Membranes

3773 KiB

Open AccessFeature PaperArticle

Nanofiber Ion-Exchange Membranes for the Rapid Uptake and Recovery of Heavy Metals from Water

by Nithinart Chitpong and Scott M. Husson

Membranes 2016, 6(4), 59; https://doi.org/10.3390/membranes6040059 - 20 Dec 2016

Cited by 26 | Viewed by 6278

An evaluation of the performance of polyelectrolyte-modified nanofiber membranes was undertaken to determine their efficacy in the rapid uptake and recovery of heavy metals from impaired waters. The membranes were prepared by grafting poly(acrylic acid) (PAA) and poly(itaconic acid) (PIA) to cellulose nanofiber [...] Read more.

An evaluation of the performance of polyelectrolyte-modified nanofiber membranes was undertaken to determine their efficacy in the rapid uptake and recovery of heavy metals from impaired waters. The membranes were prepared by grafting poly(acrylic acid) (PAA) and poly(itaconic acid) (PIA) to cellulose nanofiber mats. Performance measurements quantified the dynamic ion-exchange capacity for cadmium (Cd), productivity, and recovery of Cd(II) from the membranes by regeneration. The dynamic binding capacities of Cd(II) on both types of nanofiber membrane were independent of the linear flow velocity, with a residence time of as low as 2 s. Analysis of breakthrough curves indicated that the mass flow rate increased rapidly at constant applied pressure after membranes approached equilibrium load capacity for Cd(II), apparently due to a collapse of the polymer chains on the membrane surface, leading to an increased porosity. This mechanism is supported by hydrodynamic radius (R_h) measurements for PAA and PIA obtained from dynamic light scattering, which show that R_h values decrease upon Cd(II) binding. Volumetric productivity was high for the nanofiber membranes, and reached 0.55 mg Cd/g/min. The use of ethylenediaminetetraacetic acid as regeneration reagent was effective in fully recovering Cd(II) from the membranes. Ion-exchange capacities were constant over five cycles of binding-regeneration. Full article

(This article belongs to the Special Issue Nanofiber Membranes: Materials and Applications)

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3456 KiB

Open AccessFeature PaperReview

Structure and Nanomechanics of Model Membranes by Atomic Force Microscopy and Spectroscopy: Insights into the Role of Cholesterol and Sphingolipids

by Berta Gumí-Audenis, Luca Costa, Francesco Carlá, Fabio Comin, Fausto Sanz and Marina I. Giannotti

Membranes 2016, 6(4), 58; https://doi.org/10.3390/membranes6040058 - 19 Dec 2016

Cited by 37 | Viewed by 12401

Abstract

Biological membranes mediate several biological processes that are directly associated with their physical properties but sometimes difficult to evaluate. Supported lipid bilayers (SLBs) are model systems widely used to characterize the structure of biological membranes. Cholesterol (Chol) plays an essential role in the [...] Read more.

Biological membranes mediate several biological processes that are directly associated with their physical properties but sometimes difficult to evaluate. Supported lipid bilayers (SLBs) are model systems widely used to characterize the structure of biological membranes. Cholesterol (Chol) plays an essential role in the modulation of membrane physical properties. It directly influences the order and mechanical stability of the lipid bilayers, and it is known to laterally segregate in rafts in the outer leaflet of the membrane together with sphingolipids (SLs). Atomic force microscope (AFM) is a powerful tool as it is capable to sense and apply forces with high accuracy, with distance and force resolution at the nanoscale, and in a controlled environment. AFM-based force spectroscopy (AFM-FS) has become a crucial technique to study the nanomechanical stability of SLBs by controlling the liquid media and the temperature variations. In this contribution, we review recent AFM and AFM-FS studies on the effect of Chol on the morphology and mechanical properties of model SLBs, including complex bilayers containing SLs. We also introduce a promising combination of AFM and X-ray (XR) techniques that allows for in situ characterization of dynamic processes, providing structural, morphological, and nanomechanical information. Full article

(This article belongs to the Special Issue Feature Papers)

