Inorganic Membranes Research Articles

Application of modified cellulose-based antiscalant in reverse osmosis membrane scaling control

<p indent=0mm>Applying membrane scaling is a key problem in reverse osmosis (RO) desalination processes. By dosing antiscalant, we can effectively inhibit inorganic scale and control RO membrane scaling. Accordingly, in this work, an environmentally friendly modified cellulose-based antiscalant is synthesized by the etherification of cellulose and subsequent graft copolymerization using the etherification product carboxymethyl cellulose (CMC), acrylic acid (AA), and sodium allyl sulfonate (SAS): CMC-<italic>g</italic>-P(AA-<italic>co</italic>-SAS). The influence of molecular structure, CMC-<italic>g</italic>-P(AA-<italic>co</italic>-SAS) dose, and coexisting anions with respect to inhibiting the calcium-sulfate scale in the RO system are investigated. The results indicate that dosing CMC-<italic>g</italic>-P(AA-<italic>co</italic>-SAS) can significantly prolong the induction time of calcium-sulfate crystallization, inhibit the formation of calcium-sulfate scale, greatly alleviate both membrane fouling and membrane flux decline caused by membrane-surface scale formation, and effectively improve the membrane filtration efficiency. Static tests, scanning electron microscopy, optical microscopy, X-ray diffraction, conductivity measurements, and dispersion experiments suggest that the scale inhibition mechanism of CMC-<italic>g</italic>-P(AA-<italic>co</italic>-SAS) can be attributed to the chelation and dispersion effects of the introduced anionic groups, and that the carboxyl groups are more efficient in the inhibition of calcium-sulfate scale than the sulfonic groups. In addition, an appropriate number of sulfonic groups on the graft chain of CMC-<italic>g</italic>-P(AA-<italic>co</italic>-SAS) can improve the water solubility of CMC-<italic>g</italic>-P(AA-<italic>co</italic>-SAS), as well as effectively stabilize the scale-formed substances and enhance the scale inhibition efficiency. If the proportion of sulfonic groups is too high, the content of the carboxyl groups decreases accordingly, which reduces the chelation and dispersion effects of CMC-<italic>g</italic>-P(AA-<italic>co</italic>-SAS), which, in turn, reduces the scale inhibition performance.

Recent advancements in molecular separation of gases using microporous membrane systems: A comprehensive review on the applied liquid absorbents

Industrial-based molecular separation of detrimental gaseous molecules (especially CO2) from various mixtures using different types of chemical absorbents has been recently of paramount attention all around the world to mitigate their severe impacts on ecosystem such as acid rain and global warming. This paper aims to present a state-of-the-art review about the recent advancements in the molecular separation of CO2 applying hollow fiber membrane contactors (HFMCs). Additionally, all employed membrane materials for separating CO2 contaminant including polymeric membranes (PMs), microporous organic polymers (MOPs), fixed-site-carrier membranes (FSCMs), inorganic membranes (IMs), mixed matrix membranes (MMMs), and carbon molecular sieve membranes (CMSMs) are comprehensively discussed. Discussion about the most important operating challenges towards the separation of CO2 inside the HFMCs (i.e., mass transfer resistance and membrane pores wettability) is considered as another objective of this paper. Another aim of this paper is to classify the prevalent types of liquid absorbents and critically discuss the advantages and disadvantages of each group in the field of membrane-based gas separation process.

Recent Progress in a Membrane-Based Technique for Propylene/Propane Separation.

The similar physico-chemical properties of propylene and propane molecules have made the separation process of propylene/propane challenging. Membrane separation techniques show substantial prospects in propylene/propane separation due to their low energy consumption and investment costs, and they have been proposed to replace or to be combined with the conventional cryogenic distillation process. Over the past decade, organosilica membranes have attracted considerable attention due to their significant features, such as their good molecular sieving properties and high hydrothermal stability. In the present review, holistic insight is provided to summarize the recent progress in propylene/propane separation using polymeric, inorganic, and hybrid membranes, and a particular inspection of organosilica membranes is conducted. The importance of the pore subnano-environment of organosilica membranes is highlighted, and future directions and perspectives for propylene/propane separation are also provided.

