Dual-layer Membranes Research Articles

Catalytic membrane with dual-layer structure for ultrafast degradation of emerging contaminants in surface water treatment

The catalytic membrane-based oxidation-filtration process integrates physical separation and chemical oxidation, offering a highly efficient water purification strategy. However, the oxidation-filtration process is limited in practical applications due to the short residence time of milliseconds within the catalytic layer and the interference of coexisting organic pollutants in real water. Herein, a dual-layer membrane containing a top selective layer and a bottom catalytic layer was fabricated using an in situ co-casting method with a double-blade knife. Experimental results demonstrated that the selective layer rejected macromolecular organic pollutants, thereby alleviating their interference with bisphenol A (BPA) degradation. Concurrently, the catalytic layer activated peracetic acid oxidant and achieved a high BPA degradation exceeding 90 % in milliseconds with reactive oxygen species (especially •OH). The finite-element analysis confirmed a high-concentration reaction field occupying the pore cavity of the catalytic layer, enhancing collision probability between reactive oxygen species and BPA, i.e., the nano-confinement effect. Additionally, the dual-layer membrane achieved a long-term stable performance for emerging contaminant degradation in surface water treatment. This work underscores a novel catalytic membrane structure design for high-performance oxidation-filtration processes and elucidates its mechanisms underlying ultrafast degradation.

A fully nanofiber-based ultrathin electronic patch for self-powered and multifunctional on-skin applications

On-skin electronics that simultaneously ensure biocompatibility and stable electrical operation on soft tissue is still challenging. This study introduces a dual-layered and natural material based nanofiber platform designed for multifunctional on-skin operation (from energy harvesting to transdermal drug delivery). The ultrathin electronic patch consists of polyaniline (PANI)-coated cellulose nanofibers and silk fibroin nanofibers. The top PANI/cellulose nanofiber layer, exhibiting the resistivity of 0.315 Ω·m and over 90 % light absorbance in full visible range, functions as a flexible electrode. The silk nanofiber layer offers the skin-compatibility and strong adhesion to biological tissues, along with the capability of drug-loading. The nanofiber mesh structure withstands mechanical deformation, including compression, stretching, and bending, while its porous nature enhances breathability and hygiene. The fully nanofiber-based electronic patch platform is flexible, adheres well to the skin, and conforms to curved surfaces. By integrating the conductive properties of PANI with the biocompatibility of silk fibroin, this dual-layered membrane enhances the efficacy of transdermal drug delivery while offering multifunctional capabilities such as energy harvesting in a triboelectric nanogenerator (TENG), programmable drug delivery, and thermal therapy. This innovative approach paves the way for advanced biomedical applications by combining multiple functionalities in a single platform.

Dual-layer nanofibrous PCL/gelatin membrane as a sealant barrier to prevent postoperative pancreatic leakage

Post-operative pancreatic leakage is a severe surgical complication that can cause internal bleeding, infections, multiple organ damage, and even death. To prevent pancreatic leakage and enhance the protection of the suture lining and tissue regeneration, a dual-layer nanofibrous membrane composed of synthetic polymer polycaprolactone (PCL) and biopolymer gelatin was developed. The fabrication of this dual-layer (PGI-PGO) membrane was achieved through the electrospinning technique, with the inner layer (PGI) containing 2% PCL (w/v) and 10% gelatin (w/v), and the outer layer (PGO) containing 10% PCL (w/v) and 10% gelatin (w/v) in mixing ratios of 2:1 and 1:1, respectively. Experimental results indicated that a higher gelatin content reduced fiber diameter enhanced the hydrophilicity of the PGI layer compared to the PGO layer, improved the membrane’s biodegradability, and increased its adhesive properties. In vitro biocompatibility assessments with L929 fibroblast cells showed enhanced cell proliferation in the PGI-PGO membrane. In vivo studies confirmed that the PGI-PGO membrane effectively protected the suture line without any instances of leakage and promoted wound healing within four weeks post-surgery. In conclusion, the nanofibrous PGI-PGO membrane demonstrates a promising therapeutic potential to prevent postoperative pancreatic leakage.

