Membranes

1115 KiB

Open AccessArticle

Performance and Long-Term Stability of Pd/PSS and Pd/Al₂O₃ Membranes for Hydrogen Separation

by Simona Liguori, Adolfo Iulianelli, Francesco Dalena, Pietro Pinacci, Francesca Drago, Maria Broglia, Yan Huang and Angelo Basile

Membranes 2014, 4(1), 143-162; https://doi.org/10.3390/membranes4010143 - 6 Mar 2014

Cited by 51 | Viewed by 8810

Abstract

The present work is focused on the investigation of the performance and long-term stability of two composite palladium membranes under different operating conditions. One membrane (Pd/porous stainless steel (PSS)) is characterized by a ~10 µm-thick palladium layer on a porous stainless steel substrate, [...] Read more.

The present work is focused on the investigation of the performance and long-term stability of two composite palladium membranes under different operating conditions. One membrane (Pd/porous stainless steel (PSS)) is characterized by a ~10 µm-thick palladium layer on a porous stainless steel substrate, which is pretreated by means of surface modification and oxidation; the other membrane (Pd/Al₂O₃) is constituted by a ~7 µm-thick palladium layer on an asymmetric microporous Al₂O₃ substrate. The operating temperature and pressure ranges, used for studying the performance of these two kinds of membranes, are 350–450 °C and 200–800 kPa, respectively. The H₂ permeances and the H₂/N₂ selectivities of both membranes were investigated and compared with literature data. At 400 °C and 200 kPa as pressure difference, Pd/PSS and Pd/Al₂O₃ membranes exhibited an H₂/N₂ ideal selectivity equal to 11700 and 6200, respectively, showing stability for 600 h. Thereafter, H₂/N₂ selectivity of both membranes progressively decreased and after around 2000 h, dropped dramatically to 55 and 310 for the Pd/PSS and Pd/Al₂O₃ membranes, respectively. As evidenced by Scanning Electron Microscope (SEM) analyses, the pinholes appear on the whole surface of the Pd/PSS membrane and this is probably due to release of sulphur from the graphite seal rings. Full article

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1726 KiB

Open AccessArticle

Preparation and Characterization of Nanocomposite Polymer Membranes Containing Functionalized SnO₂ Additives

by Roberto Scipioni, Delia Gazzoli, Francesca Teocoli, Oriele Palumbo, Annalisa Paolone, Neluta Ibris, Sergio Brutti and Maria Assunta Navarra

Membranes 2014, 4(1), 123-142; https://doi.org/10.3390/membranes4010123 - 5 Mar 2014

Cited by 73 | Viewed by 10019

Abstract

In the research of new nanocomposite proton-conducting membranes, SnO₂ ceramic powders with surface functionalization have been synthesized and adopted as additives in Nafion-based polymer systems. Different synthetic routes have been explored to obtain suitable, nanometer-sized sulphated tin oxide particles. Structural and morphological [...] Read more.

In the research of new nanocomposite proton-conducting membranes, SnO₂ ceramic powders with surface functionalization have been synthesized and adopted as additives in Nafion-based polymer systems. Different synthetic routes have been explored to obtain suitable, nanometer-sized sulphated tin oxide particles. Structural and morphological characteristics, as well as surface and bulk properties of the obtained oxide powders, have been determined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier Transform Infrared (FTIR) and Raman spectroscopies, N₂ adsorption, and thermal gravimetric analysis (TGA). In addition, dynamic mechanical analysis (DMA), atomic force microscopy (AFM), thermal investigations, water uptake (WU) measurements, and ionic exchange capacity (IEC) tests have been used as characterization tools for the nanocomposite membranes. The nature of the tin oxide precursor, as well as the synthesis procedure, were found to play an important role in determining the morphology and the particle size distribution of the ceramic powder, this affecting the effective functionalization of the oxides. The incorporation of such particles, having sulphate groups on their surface, altered some peculiar properties of the resulting composite membrane, such as water content, thermo-mechanical, and morphological characteristics. Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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817 KiB

Open AccessArticle

Solidification Behavior of Polymer Solution during Membrane Preparation by Thermally Induced Phase Separation

by Toru Ishigami, Yoko Nii, Yoshikage Ohmukai, Saeid Rajabzadeh and Hideto Matsuyama

Membranes 2014, 4(1), 113-122; https://doi.org/10.3390/membranes4010113 - 28 Feb 2014

Cited by 29 | Viewed by 8349

Abstract

The solidification behavior of poly(vinylidene fluoride) (PVDF) solution during membrane preparation by thermally induced phase separation (TIPS) was investigated. Apparatus newly developed in our laboratory was used to quantitatively measure membrane stiffness during phase separation. In this apparatus, a cooling polymer solution, placed [...] Read more.

