Membranes

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19 pages, 11288 KiB

Open AccessArticle

Phase Equilibria of the V-Ti-Fe System and Its Applications in the Design of Novel Hydrogen Permeable Alloys

by Yihao Wang, Limin Jia, Erhu Yan, Zhijie Guo, Shuo Zhang, Tangwei Li, Yongjin Zou, Hailiang Chu, Huanzhi Zhang, Fen Xu and Lixian Sun

Membranes 2023, 13(10), 813; https://doi.org/10.3390/membranes13100813 - 27 Sep 2023

Cited by 1 | Viewed by 1444

Abstract

The precise liquidus projection of the V-Ti-Fe system are crucial for designing high-performance hydrogen permeation alloys, but there are still many controversies in the research of this system. To this end, this article first uses the CALPHAD (CALculation of PHAse Diagrams) method to [...] Read more.

The precise liquidus projection of the V-Ti-Fe system are crucial for designing high-performance hydrogen permeation alloys, but there are still many controversies in the research of this system. To this end, this article first uses the CALPHAD (CALculation of PHAse Diagrams) method to reconstruct the alloy phase diagram and compares and analyses existing experimental data, confirming that the newly constructed phase diagram in this article has good reliability and accuracy. Second, this obtained phase diagram was applied to the subsequent development process of hydrogen permeation alloys, and the (Ti₆₅Fe₃₅)_100−xV_x (x = 0, 2.5, 5, 10, 15, 25) alloys with dual-phase {bcc-(V, Ti) + TiFe} structure were successfully explored. In particular, the alloys with x values equal to 2.5 at.% and 5 at.% exhibit relatively high hydrogen permeability. Third, to further increase the H₂ flux permeation through the alloys, a 500-mm-long tubular (Ti₆₅Fe₃₅)₉₅V₅ membrane for hydrogen permeation was prepared for the first time. Hydrogen permeation testing showed that this membrane had a very high H₂ flux (4.06 mL min⁻¹), which is ca. 6.7 times greater than the plate-like counterpart (0.61 mL min⁻¹) under the same test conditions. This work not only indicates the reliability of the obtained V-Ti-Fe phase diagram in developing new hydrogen permeation alloys, but also demonstrates that preparing tubular membranes is one of the most important means of improving H₂ flux. Full article

(This article belongs to the Special Issue Zeolitic Membranes for Gas and Liquid Separation: Synthesis and Applications)

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20 pages, 12066 KiB

Open AccessArticle

Phase Equilibria, Solidified Microstructure, and Hydrogen Transport Behaviour in the V-Ti-Co System

by Erhu Yan, Zhijie Guo, Limin Jia, Yihao Wang, Shuo Zhang, Tangwei Li, Yongjin Zou, Hailiang Chu, Huanzhi Zhang, Fen Xu and Lixian Sun

Membranes 2023, 13(9), 790; https://doi.org/10.3390/membranes13090790 - 12 Sep 2023

Cited by 1 | Viewed by 1312

Abstract

At present, the V-Ti-Co phase diagram is not established, which seriously hinders the subsequent development of this potential hydrogen permeation alloy system. To this end, this article constructed the first phase diagram of the V-Ti-Co system by using the CALculation of PHAse Diagrams [...] Read more.

At present, the V-Ti-Co phase diagram is not established, which seriously hinders the subsequent development of this potential hydrogen permeation alloy system. To this end, this article constructed the first phase diagram of the V-Ti-Co system by using the CALculation of PHAse Diagrams (CALPHAD) approach as well as relevant validation experiments. On this basis, hydrogen-permeable V_xTi₅₀Co_50−x (x = 17.5, 20.5, …, 32.5) alloys were designed, and their microstructure characteristics and hydrogen transport behaviour were further studied by XRD, SEM, EDS, and so on. It was found that six ternary invariant reactions are located in the liquidus projection, and the phase diagram is divided into eight phase regions by their connecting lines. Among them, some alloys in the TiCo phase region were proven to be promising candidate materials for hydrogen permeation. Typically, V_xTi₅₀Co_50−x (x = 17.5–23.5) alloys, which consist of the primary TiCo and the eutectic {bcc-(V, Ti) and TiCo} structure, show a high hydrogen permeability without hydrogen embrittlement. In particular, V_23.5Ti₅₀Co_26.5 exhibit the highest permeability of 4.05 × 10⁻⁸ mol H₂ m⁻¹s⁻¹Pa^−0.5, which is the highest value known heretofore in the V-Ti-Co system. The high permeability of these alloys is due in large part to the simultaneous increment of hydrogen solubility and diffusivity, and is closely related to the composition of hydrogen permeable alloys, especially the Ti content in the (V, Ti) phase. The permeability of this alloy system is much higher than those of Nb-TiCo and/or Nb-TiNi alloys. Full article

