologies aimed at mitigating environmental impacts. Among these, aqueous amine solutions and polymeric membranes, such as cellulose acetate and polyimide are commercial technologies requiring improvement or substitution to enhance [...] Read more.

The escalating emissions of CO₂ into the atmosphere require the urgent development of technologies aimed at mitigating environmental impacts. Among these, aqueous amine solutions and polymeric membranes, such as cellulose acetate and polyimide are commercial technologies requiring improvement or substitution to enhance the economic and energetic efficiency of CO₂ separation processes. Ionic liquids and poly(ionic liquids) (PILs) are candidates to replace conventional CO₂ separation technologies. PILs are a class of materials capable of combining the favorable gas affinity exhibited by ionic liquids (ILs) with the processability inherent in polymeric materials. In this context, the synthesis of the IL GLYMIM[Cl] was performed, followed by ion exchange processes to achieve GLYMIM variants with diverse counter anions (NTf₂⁻, PF₆⁻, and BF₄). Subsequently, PIL membranes were fabricated from these tailored ILs and subjected to characterization, employing techniques such as SEC, FTIR, DSC, TGA, DMA, FEG-SEM, and CO₂ sorption analysis using the pressure decay method. Furthermore, permeability and ideal selectivity assessments of CO₂/CH₄ mixture were performed to derive the diffusion and solubility coefficients for both CO₂ and CH₄. PIL membranes exhibited adequate thermal and mechanical properties. The PIL-BF₄ demonstrated CO₂ sorption capacities of 33.5 mg CO₂/g at 1 bar and 104.8 mg CO₂/g at 10 bar. Furthermore, the PIL-BF₄ membrane exhibited permeability and ideal (CO₂/CH₄) selectivity values of 41 barrer and 44, respectively, surpassing those of a commercial cellulose acetate membrane as reported in the existing literature. This study underscores the potential of PIL-based membranes as promising candidates for enhanced CO₂ capture technologies. Full article

(This article belongs to the Special Issue Advanced Membrane Materials for CO₂ Capture and Separation)

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13 pages, 2271 KiB

Open AccessArticle

Influence of Iron and Magnesium on Fouling Properties of Organic Matter Solution in Membrane Process

by Mohammad T. Alresheedi

Membranes 2024, 14(7), 150; https://doi.org/10.3390/membranes14070150 - 7 Jul 2024

Viewed by 343

Abstract

Organic matter has been identified as a significant type of foulant in membrane processes for water treatment. Its fouling tendency is highly affected by the presence of ions and inorganics. While the effects of ions addition on organic fouling have been extensively researched [...] Read more.

Organic matter has been identified as a significant type of foulant in membrane processes for water treatment. Its fouling tendency is highly affected by the presence of ions and inorganics. While the effects of ions addition on organic fouling have been extensively researched in the past, studies on the effect of positively-charged inorganics, such as Fe²⁺ and Mg²⁺, on organic fouling are limited. This study investigates the influence of Fe²⁺ and Mg²⁺ addition on fouling properties of the Suwannee River Organic Matter (SROM) solution in the MF process, with and without Ca²⁺ ions. Results showed that increasing the concentration of Fe²⁺ and Mg²⁺ from 0–5 mM promoted SROM fouling, and resulted in an increased flux decline up to 33% and 58%, respectively. Cake layer resistance became more dominant with the addition of Fe²⁺ and Mg²⁺, and was counted for more than 60% of the fouling. Mg²⁺, however, caused higher internal pore blocking, and facilitated the formation of a less permeable cake layer, compared to Fe²⁺. This was evident in the analysis of the cake layer properties and the visualization of the fouling layer. In all cases, SROM fouling with Fe²⁺ and Mg²⁺ worsened with the addition of Ca²⁺ ions. The results of the study indicated the importance of understanding the interaction between organic matter and Fe²⁺ and Mg²⁺, which would provide useful insights on their fouling mechanism and control. Full article

(This article belongs to the Special Issue New Advances in Membrane Fouling during Water and Wastewater Treatment)

13 pages, 3816 KiB

Open AccessArticle

Application of Recycled Ultrafiltration Membranes in an Aerobic Membrane Bioreactor (aMBR): A Validation Study

by Laura Rodríguez-Sáez, Junkal Landaburu-Aguirre, Eloy García-Calvo and Serena Molina

Membranes 2024, 14(7), 149; https://doi.org/10.3390/membranes14070149 - 5 Jul 2024

Viewed by 446

Abstract

A validation study using recycled ultrafiltration membranes (r-UF) on an aerobic membrane bioreactor (aMBR) was conducted for the first time. Four different polyethersulfone (PES) membranes were tested using synthetic urban wastewater (COD 0.4–0.5 g/L) during two experimental periods: (i) recycled ultrafiltration membrane (r-UF) [...] Read more.