The solidification behavior of poly(vinylidene fluoride) (PVDF) solution during membrane preparation by thermally induced phase separation (TIPS) was investigated. Apparatus newly developed in our laboratory was used to quantitatively measure membrane stiffness during phase separation. In this apparatus, a cooling polymer solution, placed on a stage, is moved upwards and the surface of the polymer solution contacts a sphere attached to the tip of a needle. The displacement of a blade spring attached to the needle is then measured by a laser displacement sensor. Different phase separation modes, such as liquid-liquid (L-L) phase separation and solid-liquid (S-L) phase separation (polymer crystallization) were investigated. In the case of S-L phase separation, the stiffness of the solution surface began to increase significantly just before termination of crystallization. In contrast, L-L phase separation delayed solidification of the solution. This was because mutual contact of the spherulites was obstructed by droplets of polymer-lean phase formed during L-L phase separation. Thus, the solidification rate was slower for the L-L phase separation system than for the S-L phase separation system. Full article

(This article belongs to the Special Issue Selected Papers from AMS8 Conference (July 2013, Xi’an, China))

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490 KiB

Open AccessArticle

Improvement of Membrane Performances to Enhance the Yield of Vanillin in a Pervaporation Reactor

by Giovanni Camera-Roda, Antonio Cardillo, Vittorio Loddo, Leonardo Palmisano and Francesco Parrino

Membranes 2014, 4(1), 96-112; https://doi.org/10.3390/membranes4010096 - 28 Feb 2014

Cited by 23 | Viewed by 8221

Abstract

In membrane reactors, the interaction of reaction and membrane separation can be exploited to achieve a “process intensification”, a key objective of sustainable development. In the present work, the properties that the membrane must have to obtain this result in a pervaporation reactor [...] Read more.

In membrane reactors, the interaction of reaction and membrane separation can be exploited to achieve a “process intensification”, a key objective of sustainable development. In the present work, the properties that the membrane must have to obtain this result in a pervaporation reactor are analyzed and discussed. Then, the methods to enhance these properties are investigated for the photocatalytic synthesis of vanillin, which represents a case where the recovery from the reactor of vanillin by means of pervaporation while it is produced allows a substantial improvement of the yield, since its further oxidation is thus prevented. To this end, the phenomena that control the permeation of both vanillin and the reactant (ferulic acid) are analyzed, since they ultimately affect the performances of the membrane reactor. The results show that diffusion of the aromatic compounds takes place in the presence of low concentration gradients, so that the process is controlled by other phenomena, in particular by the equilibrium with the vapor at the membrane-permeate interface. On this basis, it is demonstrated that the performances are enhanced by increasing the membrane thickness and/or the temperature, whereas the pH begins to limit the process only at values higher than 6.5. Full article

(This article belongs to the Special Issue Membranes in Process Intensification)

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909 KiB

Open AccessArticle

Preparation of Polyvinylidene Fluoride (PVDF) Hollow Fiber Hemodialysis Membranes

by Qinglei Zhang, Xiaolong Lu and Lihua Zhao

Membranes 2014, 4(1), 81-95; https://doi.org/10.3390/membranes4010081 - 27 Feb 2014

Cited by 58 | Viewed by 12523

Abstract

In this study, the polyvinylidene fluoride (PVDF) hollow fiber hemodialysis membranes were prepared by non-solvent induced phase separation (NIPS). The influences of PVDF membrane thickness and polyethylene glycol (PEG) content on membrane morphologies, pore size, mechanical and permeable performance were investigated. It was [...] Read more.