A Comprehensive Review of Hollow-Fiber Membrane Fabrication Methods across Biomedical, Biotechnological, and Environmental Domains.

This work presents methods of obtaining polymeric hollow-fiber membranes produced via the dry-wet phase inversion method that were published in renowned specialized membrane publications in the years 2010-2020. Obtaining hollow-fiber membranes, unlike flat membranes, requires the use of a special installation for their production, the most important component of which is the hollow fiber forming spinneret. This method is most often used in obtaining membranes made of polysulfone, polyethersulfone, polyurethane, cellulose acetate, and its derivatives. Many factors affect the properties of the membranes obtained. By changing the parameters of the spinning process, we change the thickness of the membranes' walls and the diameter of the hollow fibers, which causes changes in the membranes' structure and, as a consequence, changes in their transport/separation parameters. The type of bore fluid affects the porosity of the inner epidermal layer or causes its atrophy. Porogenic compounds such as polyvinylpyrrolidones and polyethylene glycols and other substances that additionally increase the membrane porosity are often added to the polymer solution. Another example is a blend of two- or multi-component membranes and dual-layer membranes that are obtained using a three-nozzle spinneret. In dual-layer membranes, one layer is the membrane scaffolding, and the other is the separation layer. Also, the temperature during the process, the humidity, and the composition of the solution in the coagulating bath have impact on the parameters of the membranes obtained.

Hyperbranched polymeric membranes for industrial water purification

This work aims at the preparation and characterization of dual-layer (DL) nano-fibrous mat (NFM) of hydrophobic and mechanical stable polyacrylonitrile (PAN) nano-fibers (NFs), as a supporter, and polyamide 6 (PA)/chitosan (Ch) NFs as a top hydrophilic coating layer.PAN and PA fibers, as residual wastes from textile processes, were collected and dissolved in their proper solvents. PAN was electro-spuned under certain conditions of electro-spinning (voltage, flow rate, and distance between spinneret and collector) to obtain PAN-NFM. Different ratios of PA/Ch composite were prepared and then electro-spun above the PAN-NFM that was previously prepared to obtain hydrophobic/hydrophilic functional dual-layer nano-fibrous membrane (DLNFM). The efficiency of the prepared DLNFM for capturing dye residues and heavy metals from wastewater was investigated.The viscosities of the prepared composite solutions were measured. The prepared dual-layer nano-fiber membranes (DLNFMs) were chemically and physically characterized by Fourier transform infrared spectroscopy, scanning electron microscope, X-ray diffraction, and thermogravimetric analyzer. The potential of the prepared mats for the adsorption of some heavy metal ions, i.e., Cu+2, Cr+3, and Pb+2 cations in addition to dyes from wastewater was evaluated. The effect of using different concentrations of PA/Ch composite as well as the thickness of the obtained DLNFM on the filtration efficiency was studied.The results of this study show the success of functional DLNFM in dye and heavy metal removal. The maximum removal efficiency of acid dyes was reached to 73.4 % and of reactive dye was approximately 61 % for PAN/PA-1.25%Ch DLNFM after 3 days at room temperature. The removal efficiency percent of heavy metal ions reached to 54 % by DLNFM. Additionally, the results showed that 0.08 mm is the ideal thickness for maximum absorption capacity. This value is correlated with the membrane's highest Ch percentage, which is (PAN/PA-1.25%Ch). Furthermore, the results demonstrate that the presence of the Ch polymer strengthened the produced bi-layered membrane to achieve the highest thermal stability when compared to the other nano-fibrous membranes (NFMs), with the breakdown temperature of the Ch functionalized dual-layer membranes (DLMs) reaching approximately 617 °C and a maximum weight loss of 60 %.

Mixed Matrix Pt-Carbon Nanofiber Polyethersulfone Catalytic Membranes for Glucose Dehydrogenation.