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2071 KiB

Open AccessFeature PaperReview

Incorporation of Graphene-Related Carbon Nanosheets in Membrane Fabrication for Water Treatment: A Review

by Jenny Lawler

Membranes 2016, 6(4), 57; https://doi.org/10.3390/membranes6040057 - 19 Dec 2016

Cited by 20 | Viewed by 9432

Abstract

The minimization of the trade-off between the flux and the selectivity of membranes is a key area that researchers are continually working to optimise, particularly in the area of fabrication of novel membranes. Flux versus selectivity issues apply in many industrial applications of [...] Read more.

The minimization of the trade-off between the flux and the selectivity of membranes is a key area that researchers are continually working to optimise, particularly in the area of fabrication of novel membranes. Flux versus selectivity issues apply in many industrial applications of membranes, for example the unwanted diffusion of methanol in fuel cells, retention of valuable proteins in downstream processing of biopharmaceuticals, rejection of organic matter and micro-organisms in water treatment, or salt permeation in desalination. The incorporation of nanosheets within membrane structures can potentially lead to enhancements in such properties as the antifouling ability, hydrophilicy and permeability of membranes, with concomitant improvements in the flux/selectivity balance. Graphene nanosheets and derivatives such as graphene oxide and reduced graphene oxide have been investigated for this purpose, for example inclusion of nanosheets within the active layer of Reverse Osmosis or Nanofiltration membranes or the blending of nanosheets as fillers within Ultrafiltration membranes. This review summarizes the incorporation of graphene derivatives into polymeric membranes for water treatment with a focus on a number of industrial applications, including desalination and pharmaceutical removal, where enhancement of productivity and reduction in fouling characteristics have been afforded by appropriate incorporation of graphene derived nanosheets during membrane fabrication. Full article

(This article belongs to the Special Issue Feature Papers)

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2077 KiB

Open AccessFeature PaperArticle

Vitamin E Circular Dichroism Studies: Insights into Conformational Changes Induced by the Solvent’s Polarity

by Drew Marquardt, Brad J. Van Oosten, Mikel Ghelfi, Jeffrey Atkinson and Thad A. Harroun

Membranes 2016, 6(4), 56; https://doi.org/10.3390/membranes6040056 - 14 Dec 2016

Cited by 5 | Viewed by 6271

Abstract

We used circular dichroism (CD) to study differences in CD spectra between α-, δ-, and methylated-α-tocopherol in solvents with different polarities. CD spectra of the different tocopherol structures differ from each other in intensity and peak locations, which can [...] Read more.

We used circular dichroism (CD) to study differences in CD spectra between α-, δ-, and methylated-α-tocopherol in solvents with different polarities. CD spectra of the different tocopherol structures differ from each other in intensity and peak locations, which can be attributed to chromanol substitution and the ability to form hydrogen bonds. In addition, each structure was examined in different polarity solvents using the Reichardt index—a measure of the solvent’s ionizing ability, and a direct measurement of solvent–solute interactions. Differences across solvents indicate that hydrogen bonding is a key contributor to CD spectra at 200 nm. These results are a first step in examining the hydrogen bonding abilities of vitamin E in a lipid bilayer. Full article

(This article belongs to the Special Issue Feature Papers)

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5370 KiB

Open AccessFeature PaperReview

Application of Semipermeable Membranes in Glucose Biosensing

by Tanmay Kulkarni and Gymama Slaughter

Membranes 2016, 6(4), 55; https://doi.org/10.3390/membranes6040055 - 14 Dec 2016

Cited by 61 | Viewed by 14136

Abstract

Glucose biosensors have received significant attention in recent years due to the escalating mortality rate of diabetes mellitus. Although there is currently no cure for diabetes mellitus, individuals living with diabetes can lead a normal life by maintaining tight control of their blood [...] Read more.