In this study, the polyvinylidene fluoride (PVDF) hollow fiber hemodialysis membranes were prepared by non-solvent induced phase separation (NIPS). The influences of PVDF membrane thickness and polyethylene glycol (PEG) content on membrane morphologies, pore size, mechanical and permeable performance were investigated. It was found that membrane thickness and PEG content affected both the structure and performance of hollow fiber membranes. The tensile strength and rejection of bovine serum albumin (BSA) increased with increasing membrane thickness, while the Ultrafiltration flux (UF) flux of pure water was the opposite. The tensile strength, porosity and rejection of BSA increased with increasing PEG content within a certain range. Compared with commercial F60S membrane, the PVDF hollow fiber membrane showed higher mechanical and permeable performance. It was proven that PVDF material had better hydrophilicity and lower BSA adsorption, which was more suitable for hemodialysis. All the results indicate that PVDF hollow fiber membrane is promising as a hemodialysis membrane. Full article

(This article belongs to the Special Issue Selected Papers from AMS8 Conference (July 2013, Xi’an, China))

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114 KiB

Open AccessEditorial

Acknowledgement to Reviewers of Membranes in 2013

by Membranes Editorial Office

Membranes 2014, 4(1), 79-80; https://doi.org/10.3390/membranes4010079 - 24 Feb 2014

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Abstract

The editors of Membranes would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2013. [...] Full article

1257 KiB

Open AccessReview

Nanocomposites for Improved Physical Durability of Porous PVDF Membranes

by Chi Yan Lai, Andrew Groth, Stephen Gray and Mikel Duke

Membranes 2014, 4(1), 55-78; https://doi.org/10.3390/membranes4010055 - 24 Feb 2014

Cited by 41 | Viewed by 11960

Abstract

Current commercial polymer membranes have shown high performance and durability in water treatment, converting poor quality waters to higher quality suitable for drinking, agriculture and recycling. However, to extend the treatment into more challenging water sources containing abrasive particles, micro and ultrafiltration membranes [...] Read more.

Current commercial polymer membranes have shown high performance and durability in water treatment, converting poor quality waters to higher quality suitable for drinking, agriculture and recycling. However, to extend the treatment into more challenging water sources containing abrasive particles, micro and ultrafiltration membranes with enhanced physical durability are highly desirable. This review summarises the current limits of the existing polymeric membranes to treat harsh water sources, followed by the development of nanocomposite poly(vinylidene fluoride) (PVDF) membranes for improved physical durability. Various types of nanofillers including nanoparticles, carbon nanotubes (CNT) and nanoclays were evaluated for their effect on flux, fouling resistance, mechanical strength and abrasion resistance on PVDF membranes. The mechanisms of abrasive wear and how the more durable materials provide resistance was also explored. Full article

(This article belongs to the Special Issue Nanocomposite Membranes)

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728 KiB

Open AccessArticle

A Pervaporation Study of Ammonia Solutions Using Molecular Sieve Silica Membranes

by Xing Yang, Thomas Fraser, Darli Myat, Simon Smart, Jianhua Zhang, João C. Diniz da Costa, Audra Liubinas and Mikel Duke

Membranes 2014, 4(1), 40-54; https://doi.org/10.3390/membranes4010040 - 17 Feb 2014

Cited by 44 | Viewed by 9706

Abstract

An innovative concept is proposed to recover ammonia from industrial wastewater using a molecular sieve silica membrane in pervaporation (PV), benchmarked against vacuum membrane distillation (VMD). Cobalt and iron doped molecular sieve silica-based ceramic membranes were evaluated based on the ammonia concentration factor [...] Read more.

An innovative concept is proposed to recover ammonia from industrial wastewater using a molecular sieve silica membrane in pervaporation (PV), benchmarked against vacuum membrane distillation (VMD). Cobalt and iron doped molecular sieve silica-based ceramic membranes were evaluated based on the ammonia concentration factor downstream and long-term performance. A modified low-temperature membrane evaluation system was utilized, featuring the ability to capture and measure ammonia in the permeate. It was found that the silica membrane with confirmed molecular sieving features had higher water selectivity over ammonia. This was due to a size selectivity mechanism that favoured water, but blocked ammonia. However, a cobalt doped silica membrane previously treated with high temperature water solutions demonstrated extraordinary preference towards ammonia by achieving up to a 50,000 mg/L ammonia concentration (a reusable concentration level) measured in the permeate when fed with 800 mg/L of ammonia solution. This exceeded the concentration factor expected by the benchmark VMD process by four-fold, suspected to be due to the competitive adsorption of ammonia over water into the silica structure with pores now large enough to accommodate ammonia. However, this membrane showed a gradual decline in selectivity, suspected to be due to the degradation of the silica material/pore structure after several hours of operation. Full article