The advancement of technologies for producing chemicals and materials from non-fossil resources is of critical importance. An illustrative example is the dehydrogenation of glucose, to yield gluconic acid, a specialty chemical. In this study, we propose an innovative production route for gluconic acid while generating H2 as a co-product. Our concept involves a dual-function membrane, serving both as a catalyst for glucose dehydrogenation into gluconic acid and as a means to efficiently remove the produced H2 from the reaction mixture. To achieve this two membranes were developed, one catalytically active and one dense aimed at H2 removal. The catalytic membrane showed significant activity, yielding 16 % gluconic acid (t=120 min) with a catalyst selectivity of 93 % and stable performance over five consecutive cycles. Incorporating the H2 separating membrane showed the significance of H2 removal in driving the reaction forward. Its inclusion led to a twofold increase in gluconic acid yield, aligning with Le Chatelier's principles. As a future prospect the two layers can be combined into a dual-layer membrane which opens the way for a new production route to simultaneously produce gluconic acid and H2, using high-throughput reactors such as hollow-fiber systems.

Novel dual-layer ZIF-71/PH-PSF electrospun nanofiber for robust membrane distillation

Membrane distillation (MD) is a promising technology for the treatment of hypersaline dyeing wastewater. However, commercial membranes still have limitations such as low permeate flux, membrane fouling, and membrane wetting issue in MD process. Herein, a dual-layer MD membrane was fabricated with a polysulfone (PSF) bottom layer and a poly(vinylidene fluoride-co-hexafluoropropylene) (PH) hydrophobic surface layer incorporated with ZIF-71 nanoparticles. The addition of ZIF-71 was optimized based on the results of surface morphology, contact angle, and MD performance. The incorporation of ZIF-71 nanoparticles into PH nanofiber membranes, along with their dual-layer structure, has led to notable improvements in both permeate flux and rejection performance. The fouling resistance of membrane was further evaluated with model dyeing wastewater as feed solution, which contained four types of dyes and heavy metal antimony. The MD performance of the optimized membranes was also measured with real dyeing wastewater as feed solution. The dual-layer membrane decorated with ZIF-71 nanoparticles significantly outperformed the pristine membrane in treating real dyeing wastewater, exhibiting potential for practical applications. Finally, the underlying mechanism on the improved permeate flux and rejection was elucidated systematically.

A dual-layer membrane with antibacterial property for efficient purification of wastewater containing Congo red and oil-in-water emulsion

It's urgent to prepare membranes which can treat wastewater containing complex contaminants. Herein we report a dual-layer membrane containing a topside Co-MOF/Co(OH)2 layer and a bottom PANI layer on the polyamide microfiltration substrate. The membrane could realize a rejection of over 99.6 % for diesel-in-water emulsion with the permeance around 50–100 L m−2 h−1 bar−1 within three one-hour separation rounds. Meanwhile, the membrane could also separate wastewater containing Congo red with the permeance of 300–500 L m−2 h−1 bar−1 and the rejection above 93 %. For complex wastewater containing diesel-in-water emulsion and CR, the membrane displayed satisfactory separation ability. Furthermore, the membrane displayed excellent antibacterial activity against both gram-negative E. coli and gram-positive S. aureus, which would help it to avoid fouling by bacteria during the separation. Our work effectively constructs a composite membrane, which provides an effective strategy for the treatment of water containing oil/water emulsions and dyes.

Sulfonic acid (-HSO3) functionalization effect on graphene oxide membrane by (3 mercaptopropyl) trimethoxysilane and their applications in hydrogen membrane fuel cells