A validation study using recycled ultrafiltration membranes (r-UF) on an aerobic membrane bioreactor (aMBR) was conducted for the first time. Four different polyethersulfone (PES) membranes were tested using synthetic urban wastewater (COD 0.4–0.5 g/L) during two experimental periods: (i) recycled ultrafiltration membrane (r-UF) and commercial UF membrane (molecular weight cut-off (MWCO) 150 kDa) (c-150 kDa); (ii) r-UF membrane modified by dip-coating using catechol (CA) and polyethyleneimine (PEI) (mr-UF) and c-20 kDa membrane. Permeability, fouling behavior, and permeate quality were evaluated. Extensive membrane characterization was conducted using scanning electron microscopy (SEM), atomic force microscopy (AFM), energy-dispersive X-ray (EDX), and confocal laser scanning microscopy (CLSM). Permeate quality for r-UF and mr-UF membranes was excellent and comparable to that obtained using commercial membranes under similar conditions. Additionally, r-UF and mr-UF membranes presented a steadier performance time. Additionally, r-UF membrane demonstrated less tendency to be fouled (R_f, m⁻¹) r-UF 7.92 ± 0.57 × 10¹²; mr-UF 9.90 ± 0.14 × 10¹², c-150 kDa 1.56 ± 0.07 × 10¹³ and c-20 kDa 1.25 ± 0.50 × 10¹³. The r-UF membrane showed an excellent antibiofouling character. Therefore, r-UF membranes can be successfully implemented for wastewater treatment in aMBR, being a sustainable and cost-effective alternative to commercial membranes that can contribute to overcome membrane fouling and membrane replacement issues. Full article

(This article belongs to the Special Issue Advanced Membranes and Membrane Technologies for Wastewater Treatment)

34 pages, 8871 KiB

Open AccessReview

Cellulose Membranes: Synthesis and Applications for Water and Gas Separation and Purification

by Jinwu Wang, Syed Comail Abbas, Ling Li, Colleen C. Walker, Yonghao Ni and Zhiyong Cai

Membranes 2024, 14(7), 148; https://doi.org/10.3390/membranes14070148 - 30 Jun 2024

Viewed by 788

Abstract

Membranes are a selective barrier that allows certain species (molecules and ions) to pass through while blocking others. Some rely on size exclusion, where larger molecules get stuck while smaller ones permeate through. Others use differences in charge or polarity to attract and [...] Read more.

Membranes are a selective barrier that allows certain species (molecules and ions) to pass through while blocking others. Some rely on size exclusion, where larger molecules get stuck while smaller ones permeate through. Others use differences in charge or polarity to attract and repel specific species. Membranes can purify air and water by allowing only air and water molecules to pass through, while preventing contaminants such as microorganisms and particles, or to separate a target gas or vapor, such as H₂ and CO₂, from other gases. The higher the flux and selectivity, the better a material is for membranes. The desirable performance can be tuned through material type (polymers, ceramics, and biobased materials), microstructure (porosity and tortuosity), and surface chemistry. Most membranes are made from plastic from petroleum-based resources, contributing to global climate change and plastic pollution. Cellulose can be an alternative sustainable resource for making renewable membranes. Cellulose exists in plant cell walls as natural fibers, which can be broken down into smaller components such as cellulose fibrils, nanofibrils, nanocrystals, and cellulose macromolecules through mechanical and chemical processing. Membranes made from reassembling these particles and molecules have variable pore architecture, porosity, and separation properties and, therefore, have a wide range of applications in nano-, micro-, and ultrafiltration and forward osmosis. Despite their advantages, cellulose membranes face some challenges. Improving the selectivity of membranes for specific molecules often comes at the expense of permeability. The stability of cellulose membranes in harsh environments or under continuous operation needs further improvement. Research is ongoing to address these challenges and develop advanced cellulose membranes with enhanced performance. This article reviews the microstructures, fabrication methods, and potential applications of cellulose membranes, providing some critical insights into processing–structure–property relationships for current state-of-the-art cellulosic membranes that could be used to improve their performance. Full article

