Membranes

2024

Jump to: 2023, 2022, 2021

33 pages, 7458 KiB

Open AccessEditor’s ChoiceArticle

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

Viewed by 1710

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

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15 pages, 3753 KiB

Open AccessArticle

Removal of Methylene Blue Dye from Aqueous Solutions Using Polymer Inclusion Membrane Containing Calix[4]pyrrole

by Anna Nowik-Zajac, Iwona Zawierucha, Jakub Lagiewka, Karolina Jaksender, Katarzyna Witt, Grzegorz Malina and Vira Sabadash

Membranes 2024, 14(4), 92; https://doi.org/10.3390/membranes14040092 - 17 Apr 2024

Cited by 3 | Viewed by 1799

Abstract

The effective purification of aqueous solutions of methylene blue dye was tested using polymer inclusion membranes (PIMs) that contained cellulose triacetate (CTA) as a polymer base, o-nitrophenyl octyl ether (o-NPOE) as a plasticizer, and meso-tetra methyl tetrakis-[methyl-2-(4-acetlphenoxy)] calix[4]pyrrole (KP) as [...] Read more.

The effective purification of aqueous solutions of methylene blue dye was tested using polymer inclusion membranes (PIMs) that contained cellulose triacetate (CTA) as a polymer base, o-nitrophenyl octyl ether (o-NPOE) as a plasticizer, and meso-tetra methyl tetrakis-[methyl-2-(4-acetlphenoxy)] calix[4]pyrrole (KP) as a carrier. Scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy were used to define the microstructure and surface of PIMs. Experimental results showed that, with an increased concentration of methylene blue in an aqueous solution, the removal percentage also increased. Further observation showed that the flux increased with the rise in the source phase pH values from 3 to 10. The carrier and plasticizer content in the membrane significantly influenced the membrane’s transport properties. The optimal composition of the membrane in percent by weight for KP was 74% plasticizer; 18% support, and 8% carrier. The maximum MB removal (93.10%) was achieved at 0.10 M HCl solution as the receiving phase. It was shown that the membrane with optimal composition showed good reusability and enabled the easy and spontaneous separation of methylene blue from aqueous solutions. Full article

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2023

Jump to: 2024, 2022, 2021

14 pages, 2944 KiB

Open AccessArticle

Single-Pass Tangential Flow Filtration (SPTFF) of Nanoparticles: Achieving Sustainable Operation with Dilute Colloidal Suspensions for Gene Therapy Applications

by Akshay S. Chaubal and Andrew L. Zydney

Membranes 2023, 13(4), 433; https://doi.org/10.3390/membranes13040433 - 15 Apr 2023

Cited by 9 | Viewed by 4400

Abstract

Recent approval of several viral-vector-based therapeutics has led to renewed interest in the development of more efficient bioprocessing strategies for gene therapy products. Single-Pass Tangential Flow Filtration (SPTFF) can potentially provide inline concentration and final formulation of viral vectors with enhanced product quality [...] Read more.

Recent approval of several viral-vector-based therapeutics has led to renewed interest in the development of more efficient bioprocessing strategies for gene therapy products. Single-Pass Tangential Flow Filtration (SPTFF) can potentially provide inline concentration and final formulation of viral vectors with enhanced product quality due. In this study, SPTFF performance was evaluated using a suspension of 100 nm nanoparticles that mimics a typical lentivirus system. Data were obtained with flat-sheet cassettes having 300 kDa nominal molecular weight cutoff, either in full recirculation or single-pass mode. Flux-stepping experiments identified two critical fluxes, one based on boundary-layer particle accumulation (J_bl) and one based on membrane fouling (J_foul). The critical fluxes were well-described using a modified concentration polarization model that captures the observed dependence on feed flow rate and feed concentration. Long-duration filtration experiments were conducted under stable SPTFF conditions, with the results suggesting that sustainable performance could potentially be achieved for as much as 6 weeks of continuous operation. These results provide important insights into the potential application of SPTFF for the concentration of viral vectors in the downstream processing of gene therapy agents. Full article

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2022

Jump to: 2024, 2023, 2021

16 pages, 13149 KiB

Open AccessArticle

Spinning of Polysulfone Hollow Fiber Membranes Using Constant Dope Solution Composition: Viscosity Control via Temperature

by Dmitry Matveev, Ilya Borisov, Vladimir Vasilevsky, Galina Karpacheva and Vladimir Volkov

Membranes 2022, 12(12), 1257; https://doi.org/10.3390/membranes12121257 - 12 Dec 2022

Cited by 21 | Viewed by 3174

Abstract

The dope solution viscosity is an important parameter that largely determines the properties of hollow fiber membranes. In the literature available today, the change in viscosity is carried out only by changing the quantitative and/or qualitative dope solution compositions. However, such an important [...] Read more.

The dope solution viscosity is an important parameter that largely determines the properties of hollow fiber membranes. In the literature available today, the change in viscosity is carried out only by changing the quantitative and/or qualitative dope solution compositions. However, such an important spinning parameter as temperature should significantly affect the dope solution viscosity. For the first time, the influence of the dope solution viscosity of a constant composition on polysulfone hollow fiber membrane properties was studied. The hollow fiber membranes were obtained by the phase separation method induced by a non-solvent (NIPS). The change in the dope solution temperature was carried out in the temperature range of 17–27 °C, providing a dope solution viscosity range of 34.3–21.6 Pa∙s. This work shows that even in such a narrow temperature range, the properties of polysulfone hollow fiber membranes change significantly. With a decrease in the viscosity in this temperature range, the wall thickness of the hollow fiber membrane decreases by 2.8 times; the permeance for the individual gases He and CO₂ increases by 1.6–1.8 times, respectively; the ideal selectivity decreases by 1.12 times; the mean flow pore size increases by 1.63 times; and the surface porosity increases about 3 times. Full article

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22 pages, 6269 KiB

Open AccessArticle

The Development and Study of Some Composite Membranes Based on Polyurethanes and Iron Oxide Nanoparticles

by Luiza Madalina Gradinaru, Stelian Vlad and Romeo Cristian Ciobanu

Membranes 2022, 12(11), 1127; https://doi.org/10.3390/membranes12111127 - 10 Nov 2022

Cited by 3 | Viewed by 2018

Abstract

To improve the performance of composite membranes, their morphology can be tailored by precise control of the fabrication methods and processing conditions. To this end, the aim of this study was to develop novel high-performance composite membranes based on polyurethane matrix and magnetic [...] Read more.