Conventional proton exchange membrane fuel cells (PEMFCs) use a perfluorinated ionomer membrane, e.g., Nafion®, which is expensive and subject to a rigorous synthesis process. Graphene oxide membrane (GOM) is acknowledged as a promising alternative electrolyte due to its hydrophilic nature and attractive proton conductivity in wet conditions. However, GOM loses its negative surface functional groups by hydrogen gas at the anode during operation in PEMFCs, resulting in increased electronic conductivity. In addition, two-dimensional graphene oxide (GO) nanosheets exhibited a larger anisotropy difference in proton conductivity compared to Nafion®. In this study, (3-mercaptopropyl)trimethoxysilane (MPTS, HS(CH2)3Si(OCH3)3) was reacted with the surface of GO nanosheet (M-GOM) by vigorous stirring, where unreacted MPTS was partially removed by a rinsing cycle except the M-GOM powder. Reactive MPTS has two essential reactions which were carried out by forming a hydrolysis reaction (Si-OCH3 to Si-OH) and a condensation reaction (Si-OH to Si-O-Si). The thiol groups of MPTS were oxidized to sulfonic acid groups (-HSO3) to provide high proton conducting stations with GO functional groups (M-GOM/oxid) and compared with non-oxidized thiol groups in a GO matrix (M-GOM/unoxid). The superior –HSO3 effect on M-GOM have reported for proton conductivity, physicochemical properties, ion exchange capacity, thermal stability, gas permeability and fuel cell performance. Furthermore, a hydrogen-permeable metal layer was deposited by a DC magnetron sputter to increase mechanical strength and reduce fuel crossover. A dual-layer membrane composed of M-GOM/unoxid or M-GOM/oxid and Pd thin film was analyzed as an electrolyte for a hydrogen membrane fuel cell (HMFC), which simultaneously performs two roles, an anode catalyst and an electrolyte.

Fabrication and characterization of hydrophobic/hydrophilic dual-layer polyphenyl sulfone Janus membrane for application in direct contact membrane distillation

In this study, single-layer (SL) and dual-layer (DL) polyphenyl sulfone (PPSU) flat sheet nanocomposite Janus membranes were fabricated via a combination of VIPS and NIPS techniques for direct contact membrane distillation (DCMD) for the first time. Hydrophobic silica nanoparticles (SiNP-B) were incorporated into the SL membranes and the top layer of the DL membranes, while hydrophilic silica nanoparticles (SiNP-L) were added into the down layer of the DL membranes. The effect of the SiNP-B concentration (1–5 wt%) and the top layer thickness (50 and 100 μm) on the morphology, mean pore size (MPS), thickness, porosity, surface roughness, water contact angle (WCA), liquid entry pressure, mechanical strength, and thermal conductivity were investigated. All of the membranes showed a finger-like structure surrounded by a sponge-like structure. The membranes were examined in the DCMD of a 35,000 ppm saline solution at different feed temperatures (50–70 °C) and flow rates (250–1000 mL/min). The DL membranes possessed higher fluxes than the SL membranes through increasing MPS and WCA. The DL membrane with a SiNP-B concentration of 2 wt% and a hydrophobic thickness of 50 μm (DL- 2,50) achieved the highest flux (42.68 ± 0.35 kg/m2h) and salt rejection (94.90 %) during 5 h. This membrane has an MPS of 0.22 ± 0.03 μm, a thickness of 201 ± 4 μm, and a porosity of 76 ± 2 %. It could be concluded the proper pore size distribution is the most important factor in achieving a successful DCMD operation.

Enhancing Hydrophobic/Hydrophilic Dual-Layer Membranes for Membrane Distillation: The Influence of Polytetrafluoroethylene (PTFE) Particle Size and Concentration

This study assesses the effects of different polytetrafluoroethylene (PTFE) particle sizes and concentrations on the performance of dual-layer membranes in direct contact membrane distillation (DCMD). Specifically, particle sizes of 0.5 μm, 1 μm, and 6 μm were systematically evaluated at concentrations of 0 wt%, 2 wt%, 4 wt%, and 6 wt%. Comprehensive analyses, including scanning electron microscopy (SEM), liquid entry pressure (LEP), contact angle, thermogravimetric analysis (TGA), mercury intrusion porosimetry (MIP), atomic force microscopy (AFM), permeate flux, nitrogen gas permeation, and salt rejection, were employed to characterize the membranes. Under conditions of a feed temperature of 70 °C and a salt concentration of 8000 ppm for a 24 h duration, the results clearly indicated that a 0.5 μm PTFE particle size combined with a 6 wt% concentration exhibited the highest performance. This configuration achieved a permeate flux of 11 kg·m2/h and a salt rejection rate of 99.8%. The outcomes of this research have significant implications for the optimization of membranes used in DCMD applications, with potential benefits for sustainable water treatment and energy conservation.

