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2 pages, 178 KiB

Open AccessEditorial

Nanomaterials for Membranes, Membrane Reactors, and Catalyst Systems

by Gheorghe Nechifor

Nanomaterials 2022, 12(6), 964; https://doi.org/10.3390/nano12060964 - 14 Mar 2022

Viewed by 1220

Abstract

Membranes are selective and highly productive nanostructures dedicated to developing separation, concentration, and purification processes with uses in the most diverse economic and social fields: industry, agriculture, transport, environment, health, and space exploration [...] Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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9 pages, 2579 KiB

Open AccessEditor’s ChoiceArticle

The Applications of Ultra-Thin Nanofilm for Aerospace Advanced Manufacturing Technology

by Guibai Xie, Hongwu Bai, Guanghui Miao, Guobao Feng, Jing Yang, Yun He, Xiaojun Li and Yun Li

Nanomaterials 2021, 11(12), 3282; https://doi.org/10.3390/nano11123282 - 03 Dec 2021

Cited by 11 | Viewed by 2140

Abstract

With the development of industrial civilization, advanced manufacturing technology has attracted widespread concern, including in the aerospace industry. In this paper, we report the applications of ultra-thin atomic layer deposition nanofilm in the advanced aerospace manufacturing industry, including aluminum anti-oxidation and secondary electron [...] Read more.

With the development of industrial civilization, advanced manufacturing technology has attracted widespread concern, including in the aerospace industry. In this paper, we report the applications of ultra-thin atomic layer deposition nanofilm in the advanced aerospace manufacturing industry, including aluminum anti-oxidation and secondary electron suppression, which are critical in high-power and miniaturization development. The compact and uniform aluminum oxide film, which is formed by thermal atomic layer deposition (ALD), can prevent the deep surface oxidation of aluminum during storage, avoiding the waste of material and energy in repetitive production. The total secondary electron yield of the C/TiN component nanofilm, deposited through plasma-enhanced atomic layer deposition, decreases 25% compared with an uncoated surface. The suppression of secondary electron emission is of great importance in solving the multipactor for high-power microwave components in space. Moreover, the controllable, ultra-thin uniform composite nanofilm can be deposited directly on the complex surface of devices without any transfer process, which is critical for many different applications. The ALD nanofilm shows potential for promoting system performance and resource consumption in the advanced aerospace manufacturing industry. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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17 pages, 5379 KiB

Open AccessArticle

Synthesis of SAPO-34 Nanoplates with High Si/Al Ratio and Improved Acid Site Density

by Syed Fakhar Alam, Min-Zy Kim, Aafaq ur Rehman, Devipriyanka Arepalli, Pankaj Sharma and Churl Hee Cho

Nanomaterials 2021, 11(12), 3198; https://doi.org/10.3390/nano11123198 - 25 Nov 2021

Cited by 4 | Viewed by 2009

Abstract

Two-dimensional SAPO-34 molecular sieves were synthesized by microwave hydrothermal process. The concentrations of structure directing agent (SDA), phosphoric acid, and silicon in the gel solution were varied and their effect on phase, shape, and composition of synthesized particles was studied. The synthesized particles [...] Read more.

Two-dimensional SAPO-34 molecular sieves were synthesized by microwave hydrothermal process. The concentrations of structure directing agent (SDA), phosphoric acid, and silicon in the gel solution were varied and their effect on phase, shape, and composition of synthesized particles was studied. The synthesized particles were characterized by various techniques using SEM, XRD, BET, EDX, and NH₃-TPD. Various morphologies of particles including isotropic, hyper rectangle, and nanoplates were obtained. It was found that the Si/Al ratio of the SAPO-34 particles was in a direct relationship with the density of acid sites. Moreover, the gel composition and preparation affected the chemistry of the synthesized particles. The slow addition of phosphoric acid improved the homogeneity of synthesis gel and resulted in SAPO-34 nanoplates with high density of acid sites, 3.482 mmol/g. The SAPO-34 nanoplates are expected to serve as a high performance catalyst due to the low mass transfer resistance and the high density of active sites. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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24 pages, 7460 KiB

Open AccessArticle

Osmium Nanoparticles-Polypropylene Hollow Fiber Membranes Applied in Redox Processes

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

Nanomaterials 2021, 11(10), 2526; https://doi.org/10.3390/nano11102526 - 27 Sep 2021

Cited by 11 | Viewed by 2161

Abstract

Composite membranes play a very important role in the separation, concentration, and purification processes, but especially in membrane reactors and membrane bioreactors. The development of composite membranes has gained momentum especially through the involvement of various nanoparticles, polymeric, oxide, or metal, that have [...] Read more.