To improve the performance of composite membranes, their morphology can be tailored by precise control of the fabrication methods and processing conditions. To this end, the aim of this study was to develop novel high-performance composite membranes based on polyurethane matrix and magnetic nanoparticles with the desired morphology and stability, by selecting the proper method and fabrication systems. These well-prepared composite membranes were investigated from the point of view of their morphological, physico-chemical, mechanical, dielectric, and magnetic properties. In addition, their in vitro cytocompatibility was also verified by the MTT assay and their cell morphology. The results of this study can provide valuable information regarding the preparation of magnetic polyurethane-based composite membranes that could be used to design some suitable devices with tailored properties, in order to improve the image quality in magnetic resonance imaging investigations and to suppress local image artifacts and blurring. Full article

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14 pages, 4109 KiB

Open AccessArticle

Correlating the Macrostructural Variations of an Ion Gel with Its Carbon Dioxide Sorption Capacity

by Tung Nguyen, Mona Bavarian and Siamak Nejati

Membranes 2022, 12(11), 1087; https://doi.org/10.3390/membranes12111087 - 1 Nov 2022

Viewed by 2058

Abstract

We report on a direct correlation between the macroscale structural variations and the gas sorption capacities of an ion gel. Here, we chose 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([Emim][TF₂N]) and poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) as the ionic liquid and host polymer, respectively. The CO [...] Read more.

We report on a direct correlation between the macroscale structural variations and the gas sorption capacities of an ion gel. Here, we chose 1-ethyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide ([Emim][TF₂N]) and poly(vinylidene fluoride)-co-hexafluoropropylene (PVDF-HFP) as the ionic liquid and host polymer, respectively. The CO₂ sorption in the thin films of the IL-polymer was measured using the gravimetric method. The results of our experiment showed that the trend in CO₂ uptake of these mixtures was nonlinearly correlated with the content of IL. Here, we highlight that the variations in the molecular structure of the polymers were the main reason behind the observed trend. The presented data suggested the possibility of using the composition of mixtures containing IL and polymers to realize a synergistic gain for gas sorption in these mixtures. Full article

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13 pages, 2615 KiB

Open AccessArticle

Performance Comparison of Polymeric and Silica-Based Multi-Bed Pervaporation Membrane Reactors during Ethyl Levulinate Production

by Kamran Ghasemzadeh, Milad Ghahremani, Elham Jalilnejad, Taher Yousefi Amiri and Angelo Basile

Membranes 2022, 12(10), 1000; https://doi.org/10.3390/membranes12101000 - 14 Oct 2022

Cited by 2 | Viewed by 1445

Abstract

A detailed numerical study of ethyl levulinate (EtLA) production with levulinic acid (LA) and ethanol (Et) in a multi-bed traditional reactor (MB-TR) and a silica-based and polymeric multi-bed pervaporation membrane reactors (MB-PVMR) was conducted and the efficiency of each design was studied under [...] Read more.

A detailed numerical study of ethyl levulinate (EtLA) production with levulinic acid (LA) and ethanol (Et) in a multi-bed traditional reactor (MB-TR) and a silica-based and polymeric multi-bed pervaporation membrane reactors (MB-PVMR) was conducted and the efficiency of each design was studied under different operation conditions. Due to water production in the EtLA production process, water removal by a pervaporation system may improve process performance. Our results showed that MB-PVMR had higher performance compared with MB-TR. In addition, the silica membrane was more effective in water removal compared with the polymeric membrane. Therefore, higher LA conversion was achievable by a silica-based multi-bed pervaporation membrane reactor (SMB-PVMR). All the results were evaluated for percentage of water removal and LA conversion, based on variations in the Et/LA molar ratio, feed molar flow, reaction zone temperature, and catalyst loading. The results showed that water removal was higher than 95% and LA conversion of about 95% was attained by SMB-PVMR. Full article

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28 pages, 8734 KiB

Open AccessReview

Hollow Fiber Membrane for Organic Solvent Nanofiltration: A Mini Review

by Liyang Liu, Shaoxiao Liu, Enlin Wang and Baowei Su

Membranes 2022, 12(10), 995; https://doi.org/10.3390/membranes12100995 - 13 Oct 2022

Cited by 6 | Viewed by 4547

Abstract

Organic solvents take up 80% of the total chemicals used in pharmaceutical and related industries, while their reuse rate is less than 50%. Traditional solvent treatment methods such as distillation and evaporation have many disadvantages such as high cost, environmental unfriendliness, and difficulty [...] Read more.

Organic solvents take up 80% of the total chemicals used in pharmaceutical and related industries, while their reuse rate is less than 50%. Traditional solvent treatment methods such as distillation and evaporation have many disadvantages such as high cost, environmental unfriendliness, and difficulty in recovering heat-sensitive, high-value molecules. Organic solvent nanofiltration (OSN) has been a prevalent research topic for the separation and purification of organic solvent systems since the beginning of this century with the benefits of no-phase change, high operational flexibility, low cost, as well as environmental friendliness. Especially, hollow fiber (HF) OSN membranes have gained a lot of attention due to their high packing density and easy scale-up as compared with flat-sheet OSN membranes. This paper critically reviewed the recent research progress in the preparation of HF OSN membranes with high performance, including different materials, preparation methods, and modification treatments. This paper also predicts the future direction of HF OSN membrane development. Full article

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13 pages, 4924 KiB

Open AccessArticle

Electrospun Benzimidazole-Based Polyimide Membrane for Supercapacitor Applications

by Yu-Hsiang Lu, Yen-Zen Wang, Ming-Ying Tsai, Hong-Ping Lin and Chun-Han Hsu

Membranes 2022, 12(10), 961; https://doi.org/10.3390/membranes12100961 - 30 Sep 2022

Cited by 6 | Viewed by 2269

Abstract

A benzimidazole-containing diamine monomer was prepared via a simple one-step synthesis process. A two-step procedure involving polycondensation in the presence of aromatic dianhydrides (4,4′-oxydiphthalic anhydride, ODPA) followed by thermal imidization was then performed to prepare a benzimidazole-based polyimide (BI-PI). BI-PI membranes were fabricated [...] Read more.