Triple-layer nanofiber membrane with improved energy efficiency for treatment of hypersaline solution via membrane distillation

A new triple-layer, electrospun nanofiber membrane was fabricated in sequential electrospinning steps for enhancing the thermal efficiency of the membrane for desalination of high-salinity solution in a membrane distillation process. The membrane structure is designed to form a Janus structure comprised of two hydrophobic layers made of polyvinylidene fluoride and polystyrene at the top and middle, respectively, and one hydrophilic layer made of polyacrylonitrile at the bottom layer (support). The low thermal conductivity of the polystyrene layer and the Janus structure of the membrane could considerably enhance the flux and thermal performance of the membrane for desalination of hypersaline solution. The experimental results demonstrated that the designed membrane achieved high permeate flux and high energy efficiency compared with single and dual-layer membranes when used for treatment of high salinity solution. The results further showed that increasing feedwater salinity dropped the permeate flux of the single-layer membrane by over 50 % and reached 10 L/m2h, while for the triple-layer membrane, it just dropped 20 % for the feed salinity of 200 g/l. Moreover, the triple-layer membrane showed 20 % higher energy efficiency at the same operation conditions. Furthermore, a simulation model was developed and validated via the experimental results to understand the effect of various parameters.

Thin-Film Composite Matrimid-Based Hollow Fiber Membranes for Oxygen/Nitrogen Separation by Gas Permeation.

In recent years, the need to reduce energy consumption worldwide to move towards sustainable development has led many of the conventional technologies used in the industry to evolve or to be replaced by new alternatives. Oxygen is a compound with diverse industrial and medical applications. For this reason, obtaining it from air is one of the most interesting separations, traditionally performed by cryogenic distillation and pressure swing adsorption, two techniques which are very energetically expensive. In this sense, the implementation of membranes in a hollow fiber configuration is presented as a much more efficient alternative to carry out this separation. The aim of this work is to develop cost-effective multilayer hollow fiber composite membranes made of Matrimid and polydimethylsiloxane (PDMS) for the separation of oxygen and nitrogen from air. PDMS is used as a cover layer but can also enhance the performance of the membrane. In order to compare these two materials, three different configurations are studied. First, integral asymmetric Matrimid hollow fiber membranes were produced using the spinning method. Secondly, by using dip-coating method, a PDMS dense selective layer was deposited on a self-made polyvinylidene fluoride (PVDF) hollow fiber support. Finally, the performance of a dual-layer hollow fiber membrane of Matrimid and PDMS was studied. Membrane morphology was characterized by SEM and separation performance of the membranes was evaluated by mixed-gas permeation experiments. The novelty presented in this work is the manufacture of hollow fiber membranes and the way Matrimid is treated. This makes it possible to develop much thinner dense layers than in the case of flat-sheet membranes, which leads to higher permeance values. This is a key factor when implementing this technology on an industrial scale. Membranes prepared in this work were compared to the current state of the art, reporting quite good performance for the dual-layer membrane, reaching O2 permeance of 30.8 GPU and O2/N2 selectivity of 4.7, with a thickness of about 5-10 μm (counting both selective layers). In addition, the effect of operating temperature on the membrane permeances has been studied experimentally; we analyze its influence on the selectivity of the separation process.

Fabrication of CO2-tolerant SrFe0.8Nb0.2O3-δ/SrCo0.9Nb0.1O3-δ dual-layer 7-channel hollow fiber membrane by co-spinning and one-step thermal process

CO2-tolerant membranes are crucial for oxyfuel combustion systems utilizing oxygen permeable membranes. A newly constructed dual-layer 7-channel hollow fiber membrane consisting of SrFe0.8Nb0.2O3-δ (SFN) porous outer layer and SrCo0.9Nb0.1O3-δ (SCN) hollow fiber inner layer has been successfully fabricated by co-spinning and one-step thermal process (OSTP) approach in this work. The outer layer can have different porous structures depending on the graphite content of the spinning solution. In the OSTP approach, the in-situ reactive sintering of the membrane materials results in the two layers being well adhered and mechanically robust. At 900 °C under 80% CO2-containing in sweeping gas, the oxygen flux of SFN/SCN dual-layer hollow fiber membrane with the porous layer of 91.8 μm was 1.98 mL min−1 cm−2, about 7.1 times as much as the SCN hollow fiber membrane (0.28 mL min−1 cm−2) in the same situations. The porous SFN outer layer was demonstrated to prevent membrane performance degradation effectively. Furthermore, the SFN/SCN dual-layer membrane operated in a 20% CO2-containing atmosphere for at least 200 h, maintaining an oxygen flux of 3.20 mL min−1 cm−2 without degradation. As a result of these findings, the SFN/SCN dual-layer 7-channel hollow fiber membrane has significant application potential in CO2 capture for oxyfuel combustion.

