Membranes

407 KiB

Open AccessArticle

Synthesis and Characterisation of ETS-10/Acetate-based Ionic Liquid/Chitosan Mixed Matrix Membranes for CO₂/N₂ Permeation

by Clara Casado-Coterillo, María Del Mar López-Guerrero and Ángel Irabien

Membranes 2014, 4(2), 287-301; https://doi.org/10.3390/membranes4020287 - 19 Jun 2014

Cited by 50 | Viewed by 7165

Abstract

Mixed matrix membranes (MMMs) were prepared by incorporating organic surfactant-free hydrothermally synthesised ETS-10 and 1-ethyl-3-methylimidazolium acetate ionic liquid (IL) to chitosan (CS) polymer matrix. The membrane material characteristics and permselectivity performance of the two-component membranes were compared with the three-component membrane and the [...] Read more.

Mixed matrix membranes (MMMs) were prepared by incorporating organic surfactant-free hydrothermally synthesised ETS-10 and 1-ethyl-3-methylimidazolium acetate ionic liquid (IL) to chitosan (CS) polymer matrix. The membrane material characteristics and permselectivity performance of the two-component membranes were compared with the three-component membrane and the pure CS membrane. The addition of IL increased CO₂ solubility of the polymer, and, thus, the CO₂ affinity was maintained for the MMMs, which can be correlated with the crystallinity, measured by FT-IR, and void fraction calculations from differences between theoretical and experimental densities. The mechanical resistance was enhanced by the ETS-10 nanoparticles, and flexibility decreased in the two-component ETS-10/CS MMMs, but the flexibility imparted by the IL remained in three-component ETS-10/IL/CS MMMs. The results of this work provide insight into another way of facing the adhesion challenge in MMMs and obtain CO₂ selective MMMs from renewable or green chemistry materials. Full article

(This article belongs to the Special Issue Nanocomposite Membranes)

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277 KiB

Open AccessArticle

Experimental Investigation into the Transmembrane Electrical Potential of the Forward Osmosis Membrane Process in Electrolyte Solutions

by Lixia Bian, Yanyan Fang and Xiaolin Wang

Membranes 2014, 4(2), 275-286; https://doi.org/10.3390/membranes4020275 - 19 Jun 2014

Cited by 6 | Viewed by 6007

Abstract

The transmembrane electrical potential (TMEP) in a forward osmosis membrane process with a single electrolyte solution as the draw and feed solutions was investigated by experiments. The effects of membrane orientation, the electrolyte species (KCl, NaCl, MgCl₂, and CaCl₂), [...] Read more.

The transmembrane electrical potential (TMEP) in a forward osmosis membrane process with a single electrolyte solution as the draw and feed solutions was investigated by experiments. The effects of membrane orientation, the electrolyte species (KCl, NaCl, MgCl₂, and CaCl₂), concentration and concentration ratio of solutions at both sides of membrane on water flux and TMEP were investigated. The results showed that the TMEPs at different membrane orientation cannot completely coincide, which confirmed the effect of membrane asymmetry. The ion diffusion coefficients significantly affected the TMEP across the membrane, with different patterns for different electrolytes and concentrations. Full article

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

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392 KiB

Open AccessArticle

Membrane Potential Generated by Ion Adsorption

by Hirohisa Tamagawa and Sachi Morita

Membranes 2014, 4(2), 257-274; https://doi.org/10.3390/membranes4020257 - 12 Jun 2014

Cited by 9 | Viewed by 7902

Abstract

It has been widely acknowledged that the Goldman-Hodgkin-Katz (GHK) equation fully explains membrane potential behavior. The fundamental facet of the GHK equation lies in its consideration of permeability of membrane to ions, when the membrane serves as a separator for separating two electrolytic [...] Read more.