(This article belongs to the Special Issue Zeolitic Membranes for Gas and Liquid Separation: Synthesis and Applications)

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26 pages, 2595 KiB

Open AccessArticle

Role of Plasma Membrane at Dielectric Relaxations and Intermembrane Interaction in Human Erythrocytes

by Ivan T. Ivanov and Boyana K. Paarvanova

Membranes 2023, 13(7), 658; https://doi.org/10.3390/membranes13070658 - 11 Jul 2023

Cited by 1 | Viewed by 1513

Abstract

Dielectric relaxations at 1.4 MHz (β_sp) and 9 MHz (γ1_sp) on the erythrocyte spectrin network were studied by dielectric spectroscopy using dense suspensions of erythrocytes and erythrocyte ghost membranes, subjected to extraction with up to 0.2% volume Triton-X-100. The [...] Read more.

Dielectric relaxations at 1.4 MHz (β_sp) and 9 MHz (γ1_sp) on the erythrocyte spectrin network were studied by dielectric spectroscopy using dense suspensions of erythrocytes and erythrocyte ghost membranes, subjected to extraction with up to 0.2% volume Triton-X-100. The step-wise extraction of up to 60% of membrane lipids preserved γ1_sp and gradually removed β_sp-relaxation. On increasing the concentration up to 100 mM of NaCl at either side of erythrocyte plasma membranes, the β_sp-relaxation was linearly enhanced, while the strength of γ1_sp-relaxation remained unchanged. In media with NaCl between 100 and 150 mM β_sp-relaxation became slightly inhibited, while γ1_sp-relaxation almost disappeared, possibly due to the decreased electrostatic repulsion allowing erythrocytes to come into closer contact. When these media contained, at concentrations 10–30 mg/mL dextran (MW 7 kDa), polyethylene glycol or polyvinylpyrrolidone (40 kDa), or albumin or homologous plasma with equivalent concentration of albumin, the γ1_sp-relaxation was about tenfold enhanced, while β_sp-relaxation was strengthened or preserved. The results suggest the Maxwell–Vagner accumulation of ions on the lipid bilayer as an energy source for β_sp-relaxation. While β_sp-relaxation appears sensitive to erythrocyte membrane deformability, γ1_sp-relaxation could be a sensitive marker for the inter-membrane interactions between erythrocytes. Full article

(This article belongs to the Special Issue Zeolitic Membranes for Gas and Liquid Separation: Synthesis and Applications)

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14 pages, 4513 KiB

Open AccessArticle

A Facile Way to Fabricate GO-EDA/Al₂O₃ Tubular Nanofiltration Membranes with Enhanced Desalination Stability via Fine-Tuning the pH of the Membrane-Forming Suspensions

by Chunxiao Ding and Hong Qi

Membranes 2023, 13(5), 536; https://doi.org/10.3390/membranes13050536 - 22 May 2023

Cited by 2 | Viewed by 1643

Abstract

Pristine graphene oxide (GO)-based membranes have proven promising for molecular and ion separation owing to efficient molecular transport nanochannels, but their separation ability in an aqueous environment is limited by the natural swelling tendency of GO. To obtain a novel membrane with anti-swelling [...] Read more.

Pristine graphene oxide (GO)-based membranes have proven promising for molecular and ion separation owing to efficient molecular transport nanochannels, but their separation ability in an aqueous environment is limited by the natural swelling tendency of GO. To obtain a novel membrane with anti-swelling behavior and remarkable desalination capability, we used the Al₂O₃ tubular membrane with an average pore size of 20 nm as the substrate and fabricated several GO nanofiltration ceramic membranes with different interlayer structures and surface charges by fine-tuning the pH of the GO-EDA membrane-forming suspension (pH = 7, 9, 11). The resultant membranes could maintain desalination stability, whether immersed in water for 680 h or operated under a high-pressure environment. When the pH of the membrane-forming suspension was 11, the prepared GE-11 membrane showed a rejection of 91.5% (measured at 5 bar) towards 1 mM Na₂SO₄ after soaking in water for 680 h. An increase in the transmembrane pressure to 20 bar resulted in an increase in the rejection towards the 1 mM Na₂SO₄ solution to 96.3%, and an increase in the permeance to 3.7 L·m⁻²·h⁻¹·bar⁻¹. The proposed strategy in varying charge repulsion is beneficial to the future development of GO-derived nanofiltration ceramic membranes. Full article

(This article belongs to the Special Issue Zeolitic Membranes for Gas and Liquid Separation: Synthesis and Applications)

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21 pages, 19872 KiB

Open AccessArticle

Diffusion Barriers Minimizing the Strength Degradation of Reactive Air Brazed Ba_0.5Sr_0.5Co_0.8Fe_0.2O_3-δ Membranes during Aging

by Simone Herzog, Anke Kaletsch and Christoph Broeckmann

Membranes 2023, 13(5), 504; https://doi.org/10.3390/membranes13050504 - 10 May 2023

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Abstract

The separation of oxygen from air by means of inorganic ceramic membranes requires gas-tight ceramic–metal joints that enable reliable permeation operation in the oxygen partial pressure gradient at 850 °C. Reactive air brazing is a promising method to solve this challenge. However, reactive [...] Read more.