Synthesis and preliminary gas permeation properties of vitreous composite clinoptilolite membranes

In this study, we communicate our initial findings regarding the development of novel inorganic composite clinoptilolite membranes. The membranes were formed from natural clinoptilolite microparticles sintered together using specialty glass atop a porous Al2O3 porous disk that was used as a support. Fourier transform infrared spectroscopy and x-ray diffraction analysis was used to confirm that the natural clinoptilolite used in this study maintains its overall structural conformation following heat treatment as high as 1073 K. Surface and cross-sectional scanning electron microscopy imagery of the prepared membranes showed the formation of a porous clinoptilolite – glass composite layer and a mostly glass layer with lesser porosity. Single gas He, CO2, CH4, and N2 permeation experiments were carried out to evaluate the initial performance parameters of the membranes. Single gas membrane permeation decreased with increasing amount of glass, and ranged from 2 × 10−7 mol/m2s Pa for the membrane prepared with 30 wt. % clinoptilolite as filler to as high as 4 × 10−6 mol/m2s Pa for the 50 wt. % clinoptilolite membrane. The ideal selectivity was calculated from the single gas permeance for potential natural gas or biogas CH4/N2 and CO2/CH4 separations. These values were the highest at 1.7 ± 0.2 and 1.9 ± 0.1 for the membranes prepared with 40 wt. % and 30 wt. % clinoptilolite, respectively. Considerable refinements to this technique are necessary in order to minimize the presence defects before it may be used as an alternative to inorganic membranes or mixed matrix membranes as an approach when zeolite crystallization is difficult to achieve.

Recent advances in synthesis and applications of mixed matrix membranes

Researchers are currently considering membranes separation processes due to their eco-friendly, process simplicity and high efficiency. Selecting a suitable and efficient operation is the primary concern of researchers in the field of separation industries. In recent decades, polymeric and inorganic membranes in the separation industry have made significant progress. The polymeric and inorganic membranes have been challenged due to their competitiveness in permeability and selectivity factors. A combination of nanoparticle fillers within the polymer matrix is an effective method to increase polymeric and inorganic membranes’ efficiency in separation processes. Mixed matrix membranes (MMMs) have been considered by the separation industry due to high mechanical and physicochemical, and transfer properties. Moreover, gas separation, oil treatment, heavy metal ions removal, water treatment and oil-water separation are common MMMs applications. Selecting suitable polymer blends and fillers is the key to the MMMs construction. The combination of rubbery and glassy polymers with close solubility parameters increases the MMMs performance. The filler type and synthesis methods also affect the morphological and transfer properties of MMMs significantly. Zeolites, graphene oxide (GO), nanosilica, carbon nanotubes (CNTs), zeolite imidazole frameworks (ZIFs) and metal-organic frameworks (MOFs) are used in the MMMs synthesis as fillers. Finally, solution mixing, polymerization in situ and sol-gel are the primary synthesising MMMs methods.

Design and operational considerations of catalytic membrane reactors for ammonia synthesis

AbstractProduction of ammonia using hydrogen derived from renewable electricity instead of hydrocarbon reforming would dramatically reduce the carbon footprint of this commodity chemical. Novel technologies such as catalytic membrane reactors (CMRs) may potentially be more compatible with distributed ammonia production than the conventional Haber–Bosch process. A reactor model is developed based on integrating a standard industrial iron catalyst into a CMR equipped with an inorganic membrane that is selective to NH3 over N2/H2. CMR performance is studied as functions of wide ranges of membrane properties and operating conditions. Conversion and ammonia recovery are dictated principally by the ammonia permeance, and the benefits by using membranes become significant above 100 GPU = 3.4 × 10−8 mol m−2 s−1 Pa−1. To be effective, the CMR requires a minimum selectivity for ammonia of 10 over both nitrogen and hydrogen and purity scales with the effective selectivity. Increasing the pressure of operation significantly improves all metrics, and at P = 30 bar with a quality membrane, ammonia is almost completely recovered, enabling direct recycle of unreacted hydrogen and nitrogen without need for recompression. Temperature drives conversion and scales monotonically without thermodynamic limitations in a CMR. Alternatively, the temperature may be reduced as low as 300°C while achieving conversion levels surpassing equilibrium limits at T = 400°C in a conventional reactor.