A Comparison between Various Polymeric Membranes for Oily Wastewater Treatment via Membrane Distillation Process.

Oily wastewater (OW) is detrimental towards the environment and human health. The complex composition of OW needs an advanced treatment, such as membrane technology. Membrane distillation (MD) gives the highest rejection percentage of pollutants in wastewater, as the membrane only allows the vapor to pass its microporous membrane. However, the commercial membranes on the market are less efficient in treating OW, as they are prone to fouling. Thus, the best membrane must be identified to treat OW effectively. This study tested and compared the separation performance of different membranes, comparing the pressure-driven performance between the membrane filtration and MD. In this study, several ultrafiltration (UF) and nanofiltration (NF) membranes (NFS, NFX, XT, MT, GC and FILMTEC) were tested for their performance in treating OW (100 ppm). The XT and MT membranes (UF membrane) with contact angles of 70.4 ± 0.2° and 69.6 ± 0.26°, respectively, showed the best performance with high flux and oil removal rate. The two membranes were then tested for long-term performance for two hours with 5000 ppm oil concentration using membrane pressure-filtration and MD. The XT membrane displayed a better oil removal percentage of >99%. MD demonstrated a better removal percentage; the flux reduction was high, with average flux reduction of 82% compared to the membrane pressure-filtration method, which experienced a lower flux reduction of 25%. The hydrophilic MT and XT membranes have the tendency to overcome fouling in both methods. However, for the MD method, wetting occurred due to the feed penetrating the membrane pores, causing flux reduction. Therefore, it is important to identify the performance and characteristics of the prepared membrane, including the best membrane treatment method. To ensure that the MD membrane has good anti-fouling and anti-wetting properties, a simple and reliable membrane surface modification technique is required to be explored. The modified dual layer membrane with hydrophobic/hydrophilic properties is expected to produce effective separation in MD for future study.

Enhancing the Total Salt Adsorption Capacity and Monovalent Ion Selectivity in Capacitive Deionization Using a Dual-Layer Membrane Coating Electrode

Capacitive deionization (CDI) is highly attractive for seawater desalination, while the trade-off between total salt adsorption capacity (SAC) and monovalent ion selectivity is a big challenge for current electrodes, especially facing solution containing organics. Herein, a simple approach was used to prepare a novel dual-layer membrane coating electrode (D-MCE) by depositing ion exchange polymers onto activated carbon fiber (ACF) to overcome this issue. Performances of the ACF, single-layer MCE, anion exchange membrane ACF, and D-MCE were investigated. Compared to ACF, the single-layer MCE showed an increased total SAC from 435.7 to 593.0 μmol/g with a reduced Cl–/SO42– selectivity from 0.9 to 0.4. The introduction of the membrane increased total SAC to 524.3 μmol/g and decreased Cl–/SO42– selectivity to 0.7. The D-MCE exhibited an improved total SAC to 679.5 μmol/g by inhibiting the co-ion repulsion and Faradaic reaction. Meanwhile, the D-MCE enabled fast Cl– diffusion and presented a high selectivity (3.8). After 50 cycles, the D-MCE exhibited an almost unchanged total SAC and selectivity even in the presence of organics. The narrowed pores and negative outermost layer endowed the D-MCE with an outstanding anti-fouling behavior, which well explained its stable performance. These findings confirmed the high potential of the D-MCE in addressing the trade-off and provided valuable insights into the design of the CDI electrode for desalination.

