Development Of New Membrane Materials Research Articles

Magnetic nanoparticle loading and application of weak magnetic field to reconstruct the cake layer of coagulation-ultrafiltration process to achieve efficient antifouling: Performance and mechanism analysis

Abandoning the costly development of new membrane materials and instead directly remodeling the naturally occurring cake layer constitutes a dynamic, low-cost, long-lasting, and proactive strategy to "fight fouling with fouling". Several optimization strategies, including coagulation/modified magnetic seed loading and applying a weak magnetic force (0.01T) at the ultrafiltration end, improved the anti-fouling, retention, and sieving performances of conventional ultrafiltration process during the treatment of source water having complex natural organic matter (NOMs) and small molecule micropollutants. Two modified magnetic seeds we prepared were composite nano-seed particles (Fe3O4@SiO2-NH2 (FS) and Fe3O4@SiO2@PAMAM-NH2 (FSP)). Aim of the study was to regulate the formation of cake layer via comprehensive testing of the antifouling properties of optimized processes and related mechanistic studies. It was found to be essential to enhance the interception of xanthate and tryptophan proteins in the cake layer for improving the anti-fouling performance based on the correlation and redundancy analyses, while the use of modified magnetic seeds and magnetic field showed a significant positive impact on water production. Blockage modeling demonstrated the ability to form a mature cake layer during the initial filtration stage swiftly. This mitigated the risk of irreversible fouling caused by pore blockage during the early stage of coagulation-ultrafiltration. Morphologically, the reconstructed cake layer exhibited elevated surface porosity, an internal cavity channel structure, and enhanced roughness that can promote increased water flux and retention of water impurities. These optimized the maturity of the cake layer in both time and space. Density Functional Theory (DFT), Extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, and Modified Extended Derjaguin-Landau-Verwey-Overbeek (MDLVO) calculations indicated aggregation behavior of matter on the cake layer to be enhanced effectively due to magnetic seed loading. This is mainly due to the strengthening of polar interactions, including hydrogen bonding, π-π* conjugation, etc., which can happen between the cake layer loaded with FSP and the organic matter. Under the influence of a magnetic field, magnetic force energy (VMF) significantly impacts the system by eliminating energy barriers. This research will provide innovative strategies for effectively purifying intricate source water through ultrafiltration while controlling membrane fouling.

Design Strategies for Forward Osmosis Membrane Substrates with Low Structural Parameters-A Review.

This article reviews the many innovative strategies that have been developed to specifically design the support layers of forward osmosis (FO) membranes. Forward osmosis (FO) is one of the most viable separation technologies to treat hypersaline wastewater, but its successful deployment requires the development of new membrane materials beyond existing desalination membranes. Specifically, designing the FO membrane support layers requires new engineering techniques to minimize the internal concentration polarization (ICP) effects encountered in cases of FO. In this paper, we have reviewed several such techniques developed by different research groups and summarized the membrane transport properties corresponding to each approach. An important transport parameter that helps to compare the various approaches is the so-called structural parameter (S-value); a low S-value typically corresponds to low ICP. Strategies such as electrospinning, solvent casting, and hollow fiber spinning, have been developed by prior researchers-all of them aimed at lowering this S-value. We also reviewed the quantitative methods described in the literature, to evaluate the separation properties of FO membranes. Lastly, we have highlighted some key research gaps, and provided suggestions for potential strategies that researchers could adopt to enable easy comparison of FO membranes.

Preparation of highly permeable nanofiltration membranes with interfacially polymerized biomonomers

To enable the wide application of nanofiltration (NF) membranes to increase the fresh water supply, the development of new membrane materials and preparation techniques are still highly desired. In this work, thin-film composite (TFC) NF membranes were fabricated via interfacial polymerization (IP) using three different kinds of biomonomers with trimesoyl chloride (TMC) on a polysulfone (PSf) substrate. Biomonomers such as dopamine hydrochloride (PDA), norepinephrine (PNE), and tannic acid (TA) are highly hydrophilic and environmentally friendly. Moreover, these materials can not only strongly adhere to substrates but can also form chemically stable cross-linked networks. The influence of these monomers on the formation of the selective layer was systematically investigated. Furthermore, a series of characterization techniques, including attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), zeta potential measurement, molecular weight cutoff (MWCO), X-ray photoelectron spectroscopy (XPS) and separation performance experiments, were used to study the properties of the TFC NF membranes. Biomonomer-based TFC NF membrane exhibited a higher water permeability of 8.14 L/m2 h bar with a high rejection for divalent ions (Na2SO4) of 93% compared to TFC NF membranes.