A benzimidazole-containing diamine monomer was prepared via a simple one-step synthesis process. A two-step procedure involving polycondensation in the presence of aromatic dianhydrides (4,4′-oxydiphthalic anhydride, ODPA) followed by thermal imidization was then performed to prepare a benzimidazole-based polyimide (BI-PI). BI-PI membranes were fabricated using an electrospinning technique and were hot pressed for 30 min at 200 °C under a pressure of 50 kgf /cm². Finally, the hot-pressed membranes were assembled into supercapacitors, utilizing high-porosity-activated water chestnut shell biochar as the active material. The TGA results showed that the BI-PI polymer produced in the two-step synthesis process had a high thermal stability (T_d5% = 527 °C). Moreover, the hot-press process reduced the pore size in the BI-PI membrane and improved the pore-size uniformity. The hot-press procedure additionally improved the mechanical properties of the BI-PI membrane, resulting in a high tensile modulus of 783 MPa and a tensile strength of 34.8 MPa. The cyclic voltammetry test results showed that the membrane had a specific capacitance of 121 F/g and a capacitance retention of 77%. By contrast, a commercial cellulose separator showed a specific capacitance value of 107 F/g and a capacitance retention of 49% under the same scanning conditions. Finally, the membrane showed both a small equivalent series resistance (R_s) and a small interfacial resistance (R_ct). Overall, the results showed that the BI-PI membrane has significant potential as a separator for high-performance supercapacitor applications. Full article

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21 pages, 20559 KiB

Open AccessArticle

Effect of Temperature and Humidity on the Water and Dioxygen Transport Properties of Polybutylene Succinate/Graphene Nanoplatelets Nanocomposite Films

by Raphaël Cosquer, Sébastien Pruvost and Fabrice Gouanvé

Membranes 2022, 12(7), 721; https://doi.org/10.3390/membranes12070721 - 20 Jul 2022

Cited by 1 | Viewed by 1832

Abstract

Nanocomposite films of polybutylene succinate (PBS)/graphene nanoplatelets (GnP) with a GnP content ranging from 0 to 1.35 wt.% were prepared by melt processing. The morphology of both the neat PBS and PBS/GnP nanocomposites were investigated and revealed no significant impact of GnP on [...] Read more.

Nanocomposite films of polybutylene succinate (PBS)/graphene nanoplatelets (GnP) with a GnP content ranging from 0 to 1.35 wt.% were prepared by melt processing. The morphology of both the neat PBS and PBS/GnP nanocomposites were investigated and revealed no significant impact of GnP on the crystalline microstructure. Moisture sorption at 10 °C, 25 °C, and 40 °C were analyzed and modeled using the Guggenheim, Andersen, and De Boer (GAB) equation and Zimm-Lundberg theory, allowing for a phenomenological analysis at the molecular scale. An understanding of the transport sorption properties was proposed by the determination of the molar heat of sorption (ΔH_s), and the activation energy of the diffusion (E_d) of water in the matrix since both solubility and diffusion are thermo-activable properties. Both ΔH_s and E_d showed a good correlation with the water clustering theory at high water activity. Water and dioxygen permeabilities ( and ) were determined as a function of temperature and water activity. and decreased with the addition of a small amount of GnP, regardless of the studied temperature. Moreover, the evolution of as a function of water activity was driven by the solubility process, whereas at a given water activity, was driven by the diffusion process. Activation energies of the permeability (E_p) of water and dioxygen showed a dependency on the nature of the permeant molecule. Finally, from the ΔH_s, E_d, and E_p obtained values, the reduction in water permeability with the addition of a low content of GnP was attributed mainly to a tortuosity effect without diffusive interfaces rather than a significant change in the transport property mechanism. Full article

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20 pages, 9471 KiB

Open AccessArticle

A Study of the Mechanism and Separation of Structurally Similar Phenolic Acids by Commercial Polymeric Ultrafiltration Membranes

by Qinshi Wang, Yun Zhang, Xianli Zhang, Qi Li, Mingcong Huang, Shasha Huang, Qianlian Wu, Zhishu Tang, Linmei Pan, Yue Zhang, Hongbo Liu, Bo Li and Huaxu Zhu

Membranes 2022, 12(3), 285; https://doi.org/10.3390/membranes12030285 - 1 Mar 2022

Cited by 11 | Viewed by 3438

Abstract

This study examined the behavior and penetration mechanisms of typical phenolic (benzoic) acids, which determine their observed penetration rates during membrane separation, focusing on the influence of electrostatic and hydrophobic solute/membrane interactions. To understand the effects of hydrophobicity and electrostatic interaction on membrane [...] Read more.

This study examined the behavior and penetration mechanisms of typical phenolic (benzoic) acids, which determine their observed penetration rates during membrane separation, focusing on the influence of electrostatic and hydrophobic solute/membrane interactions. To understand the effects of hydrophobicity and electrostatic interaction on membrane filtration, the observed penetration of five structurally similar phenolic acids was compared with regenerated cellulose (RC) and polyamide (PA) membranes at different solute concentrations and solution pHs. Variation partitioning analysis (VPA) was performed to calculate the relative contributions of electrostatic and hydrophobic effects. The penetration of phenolic acids was mainly influenced by the electrostatic interaction, with salicylic acid having the highest penetration. Penetration of phenolic acids through the PA membrane decreased from 98% at pH 3.0 to 30–50% at pH 7.4, indicating the dominance of the electrostatic interaction. Moreover, based on its hydrophobicity and greater surface charge, the PA membrane could separate binary mixtures of protocatechuic/salicylic acid and 4-hydroxybenzoic/salicylic acid at pH 9.0, with separation factors of 1.81 and 1.78, respectively. These results provide a greater understanding of solute/membrane interactions and their effect on the penetration of phenolic acids through polymeric ultrafiltration membranes. Full article

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19 pages, 8795 KiB

Open AccessArticle

On the Potential of a Poly(vinylidenefluoride-co-hexafluoropropylene) Polymer Inclusion Membrane Containing Aliquat^® 336 and Dibutyl Phthalate for V(V) Extraction from Sulfate Solutions

by Salar Bahrami, Leila Dolatyari, Hassan Shayani-Jam, Mohammad Reza Yaftian and Spas D. Kolev

Membranes 2022, 12(1), 90; https://doi.org/10.3390/membranes12010090 - 14 Jan 2022

Cited by 16 | Viewed by 2565

Abstract

A polymer inclusion membrane (PIM) composed of 50 wt% base polymer poly(vinylidenefluoride-co-hexafluoropropylene), 40 wt% extractant Aliquat^® 336, and 10 wt% dibutyl phthalate as plasticizer/modifier provided the efficient extraction of vanadium(V) (initial concentration 50 mg L⁻¹) from 0.1 M [...] Read more.