Glucose biosensors have received significant attention in recent years due to the escalating mortality rate of diabetes mellitus. Although there is currently no cure for diabetes mellitus, individuals living with diabetes can lead a normal life by maintaining tight control of their blood glucose levels using glucose biosensors (e.g., glucometers). Current research in the field is focused on the optimization and improvement in the performance of glucose biosensors by employing a variety of glucose selective enzymes, mediators and semipermeable membranes to improve the electron transfer between the active center of the enzyme and the electrode substrate. Herein, we summarize the different semipermeable membranes used in the fabrication of the glucose biosensor, that result in improved biosensor sensitivity, selectivity, dynamic range, response time and stability. Full article

(This article belongs to the Special Issue Feature Papers)

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3805 KiB

Open AccessFeature PaperArticle

Treated Seawater as a Magnesium Source for Phosphorous Recovery from Wastewater—A Feasibility and Cost Analysis

by Cejna Anna Quist-Jensen, Mads Koustrup Jørgensen and Morten Lykkegaard Christensen

Membranes 2016, 6(4), 54; https://doi.org/10.3390/membranes6040054 - 13 Dec 2016

Cited by 21 | Viewed by 7389

Abstract

Conventional resources of phosphorous are at high risk of depletion in the near future due to current practices of its exploitation, thus new and improved exploration methodologies need to be developed to ensure phosphorous security. Today, some treatment plants recover phosphorous from municipal [...] Read more.

Conventional resources of phosphorous are at high risk of depletion in the near future due to current practices of its exploitation, thus new and improved exploration methodologies need to be developed to ensure phosphorous security. Today, some treatment plants recover phosphorous from municipal wastewater as struvite (MgNH₄PO₄·6H₂O). Magnesium is often added to the wastewater as MgCl₂·6H₂O to facilitate the phosphorous recovery. However, the use of magnesium increases the costs of the process and is not aligned with sustainable development, therefore, alternative magnesium sources have to be found. The current study analyzes the feasibility of integrated membrane processes for magnesium recovery from seawater for utilization in the phosphorous recovery process. The integrated membrane systems consist of nanofiltration (NF), membrane distillation (MD), and membrane crystallization (MCr). The lowest associated cost is found for standalone NF treatment. However, the additional treatment with MD and MCr produces fresh water and salts like NaCl or potentially other valuable minerals at the expense of low-grade heat. Full article

(This article belongs to the Special Issue Membrane Nanofiltration and Reverse Osmosis)

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6334 KiB

Open AccessFeature PaperReview

What Ion Flow along Ion Channels Can Tell us about Their Functional Activity

by Lucia Becucci and Rolando Guidelli

Membranes 2016, 6(4), 53; https://doi.org/10.3390/membranes6040053 - 13 Dec 2016

Cited by 14 | Viewed by 5192

Abstract

The functional activity of channel-forming peptides and proteins is most directly verified by monitoring the flow of physiologically relevant inorganic ions, such as Na⁺, K⁺ and Cl⁻, along the ion channels. Electrical current measurements across bilayer lipid membranes [...] Read more.

The functional activity of channel-forming peptides and proteins is most directly verified by monitoring the flow of physiologically relevant inorganic ions, such as Na⁺, K⁺ and Cl⁻, along the ion channels. Electrical current measurements across bilayer lipid membranes (BLMs) interposed between two aqueous solutions have been widely employed to this end and are still extensively used. However, a major drawback of BLMs is their fragility, high sensitivity toward vibrations and mechanical shocks, and low resistance to electric fields. To overcome this problem, metal-supported tethered BLMs (tBLMs) have been devised, where the BLM is anchored to the metal via a hydrophilic spacer that replaces and mimics the water phase on the metal side. However, only mercury-supported tBLMs can measure and regulate the flow of the above inorganic ions, thanks to mercury liquid state and high hydrogen overpotential. This review summarizes the main results achieved by BLMs incorporating voltage-gated channel-forming peptides, interpreting them on the basis of a kinetic mechanism of nucleation and growth. Hg-supported tBLMs are then described, and their potential for the investigation of voltage-gated and ohmic channels is illustrated by the use of different electrochemical techniques. Full article