Fabrication and characterization of composite (nano)polyaniline/polyimide membrane for pervaporative separation of 1-octene/benzene mixtures

The variation of modern separation technology of aromatics/aliphatics mixture is membrane process and development of new membrane materials (polymeric and composite) for high efficiency. Nano-polyaniline has been prepared by bulk polymerisation method and is used for the fabrication of (nano)polyaniline/polyimide ((nano)PANI/PI) composite membrane to achieve pervaporative separation of 1-octene/benzene mixture. Benzene is carcinogenic compound in group 1 of monograph of International Agency for Research on Cancer. Transmission electron microscopy confirmed the generation of (nano)PANI (particle size 8-9 nm). Both membrane and (nano)PANI have been characterised by Fourier transmission infra-red spectroscopy, Scanning electron microscopy, X-ray diffraction and Atomic force microscopy. The swelling behaviour and mechanical properties of the composite membrane are also investigated. Incorporation of (nano) PANI in the polyimide matrix increases the polarity of the membrane, thereby increasing its selectivity towards 1-octene. The highest permeation flux and separation factor achieved are13.88 kg.m-2h-1 and 6.44 respectively at 333 K and 1 mm Hg downstream pressure.

Design of Monovalent Ion Selective Membranes for Reducing the Impacts of Multivalent Ions in Reverse Electrodialysis.

Reverse electrodialysis (RED) represents one of the most promising membrane-based technologies for clean and renewable energy production from mixing water solutions. However, the presence of multivalent ions in natural water drastically reduces system performance, in particular, the open-circuit voltage (OCV) and the output power. This effect is largely described by the “uphill transport” phenomenon, in which multivalent ions are transported against the concentration gradient. In this work, recent advances in the investigation of the impact of multivalent ions on power generation by RED are systematically reviewed along with possible strategies to overcome this challenge. In particular, the use of monovalent ion-selective membranes represents a promising alternative to reduce the negative impact of multivalent ions given the availability of low-cost materials and an easy route of membrane synthesis. A thorough assessment of the materials and methodologies used to prepare monovalent selective ion exchange membranes (both cation and anion exchange membranes) for applications in (reverse) electrodialysis is performed. Moreover, transport mechanisms under conditions of extreme salinity gradient are analyzed and compared for a better understanding of the design criteria. The ultimate goal of the present work is to propose a prospective research direction on the development of new membrane materials for effective implementation of RED under natural feed conditions.

Permeabilities and selectivities in anisotropic planar membranes for gas separations

The use of membrane technologies for separation processes is an alternative approach to reduce the environmental impact and energy demand of separations. The development of new membrane materials plays a central role to overcome the limitations of membranes in terms of selectivity, permeability, and stability. Most membrane materials in the past have been engineered to control the relative magnitude of the flux of the species diffusing through the membrane. However, mass flux is a vector and controlling its direction can open new opportunities to design separation processes. In this paper we characterize the separation capabilities of metamaterial-inspired anisotropic planar membranes by studying the development of spatially dependent permeabilities and selectivities as a consequence of manipulating the flux direction within the membrane. Specifically, we show how the performance of anisotropic planar membranes for separations can be characterized in terms of permeability, selectivity, and the collected permeate proportion. In contrast to isotropic membrane materials, we show how the selectivity under single stage operation can be increased beyond the selectivities of the constituent materials by reducing the permeate proportion that is collected. Our work provides new opportunities for the design of alternative separation processes that take advantage of flux directional control within membrane materials.