A polymer inclusion membrane (PIM) composed of 50 wt% base polymer poly(vinylidenefluoride-co-hexafluoropropylene), 40 wt% extractant Aliquat^® 336, and 10 wt% dibutyl phthalate as plasticizer/modifier provided the efficient extraction of vanadium(V) (initial concentration 50 mg L⁻¹) from 0.1 M sulfate solutions (pH 2.5). The average mass and thickness of the PIMs (diameter 3.5 cm) were 0.057 g and 46 μm, respectively. It was suggested that V(V) was extracted as VO₂SO₄⁻ via an anion exchange mechanism. The maximum PIM capacity was estimated to be ~56 mg of V(V)/g for the PIM. Quantitative back-extraction was achieved with a 50 mL solution of 6 M H₂SO₄/1 v/v% of H₂O₂. It was assumed that the back-extraction process involved the oxidation of VO₂⁺ to VO(O₂)⁺ by H₂O₂. The newly developed PIM, with the optimized composition mentioned above, exhibited an excellent selectivity for V(V) in the presence of metallic species present in digests of spent alumina hydrodesulfurization catalysts. Co-extraction of Mo(VI) with V(V) was eliminated by its selective extraction at pH 1.1. Characterization of the optimized PIM was performed by contact angle measurements, atomic-force microscopy, energy dispersive X-ray spectroscopy, thermogravimetric analysis/derivatives thermogravimetric analysis and stress–strain measurements. Replacement of dibutyl phthalate with 2-nitrophenyloctyl ether improved the stability of the studied PIMs. Full article

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2021

Jump to: 2024, 2023, 2022

24 pages, 56152 KiB

Open AccessEditor’s ChoiceArticle

Novel Mixed Matrix Membranes Based on Polymer of Intrinsic Microporosity PIM-1 Modified with Metal-Organic Frameworks for Removal of Heavy Metal Ions and Food Dyes by Nanofiltration

by Anna Kuzminova, Mariia Dmitrenko, Andrey Zolotarev, Aleksandra Korniak, Daria Poloneeva, Artem Selyutin, Alexei Emeline, Alexey Yushkin, Andrew Foster, Peter Budd and Sergey Ermakov

Membranes 2022, 12(1), 14; https://doi.org/10.3390/membranes12010014 - 23 Dec 2021

Cited by 20 | Viewed by 4683

Abstract

Nowadays, nanofiltration is widely used for water treatment due to its advantages, such as energy-saving, sustainability, high efficiency, and compact equipment. In the present work, novel nanofiltration membranes based on the polymer of intrinsic microporosity PIM-1 modified by metal-organic frameworks (MOFs)—MIL-140A and MIL-125—were [...] Read more.

Nowadays, nanofiltration is widely used for water treatment due to its advantages, such as energy-saving, sustainability, high efficiency, and compact equipment. In the present work, novel nanofiltration membranes based on the polymer of intrinsic microporosity PIM-1 modified by metal-organic frameworks (MOFs)—MIL-140A and MIL-125—were developed to increase nanofiltration efficiency for the removal of heavy metal ions and dyes. The structural and physicochemical properties of the developed PIM-1 and PIM-1/MOFs membranes were studied by the spectroscopic technique (FTIR), microscopic methods (SEM and AFM), and contact angle measurement. Transport properties of the developed PIM-1 and PIM-1/MOFs membranes were evaluated in the nanofiltration of the model and real mixtures containing food dyes and heavy metal ions. It was found that the introduction of MOFs (MIL-140A and MIL-125) led to an increase in membrane permeability. It was demonstrated that the membranes could be used to remove and concentrate the food dyes and heavy metal ions from model and real mixtures. Full article

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13 pages, 5077 KiB

Open AccessEditor’s ChoiceArticle

Nanofibrous Membrane with Encapsulated Glucose Oxidase for Self-Sustained Antimicrobial Applications

by Fernaldy Leonarta and Cheng-Kang Lee

Membranes 2021, 11(12), 997; https://doi.org/10.3390/membranes11120997 - 20 Dec 2021

Cited by 8 | Viewed by 3394

Abstract

Polyvinyl alcohol (PVA) nanofibrous membrane, consisting of separately encapsulated glucose oxidase (GOx) and glucose (Glu) nanofibers, was prepared via simultaneously electrospinning PVA/GOx and PVA/Glu dopes. The as-prepared pristine membrane could self-sustainably generate hydrogen peroxide (H₂O₂) only in contact with [...] Read more.

Polyvinyl alcohol (PVA) nanofibrous membrane, consisting of separately encapsulated glucose oxidase (GOx) and glucose (Glu) nanofibers, was prepared via simultaneously electrospinning PVA/GOx and PVA/Glu dopes. The as-prepared pristine membrane could self-sustainably generate hydrogen peroxide (H₂O₂) only in contact with an aqueous solution. The H₂O₂ production level was well maintained even after storing the dry membrane at room temperature for 7 days. Cross-linking the membrane via reaction with glutaraldehyde (GA) vapor could not only prevent the nanofibrous membrane from dissolving in water but also prolonged the release of H₂O₂. The sustained release of H₂O₂ from the membrane achieved antimicrobial capability equivalent to that of 1% H₂O₂ against both Escherichia coli and Staphylococcus aureus. Gram(+) S. aureus cells were more susceptible to H₂O₂ than Gram(−) E. coli and >99% of S. aureus were killed after 1 h incubation with the membrane. Pristine and GA-crosslinked nanofibrous membrane with in situ production of H₂O₂ were self-sterilized in which no microorganism contamination on the membrane could be detected after 2 weeks incubation on an agar plate. The GOx/Glu membrane may find potential application as versatile antimicrobial materials in the field of biomedicine, in the food and health industries, and especially challenges related to wound healing in diabetic patients. Full article

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11 pages, 3940 KiB

Open AccessEditor’s ChoiceArticle

Effect of Nanopatterning on Concentration Polarization during Nanofiltration

by Lauren M. Ward, Barbara G. Fickling and Steven T. Weinman

Membranes 2021, 11(12), 961; https://doi.org/10.3390/membranes11120961 - 7 Dec 2021

Cited by 15 | Viewed by 4169

Abstract

Membranes used for desalination still face challenges during operation. One of these challenges is the buildup of salt ions at the membrane surface. This is known as concentration polarization, and it has a negative effect on membrane water permeance and salt rejection. In [...] Read more.