(This article belongs to the Special Issue Cellulose Membranes: From Synthesis to Applications)

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25 pages, 9487 KiB

Open AccessArticle

Effects of Varying Spiral-Ring Pitches on CO₂ Absorption by Amine Solution in Concentric Circular Membrane Contactors

by Chii-Dong Ho, Jui-Wei Ke and Jun-Wei Lim

Membranes 2024, 14(7), 147; https://doi.org/10.3390/membranes14070147 - 27 Jun 2024

Viewed by 415

Abstract

The CO₂ absorption flux while using monoethanolamide (MEA) solution in a spiral-wired channel was significantly enhanced by optimizing both the descending and ascending spiral ring pitch configurations within the filled channel. In this study, two distinct spiral ring pitch configurations were integrated [...] Read more.

The CO₂ absorption flux while using monoethanolamide (MEA) solution in a spiral-wired channel was significantly enhanced by optimizing both the descending and ascending spiral ring pitch configurations within the filled channel. In this study, two distinct spiral ring pitch configurations were integrated into concentric circular membrane contactors to augment CO₂ absorption flux. Spiral rods were strategically inserted to mitigate concentration polarization effects, thereby reducing mass transfer boundary layers and increasing turbulence intensity. A theoretical one-dimensional model was developed to predict absorption flux and concentration distributions across varying MEA absorbent flow rates, CO₂ feed flow rates, and inlet CO₂ concentrations in the gas feed. Theoretical predictions of absorption flux improvement were validated against experimental results, demonstrating favorable agreement for both ascending and descending spiral ring pitch operations. Interestingly, the results indicated that descending spiral ring pitch operations achieved higher turbulent intensity compared to ascending configurations, thereby alleviating concentration polarization resistance and enhancing CO₂ absorption flux with reduced polarization effects. Specifically, under conditions of a 40% inlet CO₂ concentration and 5 cm³/s MEA feed flow rate, a notable 83.69% enhancement in absorption flux was achieved compared to using an empty channel configuration. Moreover, a generalized expression for the Sherwood number was derived to predict the mass transfer coefficient for CO₂ absorption in concentric circular membrane contactors, providing a practical tool for performance estimation. The economic feasibility of the spiral-wired module was also assessed by evaluating both absorption flux improvement and incremental power consumption. Overall, these findings underscore the effectiveness of optimizing spiral ring pitch configurations in enhancing CO₂ absorption flux, offering insights into improving the efficiency and economic viability of CO₂ capture technologies. Full article

(This article belongs to the Section Membrane Applications)

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21 pages, 5914 KiB

Open AccessArticle

Removal of Micropollutants in Water Reclamation by Membrane Filtration: Impact of Pretreatments and Adsorption

by Juan C. Aldana, Cristina Agudelo, Pedro M. Álvarez and Juan L. Acero

Membranes 2024, 14(7), 146; https://doi.org/10.3390/membranes14070146 - 27 Jun 2024

Viewed by 411

Abstract

Organic micropollutants (OMPs) present in water and wastewater are in the spotlight because of their potentially harmful effects even at low concentrations and the difficulties of their elimination in urban wastewater treatment plants (UWWTPs). This study explores the impact of some membrane filtration [...] Read more.

Organic micropollutants (OMPs) present in water and wastewater are in the spotlight because of their potentially harmful effects even at low concentrations and the difficulties of their elimination in urban wastewater treatment plants (UWWTPs). This study explores the impact of some membrane filtration processes on the removal of a group of 11 OMPs with an eye on the effects of two pretreatments (i.e., coagulation and adsorption onto powdered activated carbon (PAC)) and the adsorption of OMPs onto the membranes on the overall removal. For this purpose, ultrafiltration (UF) and nanofiltration (NF) experiments were conducted with selected OMPs spiked in ultrapure water and secondary effluents from UWWTPs. It was observed that the adsorption of OMPs onto the membranes was influenced by the characteristics of the membranes, as well as the presence of effluent organic matter (EfOM). Since adsorption was the dominant mechanism for the rejection of OMPs by UF membranes, a study of the adsorption equilibrium of the micropollutants using UF membrane pieces as the adsorbent was conducted. The adsorption isotherms for the most hydrophobic OMPs fitted the Langmuir model. The efficiency of coagulation and powdered activated carbon (PAC) adsorption coupled with UF were also investigated. Both pretreatments alleviated membrane fouling and improved the rejection of organic and inorganic matter. The PAC pretreatment significantly improved the removal of OMPs in the combined PAC/UF process. The best options for achieving reclaimed water with satisfactory physicochemical quality, nearly devoid of OMPs and microorganisms, and suitable for diverse reuse purposes are either the NF treatment or the combination of PAC/UF. Full article