Nanocomposite membranes for osmotic processes: Incorporation of functionalized hydroxyapatite in porous substrate and in selective layer

Development of new membrane materials for osmotic processes is an important field for increasing the efficiency of the technology. In this work, hydroxyapatite particles (Hapf) functionalized by plasma treatment were added to a porous cellulose acetate substrate and to a selective polyamide layer of nanocomposite membranes to evaluate its performance in osmotic processes. Contact angle, scanning electron microscopy, FT-IR, zeta potential and atomic force microscopy were performed to characterize nanocomposite membranes. Hapf incorporation in the porous CA substrate improved the water flux in forward osmosis from 13.8 to 18.0 L·h−1·m−2, which was related to the augmented hydrophilicity and lower diffusion resistance of the substrate. The addition of particles in the selective layer allowed a further increase up to 22.6 L·h−1·m−2, without affecting the reverse salt flux. For reverse osmosis, water permeability increased from 0.83 to 1.41 L·h−1·m−2·bar−1, maintaining high rejection for NaCl and MgSO4, when particles were incorporated into the selective layer. Composite membranes with CA porous substrate and PA selective layer exhibited promising properties for forward osmosis, and the incorporation of novel functionalized Hapf in both layers allowed for a further adjustment of the membrane hydrophilicity and indicates an advance in membrane material technology.

Mass transport mechanisms within pervaporation membranes

Pervaporation is an energy-efficient membrane technology for separating liquid molecules of similar physical properties, which may compete or combine with distillation separation technology in a number of applications. With the rapid development of new membrane materials, the pervaporation performance was significantly improved. Fundamental understanding of the mass transport mechanisms is crucial for the rational design of membrane materials and efficient intensification of pervaporation process. Based on the interactions between permeate molecules and membranes, this review focuses on two categories of mass transport mechanisms within pervaporation membranes: physical mechanism (solution-diffusion mechanism, molecular sieving mechanism) and chemical mechanism (facilitated transport mechanism). Furthermore, the optimal integration and evolution of different mass transport mechanisms are briefly introduced. Material selection and relevant applications are highlighted under the guidance of mass transport mechanisms. Finally, the current challenges and future perspectives are tentatively identified.

50th Anniversary Perspective: Polymers and Mixed Matrix Membranes for Gas and Vapor Separation: A Review and Prospective Opportunities

Membrane gas separation is a mature and expanding technology. However, the availability of better membrane materials would promote faster growth. In this Perspective we analyze the state of the art of membrane materials, including polymers and hybrid materials, as well as the current issues and barriers, and finally, we outline future research directions in membrane science. Development of new membrane materials for large scale separations will rely on a multidisciplinary approach that embraces the broad fields of chemical and materials engineering, polymer science, and materials chemistry.

A review of oxygen removal from oxygen-bearing coal-mine methane.

In this article, a comparison will be made concerning the advantages and disadvantages of five kinds of coal mine methane (CMM) deoxygenation method, including pressure swing adsorption, combustion, membrane separation, non-metallic reduction, and cryogenic distillation. Pressure swing adsorption has a wide range of application and strong production capacity. To achieve this goal, adsorbent must have high selectivity, adsorption capacity, and adequate adsorption/desorption kinetics, remain stable after several adsorption/desorption cycles, and possess good thermal and mechanical stabilities. Catalytic combustion deoxygenation is a high-temperature exothermic redox chemical reaction, which releases large amounts of thermal energy. So, the stable and accurate control of the temperature is not easy. Meanwhile partial methane is lost. The key of catalytic combustion deoxygenation lies in the development of high-efficiency catalyst. Membrane separation has advantages of high separation efficiency and low energy consumption. However, there are many obstacles, including higher costs. Membrane materials have the requirements of both high permeability and high selectivity. The development of new membrane materials is a key for membrane separation. Cryogenic distillation has many excellence advantages, such as high purity production and high recovery. However, the energy consumption increases with decreasing CH4 concentrations in feed gas. Moreover, there are many types of operational security problems. And that several kinds of deoxygenation techniques mentioned above have an economic value just for oxygen-bearing CMM with methane content above 30%. Moreover, all the above methods are not applicable to deoxygenation of low concentration CMM. Non-metallic reduction method cannot only realize cyclic utilization of deoxidizer but also have no impurity gases generation. It also has a relatively low cost and low loss rate of methane, and the oxygen is removed thoroughly. In particular, the non-metallic reduction method has good development prospects for low concentration oxygen-bearing CMM. This article also points out the direction of future development of coal mine methane deoxygenation.