(This article belongs to the Special Issue Feature Papers)

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Graphical abstract

2890 KiB

Open AccessReview

Process-Oriented Review of Bacterial Quorum Quenching for Membrane Biofouling Mitigation in Membrane Bioreactors (MBRs)

by Naila Bouayed, Nicolas Dietrich, Christine Lafforgue, Chung-Hak Lee and Christelle Guigui

Membranes 2016, 6(4), 52; https://doi.org/10.3390/membranes6040052 - 13 Dec 2016

Cited by 25 | Viewed by 7716

Abstract

Quorum Quenching (QQ) has been developed over the last few years to overcome practical issues related to membrane biofouling, which is currently the major difficulty thwarting the extensive development of membrane bioreactors (MBRs). QQ is the disruption of Quorum Sensing (QS), cell-to-cell communication [...] Read more.

Quorum Quenching (QQ) has been developed over the last few years to overcome practical issues related to membrane biofouling, which is currently the major difficulty thwarting the extensive development of membrane bioreactors (MBRs). QQ is the disruption of Quorum Sensing (QS), cell-to-cell communication enabling the bacteria to harmonize their behavior. The production of biofilm, which is recognized as a major part of the biocake formed on a membrane surface, and which leads to biofouling, has been found to be one of the bacterial behaviors controlled by QS. Since the enzymatic disruption of QS was reported to be efficient as a membrane biofouling mitigation technique in MBRs, the application of QQ to lab-scale MBRs has been the subject of much research using different approaches under different operating conditions. This paper gives an overview of the effectiveness of QQ in mitigating membrane biofouling in MBRs. It is based on the results of previous studies, using two microbial strains, Rhodococcus sp. BH4 and Pseudomonas sp. 1A1. The effect of bacterial QQ on the physical phenomena of the MBR process is analyzed, adopting an original multi-scale approach. Finally, the potential influence of the MBR operating conditions on QQ effectiveness is discussed. Full article

(This article belongs to the Special Issue Feature Papers)

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2868 KiB

Open AccessArticle

Investigating Sterol and Redox Regulation of the Ion Channel Activity of CLIC1 Using Tethered Bilayer Membranes

by Heba Al Khamici, Khondker R. Hossain, Bruce A. Cornell and Stella M. Valenzuela

Membranes 2016, 6(4), 51; https://doi.org/10.3390/membranes6040051 - 8 Dec 2016

Cited by 16 | Viewed by 5272

Abstract

The Chloride Intracellular Ion Channel (CLIC) family consists of six conserved proteins in humans. These are a group of enigmatic proteins, which adopt both a soluble and membrane bound form. CLIC1 was found to be a metamorphic protein, where under specific environmental triggers [...] Read more.

The Chloride Intracellular Ion Channel (CLIC) family consists of six conserved proteins in humans. These are a group of enigmatic proteins, which adopt both a soluble and membrane bound form. CLIC1 was found to be a metamorphic protein, where under specific environmental triggers it adopts more than one stable reversible soluble structural conformation. CLIC1 was found to spontaneously insert into cell membranes and form chloride ion channels. However, factors that control the structural transition of CLIC1 from being an aqueous soluble protein into a membrane bound protein have yet to be adequately described. Using tethered bilayer lipid membranes and electrical impedance spectroscopy system, herein we demonstrate that CLIC1 ion channel activity is dependent on the type and concentration of sterols in bilayer membranes. These findings suggest that membrane sterols play an essential role in CLIC1’s acrobatic switching from a globular soluble form to an integral membrane form, promoting greater ion channel conductance in membranes. What remains unclear is the precise nature of this regulation involving membrane sterols and ultimately determining CLIC1’s membrane structure and function as an ion channel. Furthermore, our impedance spectroscopy results obtained using CLIC1 mutants, suggest that the residue Cys24 is not essential for CLIC1’s ion channel function. However Cys24 does appear important for optimal ion channel activity. We also observe differences in conductance between CLIC1 reduced and oxidized forms when added to our tethered membranes. Therefore, we conclude that both membrane sterols and redox play a role in the ion channel activity of CLIC1. Full article