(This article belongs to the Special Issue Selected Papers from AMS8 Conference (July 2013, Xi’an, China))

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1152 KiB

Open AccessArticle

Carbon Nanotube- and Carbon Fiber-Reinforcement of Ethylene-Octene Copolymer Membranes for Gas and Vapor Separation

by Zuzana Sedláková, Gabriele Clarizia, Paola Bernardo, Johannes Carolus Jansen, Petr Slobodian, Petr Svoboda, Magda Kárászová, Karel Friess and Pavel Izak

Membranes 2014, 4(1), 20-39; https://doi.org/10.3390/membranes4010020 - 3 Jan 2014

Cited by 26 | Viewed by 9805

Abstract

Gas and vapor transport properties were studied in mixed matrix membranes containing elastomeric ethylene-octene copolymer (EOC or poly(ethylene-co-octene)) with three types of carbon fillers: virgin or oxidized multi-walled carbon nanotubes (CNTs) and carbon fibers (CFs). Helium, hydrogen, nitrogen, oxygen, methane, and [...] Read more.

Gas and vapor transport properties were studied in mixed matrix membranes containing elastomeric ethylene-octene copolymer (EOC or poly(ethylene-co-octene)) with three types of carbon fillers: virgin or oxidized multi-walled carbon nanotubes (CNTs) and carbon fibers (CFs). Helium, hydrogen, nitrogen, oxygen, methane, and carbon dioxide were used for gas permeation rate measurements. Vapor transport properties were studied for the aliphatic hydrocarbon (hexane), aromatic compound (toluene), alcohol (ethanol), as well as water for the representative samples. The mechanical properties and homogeneity of samples was checked by stress-strain tests. The addition of virgin CNTs and CFs improve mechanical properties. Gas permeability of EOC lies between that of the more permeable PDMS and the less permeable semi-crystalline polyethylene and polypropylene. Organic vapors are more permeable than permanent gases in the composite membranes, with toluene and hexane permeabilities being about two orders of magnitude higher than permanent gas permeability. The results of the carbon-filled membranes offer perspectives for application in gas/vapor separation with improved mechanical resistance. Full article

(This article belongs to the Special Issue Nanocomposite Membranes)

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1192 KiB

Open AccessArticle

Friedel–Crafts Crosslinked Highly Sulfonated Polyether Ether Ketone (SPEEK) Membranes for a Vanadium/Air Redox Flow Battery

by Géraldine Merle, Filipoi Carmen Ioana, Dan Eugen Demco, Michel Saakes and Seyed Schwan Hosseiny

Membranes 2014, 4(1), 1-19; https://doi.org/10.3390/membranes4010001 - 30 Dec 2013

Cited by 15 | Viewed by 9742

Abstract

Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl_² [...] Read more.

Highly conductive and low vanadium permeable crosslinked sulfonated poly(ether ether ketone) (cSPEEK) membranes were prepared by electrophilic aromatic substitution for a Vanadium/Air Redox Flow Battery (Vanadium/Air-RFB) application. Membranes were synthesized from ethanol solution and crosslinked under different temperatures with 1,4-benzenedimethanol and ZnCl_² via the Friedel–Crafts crosslinking route. The crosslinking mechanism under different temperatures indicated two crosslinking pathways: (a) crosslinking on the sulfonic acid groups; and (b) crosslinking on the backbone. It was observed that membranes crosslinked at a temperature of 150 °C lead to low proton conductive membranes, whereas an increase in crosslinking temperature and time would lead to high proton conductive membranes. High temperature crosslinking also resulted in an increase in anisotropy and water diffusion. Furthermore, the membranes were investigated for a Vanadium/Air Redox Flow Battery application. Membranes crosslinked at 200 °C for 30 min with a molar ratio between 2:1 (mol repeat unit:mol benzenedimethanol) showed a proton conductivity of 27.9 mS/cm and a 100 times lower VO²⁺crossover compared to Nafion. Full article

(This article belongs to the Special Issue Advancements in Membranes for Electrochemical Energy Applications)

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Membranes, Volume 4, Issue 1 (March 2014) – 10 articles , Pages 1-162

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