An investigation into the leaching of micro and nano particles and chemical pollutants from disposable face masks - linked to the COVID-19 pandemic

The production of disposable plastic face masks (DPFs) in China alone has reached to approximately 200 million a day, in a global effort to tackle the spread of the new SARS-CoV-2 virus. However, improper and unregulated disposals of these DPFs has been and will continue to intensify the plastic pollution problem we are already facing. This study focuses on the emission of pollutants from 7 DPF brands that were submerged in water to simulate environmental conditions if these DPFs were littered. The DPF leachates were filtered by inorganic membranes, and both particle-deposited organic membranes and the filtrates were characterized using techniques such as FTIR, SEM-EDX, Light Microscopy, ICP-MS and LC-MS. Micro and nano scale polymeric fibres, particles, siliceous fragments and leachable inorganic and organic chemicals were observed from all of the tested DPFs. Traces of concerning heavy metals (i.e. lead up to 6.79 µg/L) were detected in association with silicon containing fragments. ICP-MS also confirmed the presence of other leachable metals like cadmium (up to 1.92 µg/L), antimony (up to 393 µg/L) and copper (up to 4.17 µg/L). LC-MS analysis identified polar leachable organic species related to plastic additives and contaminants; polyamide-66 monomer and oligomers (nylon-66 synthesis), surfactant molecules, dye-like molecules and polyethylene glycol were all tentatively identified in the leachate. The toxicity of some of the chemicals found and the postulated risks of the rest of the present particles and molecules, raises the question of whether DPFs are safe to be used on a daily basis and what consequences are to be expected after their disposal into the environment.

Effects of membrane selectivity and configuration on methane purity and recovery from high carbon dioxide content natural gas

Many membranes for gas separation and purification reportedly exhibit carbon dioxide/methane selectivity of 2.6–37 for polymer membranes and as high as 42.65 for inorganic membranes. Researches on improving membrane selectivity appear to be on the rise because higher selectivity is thought to offer better carbon dioxide capture and removal. However, the present study demonstrates that a membrane, even with high carbon dioxide/methane selectivity of 750 with flow configuration of Type 1, could not enrich methane effectively from high carbon dioxide content natural gas to the purity level that meets the natural gas pipeline quality of 75%. Thus, the membrane is not suitable for application in some of Malaysian, Australian and Brazilian gas fields which contain extraordinarily high carbon dioxide. Results from the present study demonstrate that methane was successfully enriched to 81.41% in the permeate when membrane with methane/carbon dioxide selectivity of 1000 with flow configuration of Type 2 was used. This paper addresses the concern regarding the efficacy of high membrane selectivity in methane enrichment process from high carbon dioxide content natural gas and provides the necessary correlations, analyses, and suggestions.

Zeolite Composite Membranes with a Nanoporous Fluorinated Carbonaceous Sheath for Organic Solvent Filtration

Inorganic membranes for organic solvent nanofiltration (OSN) inherently rely on the chemical affinity of pores, in particular, hydrophobicity of the pores and pore functionalities, to reject small ...

Facile access to highly flexible and mesoporous structured silica fibrous membranes for tetracyclines removal

• Highly flexible and mesoporous silica nanofibrous membranes were fabricated. • The sample had large surface area (147.51 m 2 g −1 ) and pore volume (0.336 cm 3 g −1 ). • The maximum adsorption capacity of MPSNMs towards TCH was 53.29 mg g −1 . • TCH sorption capacity showed a linear relationship ( R 2 = 0.985) to mesopore volume. • Deduced binding mechanism was hydrogen bonding and electrostatic interaction. Ceramic-based porous fibers, benefitting from their high specific surface area, and superior thermal stability as well as chemical durability, are highly desirable for efficient tetracyclines removal from wastewater. However, the current ceramic porous fibers are commonly fragile with poor recyclability during application. Here, facile access to mesoporous structured silica nanofibrous membranes (MPSNMs) with superior flexibility, high specific surface area, and large mesopore volume is provided, that is, using phase separation-driven electrospinning technique and subsequent calcination processing. The obtained single mesoporous silica nanofiber could be circularly folded into half without any fracturing, which is comparable to the bending behavior of flexible polymer-based material. The resultant MPSNMs exhibited superior adsorption capability towards tetracycline hydrochloride (TCH) and outstanding recyclability, and the capacity could reach 53.29 mg g −1 , which is more superior to most of the currently reported inorganic-based adsorbents. Furthermore, based on the calculated results of reduced density gradient (RDG) analysis and non-covalent interaction (NCI) isosurfaces, the adsorption mechanism could be the synergetic effects of hydrogen-bonding interactions and electrostatic attraction between TCH and MPSNMs. This work not only enlightens the preparation of flexible mesoporous inorganic nanofibrous membranes but also provides a reference for designing and developing new kinds of adsorbents for various fields.