(This article belongs to the Special Issue Feature Papers)

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3267 KiB

Open AccessArticle

A Thin Film Nanocomposite Membrane with MCM-41 Silica Nanoparticles for Brackish Water Purification

by Mohammed Kadhom, Jun Yin and Baolin Deng

Membranes 2016, 6(4), 50; https://doi.org/10.3390/membranes6040050 - 6 Dec 2016

Cited by 47 | Viewed by 7094

Abstract

Thin film nanocomposite (TFN) membranes containing MCM-41 silica nanoparticles (NPs) were synthesized by the interfacial polymerization (IP) process. An m-phenylenediamine (MPD) aqueous solution and an organic phase with trimesoyl chloride (TMC) dissolved in isooctane were used in the IP reaction, occurring on [...] Read more.

Thin film nanocomposite (TFN) membranes containing MCM-41 silica nanoparticles (NPs) were synthesized by the interfacial polymerization (IP) process. An m-phenylenediamine (MPD) aqueous solution and an organic phase with trimesoyl chloride (TMC) dissolved in isooctane were used in the IP reaction, occurring on a nanoporous polysulfone (PSU) support layer. Isooctane was introduced as the organic solvent for TMC in this work due to its intermediate boiling point. MCM-41 silica NPs were loaded in MPD and TMC solutions in separate experiments, in a concentration range from 0 to 0.04 wt %, and the membrane performance was assessed and compared based on salt rejection and water flux. The prepared membranes were characterized via scanning electron microscopy (SEM), transmission electron microscopy (TEM), contact angle measurement, and attenuated total reflection Fourier transform infrared (ATR FT-IR) analysis. The results show that adding MCM-41 silica NPs into an MPD solution yields slightly improved and more stable results than adding them to a TMC solution. With 0.02% MCM-41 silica NPs in the MPD solution, the water flux was increased from 44.0 to 64.1 L/m²·h, while the rejection virtually remained the same at 95% (2000 ppm NaCl saline solution, 25 °C, 2068 kPa (300 psi)). Full article

(This article belongs to the Special Issue Feature Papers)

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4660 KiB

Open AccessArticle

Mass Transport through Nanostructured Membranes: Towards a Predictive Tool

by Siavash Darvishmanesh and Bart Van der Bruggen

Membranes 2016, 6(4), 49; https://doi.org/10.3390/membranes6040049 - 2 Dec 2016

Cited by 10 | Viewed by 5119

Abstract

This study proposes a new mechanism to understand the transport of solvents through nanostructured membranes from a fundamental point of view. The findings are used to develop readily applicable mathematical models to predict solvent fluxes and solute rejections through solvent resistant membranes used [...] Read more.

This study proposes a new mechanism to understand the transport of solvents through nanostructured membranes from a fundamental point of view. The findings are used to develop readily applicable mathematical models to predict solvent fluxes and solute rejections through solvent resistant membranes used for nanofiltration. The new model was developed based on a pore-flow type of transport. New parameters found to be of fundamental importance were introduced to the equation, i.e., the affinity of the solute and the solvent for the membrane expressed as the hydrogen-bonding contribution of the solubility parameter for the solute, solvent and membrane. A graphical map was constructed to predict the solute rejection based on the hydrogen-bonding contribution of the solubility parameter. The model was evaluated with performance data from the literature. Both the solvent flux and the solute rejection calculated with the new approach were similar to values reported in the literature. Full article

(This article belongs to the Special Issue Feature Papers)

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2873 KiB

Open AccessFeature PaperArticle

Hydrogen Induced Abrupt Structural Expansion at High Temperatures of a Ni₃₂Nb₂₈Zr₃₀Cu₁₀ Membrane for H₂ Purification

by Oriele Palumbo, Francesco Trequattrini, Madhura Hulyalkar, Suchismita Sarker, Narendra Pal, Dhanesh Chandra, Ted Flanagan, Michael Dolan and Annalisa Paolone

Membranes 2016, 6(4), 48; https://doi.org/10.3390/membranes6040048 - 21 Nov 2016

Cited by 4 | Viewed by 5164

Abstract

Ni-Nb-Zr amorphous membranes, prepared by melt-spinning, show great potential for replacing crystalline Pd-based materials in the field of hydrogen purification to an ultrapure grade (>99.999%). In this study, we investigate the temperature evolution of the structure of an amorphous ribbon with the composition [...] Read more.