(This article belongs to the Special Issue Advanced Membranes and Membrane Technologies for Wastewater Treatment)

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12 pages, 2623 KiB

Open AccessArticle

Surface Modification of Polyethylene Terephthalate Track-Etched Membranes by 2,2,3,3,4,4,5,5,6,6,7,7-Dodecafluoroheptyl Acrylate for Application in Water Desalination by Direct Contact Membrane Distillation

by Aigerim Kh. Shakayeva, Arman B. Yeszhanov, Alexander N. Borissenko, Murat T. Kassymzhanov, Ainash T. Zhumazhanova, Nikolai A. Khlebnikov, A. K. Nurkassimov, Maxim V. Zdorovets, Olgun Güven and Ilya V. Korolkov

Membranes 2024, 14(7), 145; https://doi.org/10.3390/membranes14070145 - 25 Jun 2024

Viewed by 836

Abstract

In this work, the surfaces of poly (ethylene terephthalate) track-etched membranes (PET TeMs) with pore sizes of 670–1310 nm were hydrophobized with 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate (DFHA) by photoinitiated graft polymerization. Attenuated total reflection FTIR spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) coupled to an energy-dispersive [...] Read more.

In this work, the surfaces of poly (ethylene terephthalate) track-etched membranes (PET TeMs) with pore sizes of 670–1310 nm were hydrophobized with 2,2,3,3,4,4,5,5,6,6,7,7-dodecafluoroheptyl acrylate (DFHA) by photoinitiated graft polymerization. Attenuated total reflection FTIR spectroscopy (ATR-FTIR), scanning electron microscopy (SEM) coupled to an energy-dispersive X-ray spectrometer (EDX), and contact angle measurements were used to identify and characterize the TeMs. The optimal parameters for graft polymerization were determined as follows: polymerization time of 60 min, monomer concentration of 30%, and distance from the UV source of 7 cm. The water contact angle of the modified membranes reached 97°, which is 51° for pristine membranes. The modified membranes were tested for water desalination using direct contact membrane distillation (DCMD) method. The effects of membrane pore size, the degree of grafting, and salt concentration on the performance of membrane distillation process were investigated. According to the results obtained, it has been concluded that large pore size hydrophobic TeMs modified by using DFHA could be used for desalinating water. Full article

(This article belongs to the Section Membrane Applications)

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19 pages, 7137 KiB

Open AccessReview

Bibliometric and Visual Analysis of Studies on Ceramic Membranes: A Review

by Hao Xiong, Xianfu Chen, Jun Feng, Fan Zhang, Minghui Qiu, Qi Zhang and Yiqun Fan

Membranes 2024, 14(7), 144; https://doi.org/10.3390/membranes14070144 - 25 Jun 2024

Viewed by 436

Abstract

As a high-performance separation material, the ceramic membrane has played a crucial role in addressing resource, energy, and environmental challenges. Here, we carried out literature retrieval and collection for the research of ceramic membranes based on the Web of Science. The retrieval strategy [...] Read more.

As a high-performance separation material, the ceramic membrane has played a crucial role in addressing resource, energy, and environmental challenges. Here, we carried out literature retrieval and collection for the research of ceramic membranes based on the Web of Science. The retrieval strategy was quantitatively evaluated from two dimensions: recall and precision. The distributions of publication time, journal, and related subjects were systematically analyzed. With the help of CiteSpace and VOSviewer, the literature was visually analyzed through the co-occurrence map of authors and the cluster network of keywords. The findings indicate a strong correlation between ceramic membrane research and the field of Chemical Engineering. A core group of authors has emerged as prominent contributors in this area of study. Additionally, there is a notable long-tail effect observed in the application of ceramic membranes. Despite their current low-frequency usage and high-volume potential, these applications hold substantial promise for future scientific research and industrial development. Full article

(This article belongs to the Section Inorganic Membranes)

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Membranes, Volume 14, Issue 7 (July 2024) – 10 articles

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