Preparation, characterization and application of geopolymer-based tubular inorganic membrane

Inorganic membrane (IM) has been widely concerned in the fields of water filtration and gas treatment. Compared to ceramic and organic membrane, geopolymer inorganic membrane (Geo-IM) has a good application prospect in many fields due to their low cost and excellent properties. In this paper, a green, environmental-friendly, fine performance and controllable pore structure tubular inorganic membrane prepared by using cheap slag reinforced metakaolin based geopolymer can be used for water filtration and flue-gas treatment. The experimental results show that the compressive strength and flexural strength of the sodium based Geo-IM are increasing from 7 MPa and 1.37 MPa to 14 MPa and 2.12 MPa respectively. In other word, the compressive strength and flexural strength of potassium based Geo-IM were increased by 100% and 54.74% respectively compared with that of sodium based Geo-IM, it is helpful for the inorganic membrane to withstand certain pressure. The thermogravimetric (TG) analysis showed that the potassium based Geo-IM has good thermal stability. By measuring the compressive strength of the IM at 0–1000 °C, it can be seen that the potassium-based inorganic membrane (K-WG-IM) can withstand the temperature of 800 °C. The specific surface area of K-WG-IM is about 77 m2·g−1, the porosity is about 70%, and the water flux is 100–8000 kg·m−2·h−1 (25 °C, 1 MPa). The filtration performance of the Geo-IM was characterized by the self-made water filtration and flue-gas treatment device in the laboratory. It is found that the Geo-IM could capture particulate matter (PM) with particle size greater than 1.67 μm in carbon black aqueous solution, and the removal rate of PM2.5 in flue-gas was as high as 97%, and the removal rate was still above 90% when the flue-gas temperature reached 600 °C. In a word, the tubular Geo-IM with low-cost, high-efficient and green properties has considerable potential in the practical applications.

Hydrophobic Two-Dimensional MoS2 Nanosheets Embedded in a Polyether Copolymer Block Amide (PEBA) Membrane for Recovering Pyridine from a Dilute Solution.

A two-dimensional molybdenum disulfide (MoS2) nanosheet, as a new type of inorganic material with high hydrophobicity and excellent physicochemical stability, holds great application potential in the preparation of a high separation performance organic–inorganic hybrid membrane. In this work, high hydrophobic MoS2 was embedded in hydrophobic polyether copolymer block amide (PEBA) to prepare PEBA/MoS2 organic–inorganic hybrid membranes. The structure, morphology, and hydrophobicity of the hybrid membrane were characterized by scanning electron microscopy, thermogravimetric analysis, contact angle goniometry, X-ray diffraction, infrared spectroscopy analysis, and atomic force microscopy. The effect of embedding of MoS2 on the swelling degree and pervaporation separation performance of the PEBA/MoS2 hybrid membrane was studied with a 1.0 wt % pyridine dilute solution. The results indicated that with increasing the MoS2 content, the separation factor of PEBA/MoS2 increased first and then decreased, while it showed a downward trend in the permeation flux. When the MoS2 content in the PEBA/MoS2 hybrid membrane was 10.0 wt %, the permeation flux was 83.4 g m–2 h–1 (decreased by 21.5% compared with the pure PEBA membrane), and the separation factor reached a maximum value of 11.11 (increased by 37.6% compared with the pure PEBA membrane). Meanwhile, the effects of feed temperature on the pervaporation separation performance of PEBA/MoS2 hybrid membranes were also studied. In addition, as the PEBA/MoS2 hybrid membrane has excellent thermal stability, it is expected to be a promising material for recovering pyridine from wastewater.