Ni-Nb-Zr amorphous membranes, prepared by melt-spinning, show great potential for replacing crystalline Pd-based materials in the field of hydrogen purification to an ultrapure grade (>99.999%). In this study, we investigate the temperature evolution of the structure of an amorphous ribbon with the composition Ni₃₂Nb₂₈Zr₃₀Cu₁₀ (expressed in atom %) by means of XRD and DTA measurements. An abrupt structural expansion is induced between 240 and 300 °C by hydrogenation. This structural modification deeply modifies the hydrogen sorption properties of the membrane, which indeed shows a strong reduction of the hydrogen capacity above 270 °C. Full article

(This article belongs to the Special Issue Feature Papers)

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5049 KiB

Open AccessArticle

Preparation and Characterization of Hydrophilically Modified PVDF Membranes by a Novel Nonsolvent Thermally Induced Phase Separation Method

by Ningen Hu, Tonghu Xiao, Xinhai Cai, Lining Ding, Yuhua Fu and Xing Yang

Membranes 2016, 6(4), 47; https://doi.org/10.3390/membranes6040047 - 18 Nov 2016

Cited by 32 | Viewed by 9508

Abstract

In this study, a nonsolvent thermally-induced phase separation (NTIPS) method was first proposed to fabricate hydrophilically-modified poly(vinylidene fluoride) (PVDF) membranes to overcome the drawbacks of conventional thermally-induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) methods. Hydrophilically-modified PVDF membranes were successfully prepared by [...] Read more.

In this study, a nonsolvent thermally-induced phase separation (NTIPS) method was first proposed to fabricate hydrophilically-modified poly(vinylidene fluoride) (PVDF) membranes to overcome the drawbacks of conventional thermally-induced phase separation (TIPS) and nonsolvent-induced phase separation (NIPS) methods. Hydrophilically-modified PVDF membranes were successfully prepared by blending in hydrophilic polymer polyvinyl alcohol (PVA) at 140 °C. A series of PVDF/PVA blend membranes was prepared at different total polymer concentrations and blend ratios. The morphological analysis via SEM indicated that the formation mechanism of these hydrophilically-modified membranes was a combined NIPS and TIPS process. As the total polymer concentration increased, the tensile strength of the membranes increased; meanwhile, the membrane pore size, porosity and water flux decreased. With the PVDF/PVA blend ratio increased from 10:0 to 8:2, the membrane pore size and water flux increased. The dynamic water contact angle of these membranes showed that the hydrophilic properties of PVDF/PVA blend membranes were prominently improved. The higher hydrophilicity of the membranes resulted in reduced membrane resistance and, hence, higher permeability. The total resistance R_t of the modified PVDF membranes decreased significantly as the hydrophilicity increased. The irreversible fouling related to pore blocking and adsorption fouling onto the membrane surface was minimal, indicating good antifouling properties. Full article

(This article belongs to the Special Issue Feature Papers)

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2262 KiB

Open AccessFeature PaperArticle

Separation of Peptides with Forward Osmosis Biomimetic Membranes

by Niada Bajraktari, Henrik T. Madsen, Mathias F. Gruber, Sigurd Truelsen, Elzbieta L. Jensen, Henrik Jensen and Claus Hélix-Nielsen

Membranes 2016, 6(4), 46; https://doi.org/10.3390/membranes6040046 - 15 Nov 2016

Cited by 3 | Viewed by 6318

Abstract

Forward osmosis (FO) membranes have gained interest in several disciplines for the rejection and concentration of various molecules. One application area for FO membranes that is becoming increasingly popular is the use of the membranes to concentrate or dilute high value compound solutions [...] Read more.