It has been widely acknowledged that the Goldman-Hodgkin-Katz (GHK) equation fully explains membrane potential behavior. The fundamental facet of the GHK equation lies in its consideration of permeability of membrane to ions, when the membrane serves as a separator for separating two electrolytic solutions. The GHK equation describes that: variation of membrane permeability to ion in accordance with ion species results in the variation of the membrane potential. However, nonzero potential was observed even across the impermeable membrane (or separator) separating two electrolytic solutions. It gave rise to a question concerning the validity of the GHK equation for explaining the membrane potential generation. In this work, an alternative theory was proposed. It is the adsorption theory. The adsorption theory attributes the membrane potential generation to the ion adsorption onto the membrane (or separator) surface not to the ion passage through the membrane (or separator). The computationally obtained potential behavior based on the adsorption theory was in good agreement with the experimentally observed potential whether the membrane (or separator) was permeable to ions or not. It was strongly speculated that the membrane potential origin could lie primarily in the ion adsorption on the membrane (or separator) rather than the membrane permeability to ions. It might be necessary to reconsider the origin of membrane potential which has been so far believed explicable by the GHK equation. Full article

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1863 KiB

Open AccessArticle

The Effect of Chain Structures on the Crystallization Behavior and Membrane Formation of Poly(Vinylidene Fluoride) Copolymers

by Wenzhong Ma, Haoge Yuan and Xiaolin Wang

Membranes 2014, 4(2), 243-256; https://doi.org/10.3390/membranes4020243 - 19 May 2014

Cited by 37 | Viewed by 9352

Abstract

The crystallization behaviors of two copolymers of PVDF were studied, and the effect of copolymerized chains on the crystallization behavior was investigated. The results indicated that both copolymers had a lowered crystallization temperature and crystallinity. The crystallization rate was improved by the copolymer [...] Read more.

The crystallization behaviors of two copolymers of PVDF were studied, and the effect of copolymerized chains on the crystallization behavior was investigated. The results indicated that both copolymers had a lowered crystallization temperature and crystallinity. The crystallization rate was improved by the copolymer with symmetrical units in PVDF chains, but hindered by asymmetrical units, compared with the neat PVDF. The symmetrical units in PVDF chains favored the β-crystals with fiber-like structures. According to the solubility parameter rule, methyl salicylate (MS) can be chosen as a diluent for PVDF copolymers. Both diluted systems had liquid-liquid (L-L) regions in the phase diagrams, which was due to the lowered crystallization temperature. Full article

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

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282 KiB

Open AccessArticle

Filtration Characterization Method as Tool to Assess Membrane Bioreactor Sludge Filterability—The Delft Experience

by Maria Lousada-Ferreira, Pawel Krzeminski, Stefan Geilvoet, Adrien Moreau, Jose A. Gil, Herman Evenblij, Jules B. Van Lier and Jaap H. J. M. Van der Graaf

Membranes 2014, 4(2), 227-242; https://doi.org/10.3390/membranes4020227 - 30 Apr 2014

Cited by 8 | Viewed by 7099

Abstract

Prevention and removal of fouling is often the most energy intensive process in Membrane Bioreactors (MBRs), responsible for 40% to 50% of the total specific energy consumed in submerged MBRs. In the past decade, methods were developed to quantify and qualify fouling, aiming [...] Read more.

Prevention and removal of fouling is often the most energy intensive process in Membrane Bioreactors (MBRs), responsible for 40% to 50% of the total specific energy consumed in submerged MBRs. In the past decade, methods were developed to quantify and qualify fouling, aiming to support optimization in MBR operation. Therefore, there is a need for an evaluation of the lessons learned and how to proceed. In this article, five different methods for measuring MBR activated sludge filterability and critical flux are described, commented and evaluated. Both parameters characterize the fouling potential in full-scale MBRs. The article focuses on the Delft Filtration Characterization method (DFCm) as a convenient tool to characterize sludge properties, namely on data processing, accuracy, reproducibility, reliability, and applicability, defining the boundaries of the DFCm. Significant progress was made concerning fouling measurements in particular by using straight forward approaches focusing on the applicability of the obtained results. Nevertheless, a fouling measurement method is still to be defined which is capable of being unequivocal, concerning the fouling parameters definitions; practical and simple, in terms of set-up and operation; broad and useful, in terms of obtained results. A step forward would be the standardization of the aforementioned method to assess the sludge filtration quality. Full article