Composite membranes play a very important role in the separation, concentration, and purification processes, but especially in membrane reactors and membrane bioreactors. The development of composite membranes has gained momentum especially through the involvement of various nanoparticles, polymeric, oxide, or metal, that have contributed to increasing their reactivity and selectivity. This paper presents the preparation and characterization of an active metal nanoparticle-support polymer type composite membrane, based on osmium nanoparticles obtained in situ on a polypropylene hollow fiber membrane. Osmium nanoparticles are generated from a solution of osmium tetroxide in tert-butyl alcohol by reduction with molecular hydrogen in a contactor with a polypropylene membrane. The composite osmium-polypropylene hollow fiber obtained membranes (Os-PPM) were characterized from the morphological and structural points of view: scanning electron microscopy (SEM), high resolution SEM (HR-SEM), energy dispersive spectroscopy analysis (EDAX), X-ray diffraction analysis (XRD), Fourier transform Infrared (FTIR) spectroscopy, thermal gravimetric analysis, and differential scanning calorimetry (TGA, DSC). The process performance was tested in a redox process of p-nitrophenol and 10-undecylenic (10-undecenoic) acid, as a target substance of biological or biomedical interest, in solutions of lower aliphatic alcohols in a membrane contactor with a prepared composite membrane. The characteristics of osmium nanoparticles-polypropylene hollow fiber membranes open the way to biological and biotechnological applications. These membranes do not contaminate the working environment, operate at relatively low temperatures, provide a large contact area between reactants, allow successive oxidation and reduction operations in the same module, and help to recover the reaction mass by ultrafiltration. The results obtained show that the osmium-polypropylene composite membrane allows the reduction of p-nitrophenol or the oxidation of 10-undecylenic acid, the conversion depending on the concentration in the lower aliphatic alcohol, the nature of the lower aliphatic alcohol, and the oxidant or reducing flow through the membrane contactor. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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14 pages, 2813 KiB

Open AccessArticle

Two-Dimensional MFI Zeolite Nanosheets Exfoliated by Surfactant Assisted Solution Process

by Aafaq ur Rehman, Devipriyanka Arepalli, Syed Fakhar Alam, Min-Zy Kim, Jungkyu Choi and Churl Hee Cho

Nanomaterials 2021, 11(9), 2327; https://doi.org/10.3390/nano11092327 - 07 Sep 2021

Cited by 10 | Viewed by 3128

Abstract

Two-dimensional (2D) zeolite nanosheets are important for the synthesis of high flux zeolite membranes due to their lateral size in a preferred orientation. A way to obtain 2D zeolite nanosheets is to exfoliate interlocked structures generated during the hydrothermal synthesis. The mechanical and [...] Read more.

Two-dimensional (2D) zeolite nanosheets are important for the synthesis of high flux zeolite membranes due to their lateral size in a preferred orientation. A way to obtain 2D zeolite nanosheets is to exfoliate interlocked structures generated during the hydrothermal synthesis. The mechanical and polymer assisted exfoliation process leads to mechanical damage in nanosheets and short lateral size. In the present study, polyvinylpyrrolidone (PVP) was introduced as an exfoliation agent and dispersant, so that multilamellar interlocked silicalite-1 zeolite nanosheets successfully exfoliated into a large lateral size (individual nanosheets 500~1200 nm). The good exfoliation behavior was due to the strong penetration of PVP into multilamellar nanosheets. Sonication assisted by mild milling helps PVP molecules to penetrate through the lamellar structure, contributing to the expansion of the distance between adjacent layers and thus decreasing the interactions between each layer. In addition, the stability of exfoliated nanosheets was evaluated with a series of organic solvents. The exfoliated nanosheets were well dispersed in n-butanol and stable for 30 days. Therefore, the PVP-assisted solution-based exfoliation process provides high aspect ratio MFI zeolite nanosheets in organic solvents for a long period. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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22 pages, 14874 KiB

Open AccessArticle

Prevention in Thermal Crack Formation in Chabazite (CHA) Zeolite Membrane by Developing Thin Top Zeolite and Thick Intermediate Layers

by Min-Zy Kim, Syed Fakhar Alam, Devipriyanka Arepalli, Aafaq ur Rehman, Won-Youl Choi and Churl-Hee Cho

Nanomaterials 2021, 11(8), 2113; https://doi.org/10.3390/nano11082113 - 19 Aug 2021

Cited by 9 | Viewed by 2322

Abstract

Chabazite (CHA) zeolite membranes with an intermediate layer of various thicknesses were prepared using planetary-milled seeds with an average particle diameter of 300, 250, 200, 140, and 120 nm. The 120 nm seed sample also contained several smaller particles with a diameter of [...] Read more.