Improvement of the fabricated and application of aluminosilicate-based microfiltration membrane

Aluminosilicate composite materials are characterized by their low cost, nontoxicity and facilely shaped. Membrane prepared using aluminosilicate composites have the following disadvantages: large mean pore size and low mechanical strength. To address these limitations, flat microfiltration membranes were fabricated using SiO2 powder and aluminosilicate composite as raw materials. The membrane performance was optimized by regulating the particle size of SiO2, the ratio of SiO2 to aluminosilicate composite (s/a), and the type of chemical admixture. The X-ray diffraction results indicated that the crystalline SiO2 particles were favorable for the preparation of membranes with higher bending strengths. The decreasing particle sizes of SiO2 (1.33–0.15 μm) decreased the pore size distribution. The bending strength of the membrane reduced with an increase in s/a, while was effectively enhanced by adding dissolved Na2SiO3. The optimized inorganic microfiltration membrane could also catalyze ozone to remove 100% of benzophenone-4 with an initial concentration of 10 mg L−1 within 15 min, and TOC removal by 52.67%. This paper presents a revised method for preparing an inorganic microfiltration membrane, which is an increasingly promising material for water treatment because of its low cost, low energy consumption, and high catalytic performance.

Modelling the Molecular Permeation through Mixed-Matrix Membranes Incorporating Tubular Fillers.

Membrane-based processes are considered a promising separation method for many chemical and environmental applications such as pervaporation and gas separation. Numerous polymeric membranes have been used for these processes due to their good transport properties, ease of fabrication, and relatively low fabrication cost per unit membrane area. However, these types of membranes are suffering from the trade-off between permeability and selectivity. Mixed-matrix membranes, comprising a filler phase embedded into a polymer matrix, have emerged in an attempt to partly overcome some of the limitations of conventional polymer and inorganic membranes. Among them, membranes incorporating tubular fillers are new nanomaterials having the potential to transcend Robeson’s upper bound. Aligning nanotubes in the host polymer matrix in the permeation direction could lead to a significant improvement in membrane permeability. However, although much effort has been devoted to experimentally evaluating nanotube mixed-matrix membranes, their modelling is mostly based on early theories for mass transport in composite membranes. In this study, the effective permeability of mixed-matrix membranes with tubular fillers was estimated from the steady-state concentration profile within the membrane, calculated by solving the Fick diffusion equation numerically. Using this approach, the effects of various structural parameters, including the tubular filler volume fraction, orientation, length-to-diameter aspect ratio, and permeability ratio were assessed. Enhanced relative permeability was obtained with vertically aligned nanotubes. The relative permeability increased with the filler-polymer permeability ratio, filler volume fraction, and the length-to-diameter aspect ratio. For water-butanol separation, mixed-matrix membranes using polydimethylsiloxane with nanotubes did not lead to performance enhancement in terms of permeability and selectivity. The results were then compared with analytical prediction models such as the Maxwell, Hamilton-Crosser and Kang-Jones-Nair (KJN) models. Overall, this work presents a useful tool for understanding and designing mixed-matrix membranes with tubular fillers.

Novel oxygen permeable hollow fiber perovskite membrane with surface wrinkles

Oxygen permeable ceramic hollow fiber perovskite membranes could be applied as the micro-membrane reactors for high temperature oxidations to integrate air separation and reaction in same unit. Membrane reactors normally require the loading of extra catalyst. However, how to anchor the catalysts in these hollow fiber structured reactors along the surface is a big issue. In this work, the synthesis and properties of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) hollow fiber perovskite membranes with wrinkled surface was reported. This article demonstrates its applicability for oxygen separation from air, before and after Ag deposition as the catalyst in the wrinkles of the hollow fibers. The wrinkled membranes display the oxygen permeation flux of 0.62 (prior to Ag deposition) and 1.48 (after Ag loading) mL·min−1·cm−2 operated at 950 °C, which is 1.2 and 3.0 times the permeation flux of membranes without wrinkles, respectively. This research contributes a novel inorganic hollow fiber membrane with wrinkled surfaces as the catalyst bed for industrial applications.