Forward osmosis (FO) membranes have gained interest in several disciplines for the rejection and concentration of various molecules. One application area for FO membranes that is becoming increasingly popular is the use of the membranes to concentrate or dilute high value compound solutions such as pharmaceuticals. It is crucial in such settings to control the transport over the membrane to avoid losses of valuable compounds, but little is known about the rejection and transport mechanisms of larger biomolecules with often flexible conformations. In this study, transport of two chemically similar peptides with molecular weight (M_w) of 375 and 692 Da across a thin film composite Aquaporin Inside™ Membrane (AIM) FO membrane was investigated. Despite the relative large size, both peptides were able to permeate the dense active layer of the AIM membrane and the transport mechanism was determined to be diffusion-based. Interestingly, the membrane permeability increased 3.65 times for the 692 Da peptide (1.39 × 10⁻¹² m²·s⁻¹) compared to the 375 Da peptide (0.38 × 10⁻¹² m²·s⁻¹). This increase thus occurs for an 85% increase in Mw but only for a 34% increase in peptide radius of gyration (R_g) as determined from molecular dynamics (MD) simulations. This suggests that R_g is a strong influencing factor for membrane permeability. Thus, an increased R_g reflects the larger peptide chains ability to sample a larger conformational space when interacting with the nanostructured active layer increasing the likelihood for permeation. Full article

(This article belongs to the Special Issue Biological, Biomimetic, and Biomedical Applications of Membranes)

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3563 KiB

Open AccessArticle

Flux and Passage Enhancement in Hemodialysis by Incorporating Compound Additive into PVDF Polymer Matrix

by Qinglei Zhang, Xiaolong Lu, Qingzhao Zhang, Lei Zhang, Suoding Li and Shaobin Liu

Membranes 2016, 6(4), 45; https://doi.org/10.3390/membranes6040045 - 19 Oct 2016

Cited by 9 | Viewed by 5977

Abstract

In this study, Polyvinylidene fluoride (PVDF) hollow fiber hemodialysis membranes were prepared by non-solvent induced phase separation (NIPS) with compound addtive. The compound additive was made with polyvinyl pyrrolidone (PVP) and Poly ethylene glycol (PEG). The results showed that the modified PVDF membrane [...] Read more.

In this study, Polyvinylidene fluoride (PVDF) hollow fiber hemodialysis membranes were prepared by non-solvent induced phase separation (NIPS) with compound addtive. The compound additive was made with polyvinyl pyrrolidone (PVP) and Poly ethylene glycol (PEG). The results showed that the modified PVDF membrane had better separation performance than virgin PVDF membrane. The UF flux of modified PVDF membrane can reach 684 L·h⁻¹·m⁻² and lysozyme (LZM) passage is 72.6% while virgin PVDF membrane is 313 L·h⁻¹·m⁻² and 53.2%. At the same time, the biocompatibility of PVDF membranes was also improved. Compared with commercial polysulfone hemodialysis membrane (Fresenius F60S membrane), the modified PVDF membrane had better mechanical and separation performance. The stress and tensile elongation of modified PVDF membrane was 0.94 MPa and 352% while Fresenius F60S membrane was 0.79 MPa and 59%. The LZM passage reached 72.6% while Fresenius F60S membrane was 54.4%. It was proven that the modified PVDF membrane showed better hydrophilicity, antithrombogenicity, less BSA adsorption, and lower hemolytic ratio and adhesion of platelets. Water contact angle and BSA adsorption of the modified PVDF membrane are 38° and 45 mg/m² while Fresenius F60S membrane are 64° and 235 mg/m². Prothrombin time (PT) and activated partial thromboplastin time (APTT) of the modified PVDF membrane are 56.5 s and 25.8 s while Fresenius F60S membrane is 35.7 s and 16.6 s. However, further biocompatibility evaluation is needed to obtain a more comprehensive conclusion. Full article

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