Chabazite (CHA) zeolite membranes with an intermediate layer of various thicknesses were prepared using planetary-milled seeds with an average particle diameter of 300, 250, 200, 140, and 120 nm. The 120 nm seed sample also contained several smaller particles with a diameter of 20 nm. Such small seeds deeply penetrated into the pore channels of the α-alumina support during the vacuum-assisted infiltration process. During the secondary growth, the penetrated seeds formed a thick intermediate layer exiting between the zeolite layer and support. A decrease in seed size increased the penetration depth of seeds and the thickness of the intermediate layer, while the thickness of seed coating and zeolite layers was decreased. CHA zeolite membranes with a thin top zeoliate layer and a thick intermediate layer showed an excellent water/ethanol separation factor (>10,000) for 90 wt.% ethanol at 70 ℃ with a total flux of 1.5 kg m⁻² h⁻¹. There was no observation of thermal cracks/defects on the zeolite separation layer. The thick intermediate layer effectively suppressed the formation of thermal cracks during heating, since the tensile stress induced in the zeolite layer was well compensated by the compressive stress on the support. Therefore, it was successfully proven that controlling the microstructure of top surface and intermediate layers is an effective approach to improve the thermal stability of the CHA zeolite membrane. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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13 pages, 1461 KiB

Open AccessArticle

Encapsulation of Polyphenols from Lycium barbarum Leaves into Liposomes as a Strategy to Improve Their Delivery

by Ramona-Daniela Păvăloiu, Fawzia Sha’at, Georgeta Neagu, Mihaela Deaconu, Corina Bubueanu, Adrian Albulescu, Mousa Sha’at and Cristina Hlevca

Nanomaterials 2021, 11(8), 1938; https://doi.org/10.3390/nano11081938 - 28 Jul 2021

Cited by 16 | Viewed by 2729

Abstract

This study is focused on the encapsulation of polyphenols from Lycium barbarum leaves into liposomes as a strategy to improve their delivery. Liposomes loaded with Lycium barbarum leaves extract were obtained and characterized for particle size, polydispersity, entrapment efficiency, and stability. Liposomes presented [...] Read more.

This study is focused on the encapsulation of polyphenols from Lycium barbarum leaves into liposomes as a strategy to improve their delivery. Liposomes loaded with Lycium barbarum leaves extract were obtained and characterized for particle size, polydispersity, entrapment efficiency, and stability. Liposomes presented entrapment efficiency higher than 75%, nanometric particle size, narrow polydispersity, and good stability over three months at 4 °C. The liposomes containing Lycium barbarum offered a slower release of polyphenols with attenuated burst effect compared with the dissolution of free Lycium barbarum extract in phosphate buffer solution at pH 7.4. Moreover, an in vitro pretreatment of 24 h with loaded liposomes showed a cytoprotective effect against H₂O₂-induced cytotoxicity on L-929 mouse fibroblasts cells. These preliminary findings imply that liposomes could be successfully employed as carriers for polyphenols in pharmaceutical applications. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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14 pages, 4232 KiB

Open AccessFeature PaperArticle

Engineered Nanoparticles with Decoupled Photocatalysis and Wettability for Membrane-Based Desalination and Separation of Oil-Saline Water Mixtures

by Bishwash Shrestha, Mohammadamin Ezazi and Gibum Kwon

Nanomaterials 2021, 11(6), 1397; https://doi.org/10.3390/nano11061397 - 25 May 2021

Cited by 15 | Viewed by 2440

Abstract

Membrane-based separation technologies are the cornerstone of remediating unconventional water sources, including brackish and industrial or municipal wastewater, as they are relatively energy-efficient and versatile. However, membrane fouling by dissolved and suspended substances in the feed stream remains a primary challenge that currently [...] Read more.

Membrane-based separation technologies are the cornerstone of remediating unconventional water sources, including brackish and industrial or municipal wastewater, as they are relatively energy-efficient and versatile. However, membrane fouling by dissolved and suspended substances in the feed stream remains a primary challenge that currently prevents these membranes from being used in real practices. Thus, we directly address this challenge by applying a superhydrophilic and oleophobic coating to a commercial membrane surface which can be utilized to separate and desalinate an oil and saline water mixture, in addition to photocatalytically degrading the organic substances. We fabricated the photocatalytic membrane by coating a commercial membrane with an ultraviolet (UV) light-curable adhesive. Then, we sprayed it with a mixture of photocatalytic nitrogen-doped titania (N-TiO₂) and perfluoro silane-grafted silica (F-SiO₂) nanoparticles. The membrane was placed under a UV light, which resulted in a chemically heterogeneous surface with intercalating high and low surface energy regions (i.e., N-TiO₂ and F-SiO₂, respectively) that were securely bound to the commercial membrane surface. We demonstrated that the coated membrane could be utilized for continuous separation and desalination of an oil–saline water mixture and for simultaneous photocatalytic degradation of the organic substances adsorbed on the membrane surface upon visible light irradiation. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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22 pages, 5251 KiB