Enhanced ethylene separation and plasticization resistance in polymer membranes incorporating metal-organic framework nanocrystals.

The implementation of membrane-based separations in the petrochemical industry has the potential to reduce energy consumption significantly relative to conventional separation processes. Achieving this goal, however, requires the development of new membrane materials with greater selectivity, permeability and stability than available at present. Here, we report composite materials consisting of nanocrystals of metal-organic frameworks dispersed within a high-performance polyimide, which can exhibit enhanced selectivity for ethylene over ethane, greater ethylene permeability and improved membrane stability. Our results suggest that framework-polymer interactions reduce chain mobility of the polymer while simultaneously boosting membrane separation performance. The increased stability, or plasticization resistance, is expected to improve membrane utility under real process conditions for petrochemical separations and natural gas purification. Furthermore, this approach can be broadly applied to numerous polymers that encounter aggressive environments, potentially making gas separations possible that were previously inaccessible to membranes.

Novel nanofiltration membranes consisting of a sulfonated pentablock copolymer rejection layer for heavy metal removal.

Facing stringent regulations on wastewater discharge containing heavy metal ions, various industries are demanding more efficient and effective treatment methods. Among the methods available, nanofiltration (NF) is a feasible and promising option. However, the development of new membrane materials is constantly required for the advancement of this technology. This is a report of the first attempt to develop a composite NF membrane comprising a molecularly designed pentablock copolymer selective layer for the removal of heavy metal ions. The resultant NF membrane has a mean effective pore diameter of 0.50 nm, a molecular weight cutoff of 255 Da, and a reasonably high pure water permeability (A) of 2.4 LMH/bar. The newly developed NF membrane can effectively remove heavy metal cations such as Pb(2+), Cd(2+), Zn(2+), and Ni(2+) with a rejection of >98.0%. On the other hand, the membrane also shows reasonably high rejections toward anions such as HAsO4(2-) (99.9%) and HCrO4(-) (92.3%). This performance can be attributed to (1) the pentablock copolymer's unique ability to form a continuous water transport passageway with a defined pore size and (2) the incorporation of polyethylenimine as a gutter layer between the selective layer and the substrate. To the best of our knowledge, this is the first reported NF membrane comprising this pentablock copolymer as the selective material. The promising preliminary results achieved in this study provide a useful platform for the development of new NF membranes for heavy metal removal.

Separation of Bioactive Peptides by Membrane Processes: Technologies and Devices

Although many patents reported bioactive peptides with numerous demonstrated bioactivities and potential applications, there exist some limitations to the production of large quantities to satisfy the growing market demands. Indeed, considering that most functional peptides are present in complex matrices containing a large number of hydrolyzed protein fractions, their separation and purification are required. Some advances have been made in the use of conventional pressure-driven processes for the continuous production and separation of peptides, however, most of these patented technologies are not scalable and demonstrate a low selectivity when separating similar sized biomolecules. To improve the separation efficiency, the use of an external electric field during pressure-driven filtration was proposed and patented. However, whatever the claims, the pressure gradient brings about the accumulation of peptides at the nearby membrane surface and affects the membrane transport selectivity. To overcome these drawbacks, a recent patent proposed the simultaneous fractionation of acidic and basic peptides, using a conventional electrodialysis cell, in which some ion exchange membranes are replaced by ultrafiltration ones. The perspectives in the field of peptide separation will be the development of new membrane materials and new equipments such as microfluidic devices to improve selectivity and yield of production.