Review on membrane technology for separation of biodiesel

This article is focused on the separation of biodiesel from glycerol using membrane technology; it addresses the polymeric and inorganic membrane used for the separation of biodiesel as well as the development of the membrane reactor for the separation of biodiesel. The modified membrane reactor could enhance the chemical and physical properties of the membrane, boosting the separation quality while reducing cost. The energy requirement has increased due to an increase in the population. Natural energy resources are not sufficient to meet the requirements of an increase in population. Thus, it is imperative to look at alternative energy sources such as biodiesel. Biodiesel is biodegradable, sustainable, and clean energy. It is critical to separate biodiesel from impurities by international standards. Membrane technology has yielded significant results in the separation of biodiesel. It is environmentally friendly and reduces water loss and scarcity.

Fabrication and characterization of poly(ether-block-amide) (Pebax-1657) and silicoaluminophosphate (SAPO-34) composite membranes

In the past few years, composite membrane has been introduced to cater the limitation of polymeric and inorganic membranes. However, the fabrication of ideal composite membrane with appropriate loading of filler remains challenging. Thus, the material selection as well as optimum loading with the conditions observed for the formulation of the composite membrane studied. In this present work, a series of poly(ether-block-amide) (Pebax-1657) and silicoaluminophosphate (SAPO-34) composite membrane with different loading of SAPO-34 particles (0–4 wt%) were fabricated. The physicochemical properties of the resultant membranes were investigated by utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). Based on analysis, a good distribution of filler was obtained for the membranes loaded with 1 wt% and 2 wt% of SAPO-34 particles. Further increase of inorganic filler loading lead to the sedimentation and agglomeration of particle in the membrane, which may deteriorate the membrane performance in gas separation. Therefore, the optimum loading of inorganic particles in polymer phase play a major role in obtaining membrane with minimum defects ahead of gas separation performance tests such as for CO2/ethylene separation application.

Graphenylene and inorganic graphenylene nanopores for gas-phase 4He/3He separation: kinetic and steady-state considerations.

Selective membrane-based separation of light isotopes is considered to be possible based on the quantum phenomena. In this regard, the role of two mass-dependent effects, quantum tunneling and zero-point energy (ZPE), is realized to be consequential for selective separation of helium isotopes using appropriate membranes. In the present study, the efficiency of two analogous nanoporous membranes, graphenylene (GP) and inorganic graphenylene (IGP), for gas phase separation of 3He and 4He has been theoretically investigated. Since the performance of the studied membranes is extremely influenced by the close competition between both quantum tunneling and zero-point energy (ZPE) effects, high precision in the calculations is required to provide more realistic theoretical predictions. The current study attempts to provide such predictions by applying domain-based local pair natural orbital coupled cluster theory (DLPNO-CCSD) to obtain the accurate helium-pore interaction potential, based on which the tunneling rates, as well as the exact (anharmonic) bound levels for the vibration of helium in the pore plane, are calculated. From the analysis of the obtained results, the performance of the GP and IGP nanopores has been investigated in both kinetic competition and steady-state conditions in the temperature range of 10-200 K. The results of this study indicate that harmonic oscillator approximation significantly overestimates the efficiency of the studied nanopores for helium isotope separation. Based on our accurate calculations, both GP and IGP nanopores provide almost similar selectivities in kinetic competition conditions (Stot4/3 ≈ 3 at T = 50 K); however, the predicted permeance for GP (10-8 mol m-2 s-1 bar-1) is about 100 times higher than that predicted for IGP under the same conditions. Under steady-state conditions, IGP has been shown to be more efficient than GP, since it provides acceptable values of separation factor at higher temperatures.

Preparation, characterization and electrical conductance studies of inorganic precipitate parchment supported barium molybdate membrane

Barium molybdate parchment impregnated inorganic precipitate membrane was fabricated by the ion-interaction method. The electrical conductance across the newly prepared membrane in contact with different uni-univalent salts at various temperatures (10°C to 50°C) have been measured. The thermodynamic activation parameters like Ea, ΔH≠, ΔG≠ and ΔS≠ have also been measured. The prepared membrane was characterized by SEM, TEM, FTIR, TGA/DTA, XRD and EDX analysis. The antibacterial activity of synthetic membrane was studied against Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus by the agar well diffusion method.

Vapor-Induced Pore-Forming Method for Fabricating High-Flux Inorganic Microfiltration Membranes by Atmospheric Plasma Spraying

Vapor-Induced Pore-Forming Method for Fabricating High-Flux Inorganic Microfiltration Membranes by Atmospheric Plasma Spraying