Open AccessEditor’s ChoiceArticle

Accessible Silver-Iron Oxide Nanoparticles as a Nanomaterial for Supported Liquid Membranes

by Ioana Alina Dimulescu (Nica), Aurelia Cristina Nechifor, Cristina Bǎrdacǎ (Urducea), Ovidiu Oprea, Dumitru Paşcu, Eugenia Eftimie Totu, Paul Constantin Albu, Gheorghe Nechifor and Simona Gabriela Bungău

Nanomaterials 2021, 11(5), 1204; https://doi.org/10.3390/nano11051204 - 01 May 2021

Cited by 25 | Viewed by 2489

Abstract

The present study introduces the process performances of nitrophenols pertraction using new liquid supported membranes under the action of a magnetic field. The membrane system is based on the dispersion of silver–iron oxide nanoparticles in n-alcohols supported on hollow microporous polypropylene fibers. The [...] Read more.

The present study introduces the process performances of nitrophenols pertraction using new liquid supported membranes under the action of a magnetic field. The membrane system is based on the dispersion of silver–iron oxide nanoparticles in n-alcohols supported on hollow microporous polypropylene fibers. The iron oxide–silver nanoparticles are obtained directly through cyclic voltammetry electrolysis run in the presence of soluble silver complexes ([AgCl₂]⁻; [Ag(S₂O₃)₂]³⁻; [Ag(NH₃)₂]⁺) and using pure iron electrodes. The nanostructured particles are characterized morphologically and structurally by scanning electron microscopy (SEM and HFSEM), EDAX, XRD, and thermal analysis (TG, DSC). The performances of the nitrophenols permeation process are investigated in a variable magnetic field. These studies show that the flux and extraction efficiency have the highest values for the membrane system embedding iron oxide–silver nanoparticles obtained electrochemically in the presence of [Ag(NH₃)₂]⁺ electrolyte. It is demonstrated that the total flow of nitrophenols through the new membrane system depends on diffusion, convection, and silver-assisted transport. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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24 pages, 9367 KiB

Open AccessArticle

Comparative Study of CoFe₂O₄ Nanoparticles and CoFe₂O₄-Chitosan Composite for Congo Red and Methyl Orange Removal by Adsorption

by Claudia Maria Simonescu, Alina Tătăruş, Daniela Cristina Culiţă, Nicolae Stănică, Ioana Alexandra Ionescu, Bogdan Butoi and Ana-Maria Banici

Nanomaterials 2021, 11(3), 711; https://doi.org/10.3390/nano11030711 - 12 Mar 2021

Cited by 45 | Viewed by 3107

Abstract

(1) Background: A comparative research study to remove Congo Red (CR) and Methyl Orange (MO) from single and binary solutions by adsorption onto cobalt ferrite (CoFe₂O₄) and cobalt ferrite–chitosan composite (CoFe₂O₄-Chit) prepared by a simple [...] Read more.

(1) Background: A comparative research study to remove Congo Red (CR) and Methyl Orange (MO) from single and binary solutions by adsorption onto cobalt ferrite (CoFe₂O₄) and cobalt ferrite–chitosan composite (CoFe₂O₄-Chit) prepared by a simple coprecipitation method has been performed. (2) Methods: Structural, textural, morphology, and magnetic properties of the obtained magnetic materials were examined by X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, N₂ adsorption–desorption analysis, Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), and magnetic measurements. The optimal operating conditions of the CR and MO removal processes were established in batch experiments. The mathematical models used to describe the processes at equilibrium were Freundlich and Langmuir adsorption isotherms. (3) Results: Cobalt ferrite–chitosan composite has a lower specific surface area (S_BET) and consequently a lower adsorption capacity than cobalt ferrite. CoFe₂O₄ and CoFe₂O₄–Chit particles exhibited a superparamagnetic behavior which enabled their efficient magnetic separation after the adsorption process. The research indicates that CR and MO adsorption onto prepared magnetic materials takes place as monolayer onto a homogeneous surface. According to Langmuir isotherm model that best fits the experimental data, the maximum CR/MO adsorption capacity is 162.68/94.46 mg/g for CoFe₂O₄ and 15.60/66.18 mg/g for CoFe₂O₄–Chit in single solutions. The results of the kinetics study revealed that in single-component solutions, both pseudo-first-order and pseudo-second-order kinetics models represent well the adsorption process of CR/MO on both magnetic adsorbents. In binary solutions, adsorption of CR/MO on CoFe₂O₄ better follows the pseudo-second-order kinetics model, while the kinetic of CR/MO adsorption on CoFe₂O₄–Chit is similar to that of the dyes in single-component solutions. Acetone and ethanol were successfully used as desorbing agents. (4) Conclusions: Our study revealed that CoFe₂O₄ and CoFe₂O₄–Chit particles are good candidates for dye-contaminated wastewater remediation. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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20 pages, 5451 KiB