Membranes used for desalination still face challenges during operation. One of these challenges is the buildup of salt ions at the membrane surface. This is known as concentration polarization, and it has a negative effect on membrane water permeance and salt rejection. In an attempt to decrease concentration polarization, a line-and-groove nanopattern was applied to a nanofiltration (NF) membrane. Aqueous sodium sulfate (Na₂SO₄) solutions were used to test the rejection and permeance of both pristine and patterned membranes. It was found that the nanopatterns did not reduce but increased the concentration polarization at the membrane surface. Based on these studies, different pattern shapes and sizes should be investigated to gain a fundamental understanding of the influence of pattern size and shape on concentration polarization. Full article

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8 pages, 5276 KiB

Open AccessCommunication

From Inner Topological Structure to Functional Nanofibers: Theoretical Analysis and Experimental Verification

by Dan Tian and Chunhui He

Membranes 2021, 11(11), 870; https://doi.org/10.3390/membranes11110870 - 12 Nov 2021

Cited by 6 | Viewed by 1676

Abstract

The mechanical strength of spider silk is the highest among all natural fibers, and its flexibility is also excellent; this phenomenon can be explained geometrically, due to its hierarchical structure, the last cascade of which beginning with well-ordered macromolecules. The inner topological structure [...] Read more.

The mechanical strength of spider silk is the highest among all natural fibers, and its flexibility is also excellent; this phenomenon can be explained geometrically, due to its hierarchical structure, the last cascade of which beginning with well-ordered macromolecules. The inner topological structure of a nanofiber plays an important role in controlling its functions, e.g., its mechanical, electrical and chemical properties. This paper shows that nanoparticles can be well-ordered in the electrospinning process as a result, the nanofibers’ properties can be adjusted. Some experiments are designed to verify our theoretical prediction. Full article

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12 pages, 2142 KiB

Open AccessArticle

Solvent and pH Stability of Poly(styrene-alt-maleic acid) (PSaMA) Membranes Prepared by Aqueous Phase Separation (APS)

by Wouter M. Nielen, Joshua D. Willott and Wiebe M. de Vos

Membranes 2021, 11(11), 835; https://doi.org/10.3390/membranes11110835 - 29 Oct 2021

Cited by 2 | Viewed by 2767

Abstract

In the single-polyelectrolyte aqueous phase separation (APS) approach, membranes are prepared by precipitating a weak polyelectrolyte from a concentrated aqueous solution using a pH switch. This has proven to be a versatile and more sustainable method compared to conventional approaches as it significantly [...] Read more.

In the single-polyelectrolyte aqueous phase separation (APS) approach, membranes are prepared by precipitating a weak polyelectrolyte from a concentrated aqueous solution using a pH switch. This has proven to be a versatile and more sustainable method compared to conventional approaches as it significantly reduces the use of organic solvents. Poly(styrene-alt-maleic acid) (PSaMA) is a polymer that has been extensively investigated for APS and has been the basis for both open and dense membranes with good performances. These membranes are chemically crosslinked and, in this work, we further investigated ultrafiltration (UF) and nanofiltration (NF) membranes prepared with PSaMA for their stability in various organic solvents and under different pH conditions. It was shown that these membranes had stable performances in both isopropanol (IPA) and toluene, and a slightly reduced performance in N-methyl-2-pyrollidone (NMP). However, PSaMA did not perform well as a selective layer in these solvents, indicating that the real opportunity would be to use the UF-type PSaMA membranes as solvent-stable support membranes. Additionally, the membranes proved to be stable in an acidic-to-neutral pH regime (pH 2–7); and, due to the pH-responsive nature of PSaMA, for the NF membranes, a pH-dependent retention of Mg²⁺ and SO₄²⁻ ions was observed and, for the UF membranes, a strong responsive behavior was observed, where the pH can be used to control the membrane permeability. However, long-term exposure to elevated pH conditions (pH 8–10) resulted in severe swelling of the NF membranes, resulting in defect formation, and compaction of the UF membranes. For the UF membranes, this compaction did prove to be reversible for some but not all of the membrane samples measured. These results showed that in aqueous systems, membranes prepared with PSaMA had interesting responsive behaviors but performed best at neutral and acidic pH values. Moreover, the membranes exhibited excellent stability in the organic solvents IPA and toluene Full article

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28 pages, 11978 KiB

Open AccessArticle

Reactional Processes on Osmium–Polymeric Membranes for 5–Nitrobenzimidazole Reduction

by Aurelia Cristina Nechifor, Alexandru Goran, Vlad-Alexandru Grosu, Andreia Pîrțac, Paul Constantin Albu, Ovidiu Oprea, Alexandra Raluca Grosu, Dumitru Pașcu, Florentina Mihaela Păncescu, Gheorghe Nechifor, Szidonia-Katalin Tanczos and Simona Gabriela Bungău

Membranes 2021, 11(8), 633; https://doi.org/10.3390/membranes11080633 - 17 Aug 2021

Cited by 7 | Viewed by 3249

Abstract

Membranes are associated with the efficient processes of separation, concentration and purification, but a very important aspect of them is the realization of a reaction process simultaneously with the separation process. From a practical point of view, chemical reactions have been introduced in [...] Read more.

Membranes are associated with the efficient processes of separation, concentration and purification, but a very important aspect of them is the realization of a reaction process simultaneously with the separation process. From a practical point of view, chemical reactions have been introduced in most membrane systems: with on-liquid membranes, with inorganic membranes or with polymeric and/or composite membranes. This paper presents the obtaining of polymeric membranes containing metallic osmium obtained in situ. Cellulose acetate (CA), polysulfone (PSf) and polypropylene hollow fiber membranes (PPM) were used as support polymer membranes. The metallic osmium is obtained directly onto the considered membranes using a solution of osmium tetroxide (OsO4), dissolved in tert–butyl alcohol (t–Bu–OH) by reduction with molecular hydrogen. The composite osmium–polymer (Os–P)-obtained membranes were characterized in terms of the morphological and structural points of view: scanning electron microscopy (SEM), high-resolution SEM (HR–SEM), energy-dispersive spectroscopy analysis (EDAX), Fourier Transform Infra-Red (FTIR) spectroscopy, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The process performance was tested for reduction of 5–nitrobenzimidazole to 5–aminobenzimidazole with molecular hydrogen. The paper presents the main aspects of the possible mechanism of transformation of 5–nitrobenzimidazole to 5–aminobenzimidazole with hydrogen gas in the reaction system with osmium–polymer membrane (Os–P). Full article

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15 pages, 1160 KiB

Open AccessArticle

Proton Conductive, Low Methanol Crossover Cellulose-Based Membranes

by Jamaliah Aburabie, Boor Lalia and Raed Hashaikeh

Membranes 2021, 11(7), 539; https://doi.org/10.3390/membranes11070539 - 16 Jul 2021

Cited by 16 | Viewed by 3689

Abstract

This work describes the development of sulfated cellulose (SC) polymer and explores its potential as an electrolyte-membrane for direct methanol fuel cells (DMFC). The fabrication of our membranes was initiated by the preparation of the novel sulfated cellulose solution via controlled acid hydrolysis [...] Read more.