The separation of oxygen from air by means of inorganic ceramic membranes requires gas-tight ceramic–metal joints that enable reliable permeation operation in the oxygen partial pressure gradient at 850 °C. Reactive air brazing is a promising method to solve this challenge. However, reactive air brazed BSCF membranes suffer from a significant strength degradation that is caused by unhindered diffusion from the metal component during aging. In this study, we investigated how diffusion layers applied on the austenitic steel AISI 314 influence the bending strength of BSCF-Ag3CuO-AISI314 joints after aging. Three different approaches were compared as diffusion barriers: (1) aluminizing via pack cementation, (2) spray coating with NiCoCrAlReY, and (3) spray coating with NiCoCrAlReY and an additional 7YSZ top layer. Coated steel components were brazed to bending bars and aged for 1000 h at 850 °C in air prior to four-point bending and subsequent macroscopic as well microscopic analyses. In particular, coating with NiCoCrAlReY showed low-defect microstructures. The characteristic joint strength was raised from 17 MPa to 35 MPa after 1000 h aging at 850 °C. In addition, the dominant delamination fracture between the steel and the mixed oxide layer, observed in the reference series with uncoated steel, could be replaced by mixed and ceramic fractures of higher strength. The effect of residual joint stresses on the crack formation and path is analyzed and discussed. Chromium poisoning could no longer be detected in the BSCF, and interdiffusion through the braze was effectively reduced. Since the strength degradation of reactive air brazed joints is mainly caused by the metallic joining partner, the findings on the effect of the diffusion barriers in BSCF joints might be transferred to numerous other joining systems. Full article

(This article belongs to the Special Issue Zeolitic Membranes for Gas and Liquid Separation: Synthesis and Applications)

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Graphical abstract

13 pages, 18311 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Preparation and Lithium-Ion Separation Property of ZIF-8 Membrane with Excellent Flexibility

by Jun Zhao, Rongyu Fan, Shengchang Xiang, Jiapeng Hu and Ximing Zheng

Membranes 2023, 13(5), 500; https://doi.org/10.3390/membranes13050500 - 9 May 2023

Cited by 7 | Viewed by 2572

Abstract

Metal-organic framework (MOF) membranes exhibit immense potential for separation applications due to their regular pore channels and scalable pore sizes. However, structuring a flexible and high-quality MOF membrane remains a challenge due to its brittleness, which severely restricts its practical application. This paper [...] Read more.

Metal-organic framework (MOF) membranes exhibit immense potential for separation applications due to their regular pore channels and scalable pore sizes. However, structuring a flexible and high-quality MOF membrane remains a challenge due to its brittleness, which severely restricts its practical application. This paper presents a simple and effective method in which continuous, uniform, defect-free ZIF-8 film layers of tunable thickness are constructed on the surface of inert microporous polypropylene membranes (MPPM). To provide heterogeneous nucleation sites for ZIF-8 growth, an extensive amount of hydroxyl and amine groups were introduced on the MPPM surface using the dopamine-assisted co-deposition technique. Subsequently, ZIF-8 crystals were grown in-situ on the MPPM surface using the solvothermal method. The resultant ZIF-8/MPPM exhibited a lithium-ion permeation flux of 0.151 mol m⁻² h⁻¹ and a high selectivity of Li⁺/Na⁺ = 1.93, Li⁺/Mg²⁺ = 11.50. Notably, ZIF-8/MPPM has good flexibility, and the lithium-ion permeation flux and selectivity remain unchanged at a bending curvature of 348 m⁻¹. These excellent mechanical characteristics are crucial for the practical applications of MOF membranes. Full article

(This article belongs to the Special Issue Zeolitic Membranes for Gas and Liquid Separation: Synthesis and Applications)

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19 pages, 5213 KiB

Open AccessArticle

Efficient Pervaporation for Ethanol Dehydration: Ultrasonic Spraying Preparation of Polyvinyl Alcohol (PVA)/Ti₃C₂T_x Nanosheet Mixed Matrix Membranes

by Huijuan Tong, Qiao Liu, Nong Xu, Qing Wang, Long Fan, Qiang Dong and Aiqin Ding

Membranes 2023, 13(4), 430; https://doi.org/10.3390/membranes13040430 - 13 Apr 2023

Cited by 4 | Viewed by 2418

Abstract

Polyvinyl alcohol (PVA) pervaporation (PV) membranes have been extensively studied in the field of ethanol dehydration. The incorporation of two-dimensional (2D) nanomaterials into the PVA matrix can greatly improve the hydrophilicity of the PVA polymer matrix, thereby enhancing its PV performance. In this [...] Read more.