Membrane Separation of CO<sub>2 </sub>from Natural Gas: A State-of-the-Art Review on Material Development

Natural gas (NG) processing and membrane technology are two very important fields that are of great significance due to increasing demand for energy as well as separation of gas mixtures. While NG is projected to be the number one primary source of energy by 2050, membrane separation is a commercially successful competitor to other separation techniques for energy efficient gas separation processes [1]. Most of the NG produced in the world is coproduced with acid gases such as CO2which need to be removed to increase the caloric value of NG. A comprehensive review of research efforts in CO2separation from natural gas is required to capture details of the current scientific and technological progresses on the development of new membrane materials with better separation performance, and the improvement of properties of the existing ones. This paper presents the progress that has been achieved in eliminating the limitations that dominate the large scale application of membrane materials at the present time. Various polymers that have been developed to resist plasticization and the method employed to fabricate these polymers are highlighted. Also the range of plasticization pressures (together with corresponding selectivities and permeabilities at these pressures) that have so far been achieved by these fabrication methods is presented. It is believed that this review will serve as a good reference source especially for research in design and development of membrane materials with better resistance to CO2-induced plasticization.

Preparation and characterization of polyvinyl acetate/zeolite 4A mixed matrix membrane for gas separation

The demand and consumption of fossil fuels have increased in the past and continue to increase in future. The combustion of these fossil fuels produce various harmful gases i.e CO2, SO2, H2S etc. that pose potential threat to the environment. Currently the development of new membrane materials is the focus of research in membrane based gas separation. Pure PVAc and PVAc/4A mixed matrix membranes were prepared using dichloromethane as a solvent and the solution casing method. The resulting membranes were characterized by optical microscope, FESEM, DSC, TGA, XRD and single gas permeation. Optical microscope was used to find out the initial thickness of membranes that ranges from 70μm to 90μm. Zeolite 4A particles upto 35wt% were homogenously dispersed within the polymer without aggregation as shown by the FESEM results. The addition of 4A particles have improved the thermal stability of PVAc in the resulting MMMs as depicted by an increase in the glass transition temperature (Tg) and TGA results. In single gas permeation, the effects of zeolite 4A loading, operating temperature and pressure on the separation properties were investigated. The obtained results show that the addition of zeolite 4A up to 25wt% has increased the selectivity of gas pairs O2/N2, H2/N2 and CO2/N2 by 25%, 37% and 70% respectively with a corresponding decrease in their permeability. Temperature increase from 30°C to 50°C has a positive effect on permeabilities with a maximum of (1.19)×3.348×10−19kmolm/(m2sPa) (barrer) for O2, (17.55)×3.348×10−19kmolm/(m2sPa) (barrer) for H2 and (9.35)×3.348×10−19kmolm/(m2sPa) (barrer) for CO2 and a negative effect on their selectivity over N2. As the pressure is increased from (2)×100,000Pa (bars) to 8×100,000Pa (bars), permeability of H2 almost remains constant and slightly increases for O2. Permeability of N2 and CO2 is decreased and increased respectively leading to increased selectivity of CO2/N2 as well as H2/N2 and O2/N2. The obtained results are consistent with the reported literature data.

The Influence of Casting Machine Speed in Cellulose Acetate Membrane Preparation

Membranes are being increasingly used as a valuable separation tool in laboratory as well as in industrial processes. Continual development of new membrane materials is crucial to sustain and expand the growing interest in this technology and modern polymer chemistry is highly proficient in tailoring polymers with desired properties such as increased mechanical, thermal and chemical stability. Cellulose acetate (CA) is one of the membrane polymers that has been used for aqueous based separation and used as both reverses osmosis (RO) and ultrafiltration (UF) membranes. This paper presents investigation of influence of casting machine speed in membrane preparation. CA is used in this study. That was CA-398-30 with average acetyl content 39.8 wt %. Non solvent used is water and the solvent is 99.7 % organic Dimethyl Sulfoxide (DMSO). The homogenous CA/DMSO solutions were prepared by dissolving CA in DMSO solvent. The CA concentration were varied 13 and 16 % while casting solution speed were varied from 20 to 80 mm/sec with distance cutting machine were fixed at 14 cm. In addition, non solvent in coagulation bath also were varied by 100 % water and 10 % DMSO in water. The results of this experiment describe effect of casting machine speed to water permeability. The effect of CA concentration to water permeability shows the adversative result between 13 and 16 % CA in 100 non solvent water. The similar result also observed in 10 % DMSO in water.