This work describes the development of sulfated cellulose (SC) polymer and explores its potential as an electrolyte-membrane for direct methanol fuel cells (DMFC). The fabrication of our membranes was initiated by the preparation of the novel sulfated cellulose solution via controlled acid hydrolysis of microcrystalline cellulose (MCC). Ion-conductive crosslinked SC membranes were prepared following a chemical crosslinking reaction. SC solution was chemically crosslinked with glutaraldehyde (GA) and cured at 30 °C to produce the aforementioned membranes. Effects of GA concentration on methanol permeability, proton conductivity, water uptake and thermal stabilities were investigated. The crosslinking reaction is confirmed by FTIR technique where a bond between the primary OH groups of cellulose and the GA aldehyde groups was achieved, leading to the increased hydrophobic backbone domains in the membrane. The results show that the time of crosslinking reaction highly affects the proton conduction and methanol permeability. The proton conductivity and methanol crossover (3M) of our GA crosslinked SC membranes are 3.7 × 10⁻² mS cm⁻¹ and 8.2 × 10⁻⁹ cm² s⁻¹, respectively. Crosslinked sulfated cellulose films have lower ion conductivity than the state-of-the-art Nafion (10.2 mS cm⁻¹); however, the methanol crossover is three orders of magnitude lower than Nafion membranes (1.0 × 10⁻⁵ cm² s⁻¹ at 1 M). Such biofilms with high methanol resistivity address the major hurdle that prevents the widespread applications of direct alcohol fuel cells. Full article

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16 pages, 3565 KiB

Open AccessEditor’s ChoiceArticle

Green Synthesized of Ag/Ag₂O Nanoparticles Using Aqueous Leaves Extracts of Phoenix dactylifera L. and Their Azo Dye Photodegradation

by Salah Eddine Laouini, Abderrhmane Bouafia, Alexander V. Soldatov, Hamed Algarni, Mohammed Laid Tedjani, Gomaa A. M. Ali and Ahmed Barhoum

Membranes 2021, 11(7), 468; https://doi.org/10.3390/membranes11070468 - 25 Jun 2021

Cited by 91 | Viewed by 6262

Abstract

In this study, silver/silver oxide nanoparticles (Ag/Ag₂O NPs) were successfully biosynthesized using Phoenix dactylifera L. aqueous leaves extract. The effect of different plant extract/precursor contractions (volume ratio, v/v%) on Ag/Ag₂O NP formation, their optical properties, and [...] Read more.

In this study, silver/silver oxide nanoparticles (Ag/Ag₂O NPs) were successfully biosynthesized using Phoenix dactylifera L. aqueous leaves extract. The effect of different plant extract/precursor contractions (volume ratio, v/v%) on Ag/Ag₂O NP formation, their optical properties, and photocatalytic activity towards azo dye degradation, i.e., Congo red (CR) and methylene blue (MB), were investigated. X-ray diffraction confirmed the crystalline nature of Ag/Ag₂O NPs with a crystallite size range from 28 to 39 nm. Scanning electron microscope images showed that the Ag/Ag₂O NPs have an oval and spherical shape. UV–vis spectroscopy showed that Ag/Ag₂O NPs have a direct bandgap of 2.07–2.86 eV and an indirect bandgap of 1.60–1.76 eV. Fourier transform infrared analysis suggests that the synthesized Ag/Ag₂O NPs might be stabilized through the interactions of -OH and C=O groups in the carbohydrates, flavonoids, tannins, and phenolic acids present in Phoenix dactylifera L. Interestingly, the prepared Ag/Ag₂O NPs showed high catalytic degradation activity for CR dye. The photocatalytic degradation of the azo dye was monitored spectrophotometrically in a wavelength range of 250–900 nm, and a high decolorization efficiency (84.50%) was obtained after 50 min of reaction. As a result, the use of Phoenix dactylifera L. aqueous leaves extract offers a cost-effective and eco-friendly method. Full article

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20 pages, 7982 KiB

Open AccessArticle

Improving the Performance of Composite Hollow Fiber Membranes with Magnetic Field Generated Convection Application on pH Correction

by Aurelia Cristina Nechifor, Alexandru Goran, Vlad-Alexandru Grosu, Constantin Bungău, Paul Constantin Albu, Alexandra Raluca Grosu, Ovidiu Oprea, Florentina Mihaela Păncescu and Gheorghe Nechifor

Membranes 2021, 11(6), 445; https://doi.org/10.3390/membranes11060445 - 15 Jun 2021

Cited by 20 | Viewed by 3316

Abstract

The membranes and membrane processes have succeeded in the transition from major technological and biomedical applications to domestic applications: water recycling in washing machines, recycling of used cooking oil, recovery of gasoline vapors in the pumping stations or enrichment of air with oxygen. [...] Read more.

The membranes and membrane processes have succeeded in the transition from major technological and biomedical applications to domestic applications: water recycling in washing machines, recycling of used cooking oil, recovery of gasoline vapors in the pumping stations or enrichment of air with oxygen. In this paper, the neutralization of condensation water and the retention of aluminum from thermal power plants is studied using ethylene propylene diene monomer sulfonated (EPDM-S) membranes containing magnetic particles impregnated in a microporous propylene hollow fiber (I-PPM) matrix. The obtained membranes were characterized from the morphological and structural points of view, using scanning electron microscopy (SEM), high resolution SEM (HR-SEM), energy dispersive spectroscopy analysis (EDAX) and thermal gravimetric analyzer. The process performances (flow, selectivity) were studied using a variable magnetic field generated by electric coils. The results show the possibility of correcting the pH and removing aluminum ions from the condensation water of heating plants, during a winter period, without the intervention of any operator for the maintenance of the process. The pH was raised from an acidic one (2–4), to a slightly basic one (8–8.5), and the concentration of aluminum ions was lowered to the level allowed for discharge. Magnetic convection of the permeation module improves the pH correction process, but especially prevents the deposition of aluminum hydroxide on hollow fibers membranes. Full article

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20 pages, 6098 KiB

Open AccessArticle

Analysis of Polyvinylidene Fluoride Membranes Fabricated for Membrane Distillation

by Minchul Ahn, Hyeongrak Cho, Yongjun Choi, Seockheon Lee and Sangho Lee

Membranes 2021, 11(6), 437; https://doi.org/10.3390/membranes11060437 - 10 Jun 2021

Cited by 1 | Viewed by 3037

Abstract

The optimization of the properties for MD membranes is challenging due to the trade-off between water productivity and wetting tendency. Herein, this study presents a novel methodology to examine the properties of MD membranes. Seven polyvinylidene fluoride (PVDF) membranes were synthesized under different [...] Read more.