Polyvinyl alcohol (PVA) pervaporation (PV) membranes have been extensively studied in the field of ethanol dehydration. The incorporation of two-dimensional (2D) nanomaterials into the PVA matrix can greatly improve the hydrophilicity of the PVA polymer matrix, thereby enhancing its PV performance. In this work, self-made MXene (Ti₃C₂T_x-based) nanosheets were dispersed in the PVA polymer matrix, and the composite membranes were fabricated by homemade ultrasonic spraying equipment with poly(tetrafluoroethylene) (PTFE) electrospun nanofibrous membrane as support. Due to the gentle coating of ultrasonic spraying and following continuous steps of drying and thermal crosslinking, a thin (~1.5 μm), homogenous and defect-free PVA-based separation layer was fabricated on the PTFE support. The prepared rolls of the PVA composite membranes were investigated systematically. The PV performance of the membrane was significantly improved by increasing the solubility and diffusion rate of the membranes to the water molecules through the hydrophilic channels constructed by the MXene nanosheets in the membrane matrix. The water flux and separation factor of the PVA/MXene mixed matrix membrane (MMM) were dramatically increased to 1.21 kg·m⁻²·h⁻¹ and 1126.8, respectively. With high mechanical strength and structural stability, the prepared PGM-0 membrane suffered 300 h of the PV test without any performance degradation. Considering the promising results, it is likely that the membrane would improve the efficiency of the PV process and reduce energy consumption in the ethanol dehydration. Full article

(This article belongs to the Special Issue Zeolitic Membranes for Gas and Liquid Separation: Synthesis and Applications)

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19 pages, 6155 KiB

Open AccessArticle

In Situ Incorporation of TiO₂@Graphene Oxide (GO) Nanosheets in Polyacrylonitrile (PAN)-Based Membranes Matrix for Ultrafast Protein Separation

by Wei Zhou, Qiao Liu, Nong Xu, Qing Wang, Long Fan and Qiang Dong

Membranes 2023, 13(4), 377; https://doi.org/10.3390/membranes13040377 - 26 Mar 2023

Cited by 2 | Viewed by 1807

Abstract

Organic polymeric ultrafiltration (UF) membranes have been widely used in protein separation due to their advantages of high flux and simple manufacturing process. However, due to the hydrophobic nature of the polymer, pure polymeric UF membranes need to be modified or hybrid to [...] Read more.

Organic polymeric ultrafiltration (UF) membranes have been widely used in protein separation due to their advantages of high flux and simple manufacturing process. However, due to the hydrophobic nature of the polymer, pure polymeric UF membranes need to be modified or hybrid to increase their flux and anti-fouling performance. In this work, tetrabutyl titanate (TBT) and graphene oxide (GO) were simultaneously added to the polyacrylonitrile (PAN) casting solution to prepare a TiO₂@GO/PAN hybrid ultrafiltration membrane using a non-solvent induced phase separation (NIPS). During the phase separation process, TBT underwent a sol–gel reaction to generate hydrophilic TiO₂ nanoparticles in situ. Some of the generated TiO₂ nanoparticles reacted with the GO through a chelation interaction to form TiO₂@GO nanocomposites. The resulting TiO₂@GO nanocomposites had higher hydrophilicity than the GO. They could selectively segregate towards the membrane surface and pore walls through the solvent and non-solvent exchange during the NIPS, significantly improving the membrane’s hydrophilicity. The remaining TiO₂ nanoparticles were segregated from the membrane matrix to increase the membrane’s porosity. Furthermore, the interaction between the GO and TiO₂ also restricted the excessive segregation of the TiO₂ nanoparticles and reduced their losing. The resulting TiO₂@GO/PAN membrane had a water flux of 1487.6 L·m⁻²·h⁻¹ and a bovine serum albumin (BSA) rejection rate of 99.5%, which were much higher than those of the currently available UF membranes. It also exhibited excellent anti-protein fouling performance. Therefore, the prepared TiO₂@GO/PAN membrane has important practical applications in the field of protein separation. Full article

(This article belongs to the Special Issue Zeolitic Membranes for Gas and Liquid Separation: Synthesis and Applications)

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