(This article belongs to the Special Issue Membrane Hybrid Processes)

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591 KiB

Open AccessArticle

Polymeric Pseudo-Liquid Membranes from Poly(N-oleylacrylamide)

by Hiroko Shiono and Masakazu Yoshikawa

Membranes 2014, 4(2), 210-226; https://doi.org/10.3390/membranes4020210 - 30 Apr 2014

Cited by 3 | Viewed by 6321

Abstract

A polymeric pseudo-liquid membrane (PPLM) was constructed from poly(N-oleylacrylamide) (PC18AAm), which exhibited a rubbery state under membrane transport conditions and used as the membrane matrix. In the present study, dibenzo-18-crown-6 (DB18C6) and dibenzo-21-crown-7 (DB21C7) were adopted as transporters for alkali metal [...] Read more.

A polymeric pseudo-liquid membrane (PPLM) was constructed from poly(N-oleylacrylamide) (PC18AAm), which exhibited a rubbery state under membrane transport conditions and used as the membrane matrix. In the present study, dibenzo-18-crown-6 (DB18C6) and dibenzo-21-crown-7 (DB21C7) were adopted as transporters for alkali metal ions. KCl was adopted as a model substrate for DB18C6 and CsCl the latter. Chiral transporter, O-allyl-N-(9-anthracenylmethyl)cinchonidinium bromide (AAMC) was used as a transporter for chiral separation of a racemic mixture of phenylglycine (Phegly). The l-somer was transported in preference to the antipode. The present study revealed that PPLMs are applicable to membrane transport, such as metal ion transport and chiral separation. Full article

(This article belongs to the Special Issue Advances in Liquid Membranes)

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516 KiB

Open AccessArticle

Effect of Cross-Linking on the Mechanical and Thermal Properties of Poly(amidoamine) Dendrimer/Poly(vinyl alcohol) Hybrid Membranes for CO₂ Separation

by Shuhong Duan, Teruhiko Kai, Takashi Saito, Kota Yamazaki and Kenichi Ikeda

Membranes 2014, 4(2), 200-209; https://doi.org/10.3390/membranes4020200 - 08 Apr 2014

Cited by 20 | Viewed by 7587

Abstract

Poly(amidoamine) (PAMAM) dendrimers were incorporated into cross-linked poly(vinyl alcohol) (PVA) matrix to improve carbon dioxide (CO₂) separation performance at elevated pressures. In our previous studies, PAMAM/PVA hybrid membranes showed high CO₂ separation properties from CO₂/H₂ mixed gases. [...] Read more.

Poly(amidoamine) (PAMAM) dendrimers were incorporated into cross-linked poly(vinyl alcohol) (PVA) matrix to improve carbon dioxide (CO₂) separation performance at elevated pressures. In our previous studies, PAMAM/PVA hybrid membranes showed high CO₂ separation properties from CO₂/H₂ mixed gases. In this study, three types of organic Ti metal compounds were selected as PVA cross-linkers that were used to prepare PAMAM/cross-linked PVA hybrid membranes. Characterization of the PAMAM/cross-linked PVA hybrid membranes was conducted using nanoindentation and thermogravimetric analyses. The effects of the cross-linker and CO₂ partial pressure in the feed gas on CO₂ separation performance were discussed. H₂O and CO₂ sorption of the PAMAM/PVA hybrid membranes were investigated to explain the obtained CO₂ separation efficiencies. Full article

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

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3481 KiB

Open AccessArticle

Preparation of Sulfobetaine-Grafted PVDF Hollow Fiber Membranes with a Stably Anti-Protein-Fouling Performance

by Qian Li, Han-Han Lin and Xiao-Lin Wang

Membranes 2014, 4(2), 181-199; https://doi.org/10.3390/membranes4020181 - 08 Apr 2014

Cited by 15 | Viewed by 6794

Abstract

Based on a two-step polymerization method, two sulfobetaine-based zwitterionic monomers, including 3-(methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide (MPDSAH) and 2-(methacryloyloxyethyl) ethyl-dimethyl-(3-sulfopropyl) ammonium (MEDSA), were successfully grafted from poly(vinylidene fluoride) (PVDF) hollow fiber membrane surfaces in the presence of N,N′-methylene bisacrylamide (MBAA) as [...] Read more.