The optimization of the properties for MD membranes is challenging due to the trade-off between water productivity and wetting tendency. Herein, this study presents a novel methodology to examine the properties of MD membranes. Seven polyvinylidene fluoride (PVDF) membranes were synthesized under different conditions by the phase inversion method and characterized to measure flux, rejection, contact angle (CA), liquid entry pressure (LEP), and pore sizes. Then, water vapor permeability (B_w), salt leakage ratio (L_w), and fiber radius (R_f) were calculated for the in-depth analysis. Results showed that the water vapor permeability and salt leakage ratio of the prepared membranes ranged from 7.76 × 10⁻⁸ s/m to 20.19 × 10⁻⁸ s/m and from 0.0020 to 0.0151, respectively. The R_f calculated using the Purcell model was in the range from 0.598 μm to 1.690 μm. Since the R_f was relatively small, the prepared membranes can have high LEP (more than 1.13 bar) even at low CA (less than 90.8°). The trade-off relations between the water vapor permeability and the other properties could be confirmed from the results of the prepared membranes. Based on these results, the properties of an efficient MD membrane were suggested as a guideline for the membrane development. Full article

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24 pages, 12151 KiB

Open AccessArticle

Recuperative Amino Acids Separation through Cellulose Derivative Membranes with Microporous Polypropylene Fiber Matrix

by Aurelia Cristina Nechifor, Andreia Pîrțac, Paul Constantin Albu, Alexandra Raluca Grosu, Florina Dumitru, Ioana Alina Dimulescu (Nica), Ovidiu Oprea, Dumitru Pașcu, Gheorghe Nechifor and Simona Gabriela Bungău

Membranes 2021, 11(6), 429; https://doi.org/10.3390/membranes11060429 - 5 Jun 2021

Cited by 20 | Viewed by 4532

Abstract

The separation, concentration and transport of the amino acids through membranes have been continuously developed due to the multitude of interest amino acids of interest and the sources from which they must be recovered. At the same time, the types of membranes used [...] Read more.

The separation, concentration and transport of the amino acids through membranes have been continuously developed due to the multitude of interest amino acids of interest and the sources from which they must be recovered. At the same time, the types of membranes used in the sepa-ration of the amino acids are the most diverse: liquids, ion exchangers, inorganic, polymeric or composites. This paper addresses the recuperative separation of three amino acids (alanine, phe-nylalanine, and methionine) using membranes from cellulosic derivatives in polypropylene ma-trix. The microfiltration membranes (polypropylene hollow fibers) were impregnated with solu-tions of some cellulosic derivatives: cellulose acetate, 2-hydroxyethyl-cellulose, methyl 2-hydroxyethyl-celluloseand sodium carboxymethyl-cellulose. The obtained membranes were characterized in terms of the separation performance of the amino acids considered (retention, flux, and selectivity) and from a morphological and structural point of view: scanning electron microscopy (SEM), high resolution SEM (HR-SEM), Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and thermal gravimetric analyzer (TGA). The re-sults obtained show that phenylalanine has the highest fluxes through all four types of mem-branes, followed by methionine and alanine. Of the four kinds of membrane, the most suitable for recuperative separation of the considered amino acids are those based on cellulose acetate and methyl 2-hydroxyethyl-cellulose. Full article

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24 pages, 5651 KiB

Open AccessArticle

An Analysis of the Effect of ZIF-8 Addition on the Separation Properties of Polysulfone at Various Temperatures

by Kseniya Papchenko, Giulio Risaliti, Matteo Ferroni, Meganne Christian and Maria Grazia De Angelis

Membranes 2021, 11(6), 427; https://doi.org/10.3390/membranes11060427 - 4 Jun 2021

Cited by 9 | Viewed by 4286

Abstract

The transport of H₂, He, CO₂, O₂, CH₄, and N₂ at three temperatures up to 65 °C was measured in dense, thick composite films formed by amorphous Polysulfone (PSf) and particles of the size-selective [...] Read more.

The transport of H₂, He, CO₂, O₂, CH₄, and N₂ at three temperatures up to 65 °C was measured in dense, thick composite films formed by amorphous Polysulfone (PSf) and particles of the size-selective zeolitic imidazolate framework 8 (ZIF-8) at loadings up to 16 wt%. The morphological and structural properties of the membranes were analyzed via SEM and density measurement. The addition of ZIF-8 to PSf enhances the H₂ and He permeabilities up to 480% with respect to the pure polymer, while the ideal H₂/CO₂ and He/CO₂ selectivities of MMMs reach values up to 30–40% higher than those of pure PSf. The relative permeability and diffusivity enhancements are higher than those obtained in other polymers, such as PPO, with the same amount of filler. The Maxwell–Wagner–Sillars model is able to represent the MMM H₂/CO₂ separation performance for filler volume fractions below 10%. Full article

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25 pages, 5652 KiB

Open AccessEditor’s ChoiceReview

Polymers and Solvents Used in Membrane Fabrication: A Review Focusing on Sustainable Membrane Development

by Xiaobo Dong, David Lu, Tequila A. L. Harris and Isabel C. Escobar

Membranes 2021, 11(5), 309; https://doi.org/10.3390/membranes11050309 - 23 Apr 2021

Cited by 134 | Viewed by 22416

Abstract

(1) Different methods have been applied to fabricate polymeric membranes with non-solvent induced phase separation (NIPS) being one of the mostly widely used. In NIPS, a solvent or solvent blend is required to dissolve a polymer or polymer blend. N-methyl-2-pyrrolidone (NMP), dimethylacetamide [...] Read more.

(1) Different methods have been applied to fabricate polymeric membranes with non-solvent induced phase separation (NIPS) being one of the mostly widely used. In NIPS, a solvent or solvent blend is required to dissolve a polymer or polymer blend. N-methyl-2-pyrrolidone (NMP), dimethylacetamide (DMAc), dimethylformamide (DMF) and other petroleum-derived solvents are commonly used to dissolve some petroleum-based polymers. However, these components may have negative impacts on the environment and human health. Therefore, using greener and less toxic components is of great interest for increasing membrane fabrication sustainability. The chemical structure of membranes is not affected by the use of different solvents, polymers, or by the differences in fabrication scale. On the other hand, membrane pore structures and surface roughness can change due to differences in diffusion rates associated with different solvents/co-solvents diffusing into the non-solvent and with differences in evaporation time. (2) Therefore, in this review, solvents and polymers involved in the manufacturing process of membranes are proposed to be replaced by greener/less toxic alternatives. The methods and feasibility of scaling up green polymeric membrane manufacturing are also examined. Full article

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19 pages, 6110 KiB

Open AccessArticle

Use of Ionic Liquids and Co-Solvents for Synthesis of Thin-Film Composite Membranes

by Peter-Renaat Van den Mooter, Liridona Dedvukaj and Ivo F. J. Vankelecom

Membranes 2021, 11(4), 297; https://doi.org/10.3390/membranes11040297 - 20 Apr 2021

Cited by 6 | Viewed by 3394

Abstract

Polyamide (PA) thin-film composite (TFC) membranes are commonly applied in reversed osmosis (RO) and nanofiltration (NF) applications due to their thin, dense top-layer, and high selectivity. Recently, the conventional organic phase (i.e., hexane) during interfacial polymerization (IP) was replaced by less toxic ionic [...] Read more.