Membrane Processes and Devices for Separation of Bioactive Peptides

In recent years, functional foods and nutraceuticals has attracted much attention, particularly for their impact on human health and prevention of certain diseases. Consequently, the production and properties of bioactive peptides has received an increasing scientific interest over the past few years. Considering that most functional peptides are present in complex matrices containing a large number of hydrolyzed protein fractions, their separation and purification are required. Conventional pressure-driven processes can be used for amino acids and peptides separation but are limited by their fouling problems and their low selectivity when separating similar sized biomolecules. To improve the separation efficiency, an external electric field was applied during pressure-driven filtration. However, the pressure gradient brings about the accumulation of peptides at the nearby membrane surface and affects the membrane transport selectivity. Processes combining an electrical field as a driving force to porous membranes have been developed for the separation of biopeptides to obtain better purified products. Compounds of higher molecular weights than the membrane cut-off can be separated. The first trials were carried-out to perform the separation of amino acids and peptides with a filtration module specially designed and using one ultrafiltration membrane. More recently, electrodialysis with ultrafiltration membranes has been developed to fractionate simultaneously acidic and basic peptides, using a conventional electrodialysis cell, in which some ion exchange membranes are replaced by ultrafiltration ones. The perspectives in this field will be the understanding of the interactions of peptides and membrane as well as the development of new membrane materials limitating or increasing these interactions to improve the selectivity and the yield of production of specific peptides. This review article also discusses recent patents related to bioactive peptides.

Physicochemical problems encountered in the development of oxygen-conducting oxide materials for new devices for chemical energy conversion

The data on the properties of ion- and mixed-conducting oxides promising for the development of new membrane materials for processing natural gases and solid-oxide fuel cells with low working temperatures (<800 K) are presented. Advantages of using perovskite-type oxides based on hetero-substituted lanthanum gallate for the development of materials for oxygen-selective electrolytes and electrodes are substantiated. The most promising methods for the production of low-defect thin-film structures providing the efficient conversion of the hydrocarbon fuel energy are considered.

Micro- and nano-characterization of membrane materials

The global warming has led to enormous challenges worldwide for a large variety of communities, particularly these associated to water and water treatment industry. Due to increasing scarcity of water resources, the development of new membrane materials and water treatment processes will play an important role in tackling this emerging problem. In this paper, the recent development in characterization of in particular, geometrical parameters of micro- and nano-membrane materials will be reviewed. Membranes with micro- and nano-pores have widely been used for ultrafiltration and nanofiltration. The structure of the pores and the surface of the pores/membranes may be optimized to achieve much improved flow rate in these micro-/nano-channels. Therefore, accurate characterization of porous structures will contribute significantly to the prediction of membrane performance. It will not only provide an insight into the new characterization methods but also the development of novel materials.

Microwave power for smart material actuators

The concept of microwave-driven smart material actuators was envisioned anddeveloped as the best option to alleviate the complexity and weight associatedwith a hard-wire-networked power and control system for smart actuator arrays.The patch rectenna array was initially designed for high current output, but hasundergone further development for high voltage output devices used in shape controlapplications. Test results show that more than 200 V of output were obtained from a6 × 6 array at a far-field exposure (1.8 m away) with an X-band input power of 18 W. The6 × 6 array patch rectenna was designed to theoretically generate voltages up to 540 V,but practically it has generated voltages in the range between 200 and 300 V.Testing was also performed with a thin layer composite unimorph ferroelectricdriver and sensor and electro-active paper as smart actuators attached to the6 × 6 array. Flexible dipole rectenna arrays built on thin-film-based flexible membranes are mostapplicable for NASA’s various missions, such as microwave-driven shape controls foraircraft morphing and large, ultra-lightweight space structures. An array of dipolerectennas was designed for high voltage output by densely populating Schottky barrierdiodes to drive piezoelectric or electrostrictive actuators. The dipole rectenna array willeventually be integrated with a power allocation and distribution logic circuit andmicrobatteries for storage of excessive power. The roadmap for the development of wirelesspower drivers based on the rectenna array for shape control requires the development ofnew membrane materials with proper dielectric constants that are suitable for dipolerectenna arrays.