Based on a two-step polymerization method, two sulfobetaine-based zwitterionic monomers, including 3-(methacryloylamino) propyl-dimethyl-(3-sulfopropyl) ammonium hydroxide (MPDSAH) and 2-(methacryloyloxyethyl) ethyl-dimethyl-(3-sulfopropyl) ammonium (MEDSA), were successfully grafted from poly(vinylidene fluoride) (PVDF) hollow fiber membrane surfaces in the presence of N,N′-methylene bisacrylamide (MBAA) as a cross-linking agent. The mechanical properties of the PVDF membrane were improved by the zwitterionic surface layers. The surface hydrophilicity of PVDF membranes was significantly enhanced and the polyMPDSAH-g-PVDF membrane showed a higher hydrophilicity due to the higher grafting amount. Compared to the polyMEDSA-g-PVDF membrane, the polyMPDSAH-g-PVDF membrane showed excellent significantly better anti-protein-fouling performance with a flux recovery ratio (RFR) higher than 90% during the cyclic filtration of a bovine serum albumin (BSA) solution. The polyMPDSAH-g-PVDF membrane showed an obvious electrolyte-responsive behavior and its protein-fouling-resistance performance was improved further during the filtration of the protein solution with 100 mmol/L of NaCl. After cleaned with a membrane cleaning solution for 16 days, the grafted MPDSAH layer on the PVDF membrane could be maintain without any chang; however, the polyMEDSA-g-PVDF membrane lost the grafted MEDSA layer after this treatment. Therefore, the amide group of sulfobetaine, which contributed significantly to the higher hydrophilicity and stability, was shown to be imperative in modifying the PVDF membrane for a stable anti-protein-fouling performance via the two-step polymerization method. Full article

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

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351 KiB

Open AccessArticle

Nanofiltration of Mine Water: Impact of Feed pH and Membrane Charge on Resource Recovery and Water Discharge

by Mark Mullett, Roberta Fornarelli and David Ralph

Membranes 2014, 4(2), 163-180; https://doi.org/10.3390/membranes4020163 - 27 Mar 2014

Cited by 80 | Viewed by 9850

Abstract

Two nanofiltration membranes, a Dow NF 270 polyamide thin film and a TriSep TS 80 polyamide thin film, were investigated for their retention of ionic species when filtering mine influenced water streams at a range of acidic pH values. The functional iso-electric point [...] Read more.

Two nanofiltration membranes, a Dow NF 270 polyamide thin film and a TriSep TS 80 polyamide thin film, were investigated for their retention of ionic species when filtering mine influenced water streams at a range of acidic pH values. The functional iso-electric point of the membranes, characterized by changes in retention over a small pH range, were examined by filtering solutions of sodium sulphate. Both membranes showed changes in retention at pH 3, suggesting a zero net charge on the membranes at this pH. Copper mine drainage and synthetic solutions of mine influenced water were filtered using the same membranes. These solutions were characterized by pH values within 2 and 5, thus crossing the iso-electric point of both membranes. Retention of cations was maximized when the feed solution pH was less than the iso-electric point of the membrane. In these conditions, the membrane has a net positive charge, reducing the transmission rate of cations. From the recoveries of a range of cations, the suitability of nanofiltration was discussed relative to the compliance with mine water discharge criteria and the recovery of valuable commodity metals. The nanofiltration process was demonstrated to offer advantages in metal recovery from mine waste streams, concomitantly enabling discharge criteria for the filtrate disposal to be met. Full article

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Membranes, Volume 4, Issue 2 (June 2014) – 9 articles , Pages 163-301

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