Polyamide (PA) thin-film composite (TFC) membranes are commonly applied in reversed osmosis (RO) and nanofiltration (NF) applications due to their thin, dense top-layer, and high selectivity. Recently, the conventional organic phase (i.e., hexane) during interfacial polymerization (IP) was replaced by less toxic ionic liquids (ILs) which led to excellent membrane performances. As the high price of most ILs limits their up-scaling, the potential use of inexpensive Aliquat was investigated in this study. The thin-film composite (TFC) membranes were optimized to remove flavor compounds, i.e., ethyl acetate (EA) and isoamyl acetate (IA), from a fermentation broth. A multi-parameter optimization was set-up involving type of support, reaction time for IP, water content of Aliquat, and concentration of both monomers m-phenylenediamine (MPD) and trimesoylchloride (TMC). The membranes prepared using Aliquat showed similar fluxes as those prepared from a reference IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([C₄mpyr][Tf₂N]) but with better EA and IA retentions, even better than for a commercial RO membrane (GEA type AF). Finally, the recently introduced epoxide-curing of Bisphenol A diglycidyl ether (BADGE) with 1,6-hexanediamine (HDA) was investigated using Aliquat as organic phase. It is the first time this type of IP was performed in combination with an IL as organic phase. The resulting membrane was used in the filtration of a 35 µM Rose Bengal (RB) in 20 wt% dimethylformamide/ water (DMF/H₂O) feed mixture. A well-crosslinked poly(β-alkanolamine) film was obtained with a > 97% retention. Full article

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28 pages, 19291 KiB

Open AccessArticle

Removing of the Sulfur Compounds by Impregnated Polypropylene Fibers with Silver Nanoparticles-Cellulose Derivatives for Air Odor Correction

by Aurelia Cristina Nechifor, Simona Cotorcea, Constantin Bungău, Paul Constantin Albu, Dumitru Pașcu, Ovidiu Oprea, Alexandra Raluca Grosu, Andreia Pîrțac and Gheorghe Nechifor

Membranes 2021, 11(4), 256; https://doi.org/10.3390/membranes11040256 - 1 Apr 2021

Cited by 35 | Viewed by 3929

Abstract

The unpleasant odor that appears in the industrial and adjacent waste processing areas is a permanent concern for the protection of the environment and, especially, for the quality of life. Among the many variants for removing substance traces, which give an unpleasant smell [...] Read more.

The unpleasant odor that appears in the industrial and adjacent waste processing areas is a permanent concern for the protection of the environment and, especially, for the quality of life. Among the many variants for removing substance traces, which give an unpleasant smell to the air, membrane-based methods or techniques are viable options. Their advantages consist of installation simplicity and scaling possibility, selectivity; moreover, the flows of odorous substances are direct, automation is complete by accessible operating parameters (pH, temperature, ionic strength), and the operation costs are low. The paper presents the process of obtaining membranes from cellulosic derivatives containing silver nanoparticles, using accessible raw materials (namely motion picture films from abandoned archives). The technique used for membrane preparation was the immersion precipitation for phase inversion of cellulosic polymer solutions in methylene chloride: methanol, 2:1 volume. The membranes obtained were morphologically and structurally characterized by scanning electron microscopy (SEM) and high resolution SEM (HR SEM), energy dispersive X-ray analysis (EDAX), Fourier transform infrared spectrometry (FTIR), thermal analysis (TG, ATD). Then, the membrane performance process (extraction efficiency and species flux) was determined using hydrogen sulfide (H₂S) and ethanethiol (C₂H₅SH) as target substances. Full article

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17 pages, 4470 KiB

Open AccessArticle

“Artificial Wood” Lignocellulosic Membranes: Influence of Kraft Lignin on the Properties and Gas Transport in Tunicate-Based Nanocellulose Composites

by Ievgen Pylypchuk, Roman Selyanchyn, Tetyana Budnyak, Yadong Zhao, Mikael Lindström, Shigenori Fujikawa and Olena Sevastyanova

Membranes 2021, 11(3), 204; https://doi.org/10.3390/membranes11030204 - 13 Mar 2021

Cited by 8 | Viewed by 3810

Abstract

Nanocellulose membranes based on tunicate-derived cellulose nanofibers, starch, and ~5% wood-derived lignin were investigated using three different types of lignin. The addition of lignin into cellulose membranes increased the specific surface area (from 5 to ~50 m²/g), however the fine porous [...] Read more.

Nanocellulose membranes based on tunicate-derived cellulose nanofibers, starch, and ~5% wood-derived lignin were investigated using three different types of lignin. The addition of lignin into cellulose membranes increased the specific surface area (from 5 to ~50 m²/g), however the fine porous geometry of the nanocellulose with characteristic pores below 10 nm in diameter remained similar for all membranes. The permeation of H₂, CO₂, N₂, and O₂ through the membranes was investigated and a characteristic Knudsen diffusion through the membranes was observed at a rate proportional to the inverse of their molecular sizes. Permeability values, however, varied significantly between samples containing different lignins, ranging from several to thousands of barrers (10⁻¹⁰ cm³ (STP) cm cm⁻² s⁻¹ cmHg⁻¹cm), and were related to the observed morphology and lignin distribution inside the membranes. Additionally, the addition of ~5% lignin resulted in a significant increase in tensile strength from 3 GPa to ~6–7 GPa, but did not change thermal properties (glass transition or thermal stability). Overall, the combination of plant-derived lignin as a filler or binder in cellulose–starch composites with a sea-animal derived nanocellulose presents an interesting new approach for the fabrication of membranes from abundant bio-derived materials. Future studies should focus on the optimization of these types of membranes for the selective and fast transport of gases needed for a variety of industrial separation processes. Full article

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