Open AccessArticle

Control of Nanostructured Polysulfone Membrane Preparation by Phase Inversion Method

by Cristina Bărdacă Urducea, Aurelia Cristina Nechifor, Ioana Alina Dimulescu, Ovidiu Oprea, Gheorghe Nechifor, Eugenia Eftimie Totu, Ibrahim Isildak, Paul Constantin Albu and Simona Gabriela Bungău

Nanomaterials 2020, 10(12), 2349; https://doi.org/10.3390/nano10122349 - 26 Nov 2020

Cited by 32 | Viewed by 3879

Abstract

The preparation of membranes from polymer solutions by the phase inversion method, the immersion—precipitation technique has proved since the beginning of obtaining technological membranes the most versatile and simple possibility to create polymeric membrane nanostructures. Classically, the phase inversion technique involves four essential [...] Read more.

The preparation of membranes from polymer solutions by the phase inversion method, the immersion—precipitation technique has proved since the beginning of obtaining technological membranes the most versatile and simple possibility to create polymeric membrane nanostructures. Classically, the phase inversion technique involves four essential steps: Preparation of a polymer solution in the desired solvent, the formation of the polymer solution film on a flat support, the immersion of the film in a coagulation bath containing polymer solvents, and membrane conditioning. All phase inversion stages are important for the prepared membrane’s nanostructure and have been studied in detail for more than six decades. In this paper, we explored, through an electrochemical technique, the influence of the contact time with the polymer film’s environment until the introduction into the coagulation bath. The system chosen for membrane preparation is polysulfone-dimethylformamide-aqueous ethanol solution (PSf-DMF-EW). The obtained nanostructured membranes were characterized morphologically and structurally by scanning electron microscopy (SEM) and thermal analysis (TA), and in terms of process performance through water permeation and bovine serum albumin retention (BSA). The membrane characteristics were correlated with the polymeric film exposure time to the environment until the contact with the coagulation bath, following the diagram of the electrochemical parameters provided by the electrochemical technique. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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10 pages, 2768 KiB

Open AccessArticle

Disposable Stochastic Sensors Based on Nanolayer Deposition(s) of Silver and AgC Composite on Plastic for the Assay of α-amylase in Whole Blood and Saliva

by Raluca-Ioana Stefan-van Staden, Alexandrina Moscalu-Lungu and Marius Badulescu

Nanomaterials 2020, 10(8), 1528; https://doi.org/10.3390/nano10081528 - 04 Aug 2020

Cited by 7 | Viewed by 2187

Abstract

Nanolayer deposition(s) of Ag and AgC composite on a plastic substrate was used to design disposable stochastic sensors. Three shapes of nanocoatings were tested. The first shape was obtained by deposition of a nanofilm of Ag on the plastic material; the second shape [...] Read more.

Nanolayer deposition(s) of Ag and AgC composite on a plastic substrate was used to design disposable stochastic sensors. Three shapes of nanocoatings were tested. The first shape was obtained by deposition of a nanofilm of Ag on the plastic material; the second shape was obtained by deposition of a composite AgC nanolayer on the plastic material; the third shape was obtained by nanolayer deposition of a composite material of AgC on the top of the Ag nanofilm deposited on the plastic material. α-Cyclodextrin was used to modify the active surface of the sensor. Wide linear concentration ranges were obtained as follows: for de-assay of α-amylase in whole blood: 1.00 × 10⁻⁷–1.00 × 10³ U mL⁻¹ and for the assay of α-amylase in saliva: 1.5 × 10⁻¹⁵–1.5 × 10² U mL⁻¹. α-Amylase was reliably determined from whole blood and saliva samples using the proposed disposable stochastic sensors. Full article

(This article belongs to the Special Issue Nanomaterials for Membranes, Membrane Reactors and Catalyst Systems)

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