Investigation of the performance of dual-layered omniphobic electrospun nanofibrous membranes for direct contact membrane distillation

Direct contact membrane distillation (DCMD) is a viable one-stop solution for sustainable seawater desalination and wastewater recovery. In this study, robust dual-layered omniphobic electrospun nanofibrous membranes (ENFMs) were fabricated with a re-entrant architecture and low surface free energy. This was achieved by incorporating hydrophobic mesocellular silica foam (MCF-5) into the top layer, followed by the surface functionalisation with 1 H, 1 H, 2 H, 2 H Perfluorodecyltriethoxysilane to improve the membrane anti-wetting and anti-fouling resistance. The dual-layered ENFMs exhibited a high porosity and a water contact angle ≃ of 143˚ and displayed an excellent vapour flux of ∼ 8.5 Lm−2h−1 and NaCl rejection > 99.99% when tested with synthetic seawater. The long-term desalination of natural seawater revealed that the normalised permeate flux was > 0.98 (NaCl rejection > 99.97%), and a simple water wash could recover the loss of membrane hydrophobicity and performance caused by the membrane scaling. The fabricated ENFMs displayed excellent permeate quality (< 1 ppm organic content and < 30 µS/cm) when evaluated with synthetic wastewater containing pharmaceutical compounds (acetaminophen, diclofenac sodium, ibuprofen and amoxicillin). The dual-layered membranes demonstrated outstanding anti-wetting ability when challenged with increasing concentration of cationic surfactant cetyltrimethylammonium bromide (CTAB 1.5 mM) in saline oily wastewater. The preliminary investigations revealed that these ENFMs hold great potential to be further investigated for enhanced water recovery.

Adsorptive Membrane for Boron Removal: Challenges and Future Prospects.

The complexity of removing boron compounds from aqueous systems has received serious attention among researchers and inventors in the water treating industry. This is due to the higher level of boron in the aquatic ecosystem, which is caused by the geochemical background and anthropogenic factors. The gradual increase in the distribution of boron for years can become extremely toxic to humans, terrestrial organisms and aquatic organisms. Numerous methods of removing boron that have been executed so far can be classified under batch adsorption, membrane-based processes and hybrid techniques. Conventional water treatments such as coagulation, sedimentation and filtration do not significantly remove boron, and special methods would have to be installed in order to remove boron from water resources. The blockage of membrane pores by pollutants in the available membrane technologies not only decreases their performance but can make the membranes prone to fouling. Therefore, the surface-modifying flexibility in adsorptive membranes can serve as an advantage to remove boron from water resources efficiently. These membranes are attractive because of the dual advantage of adsorption/filtration mechanisms. Hence, this review is devoted to discussing the capabilities of an adsorptive membrane in removing boron. This study will mainly highlight the issues of commercially available adsorptive membranes and the drawbacks of adsorbents incorporated in single-layered adsorptive membranes. The idea of layering adsorbents to form a highly adsorptive dual-layered membrane for boron removal will be proposed. The future prospects of boron removal in terms of the progress and utilization of adsorptive membranes along with recommendations for improving the techniques will also be discussed further.

Tailored alginate/PCL-gelatin-β-TCP membrane for guided bone regeneration

Membranes prepared for guided bone regeneration (GBR) signify valued resources, inhibiting fibrosis and assisting bone regenration. However, existing membranes lack bone regenerative capacity or adequate degradation profile. An alginate-casted polycaprolactone-gelatin-β-tricalcium phosphate dual membrane was fabricated by electrospinning and casting processes to enhance new bone formation under a GBR process. Porous membranes were synthesized with suitable hydrophilicity, swelling, and degradation behavior to confirm the compatibility of the product in the body. Furthermore, osteoblast-type cell toxicity and cell adhesion results showed that the electrospun membrane offered compatible environment to cells while the alginate sheet was found capable enough to supress the cellular attachment, but was a non-toxic material. Post-implantation, the in-vivo outcomes of the dual-layered membrane, showed appreciable bone formation. Significantly, osteoid islands had fused in the membrane group by eight weeks. The infiltration of fibrous tissues was blocked by the alginate membrane, and the ingrowth of new bone was enhanced. Immunocytochemical analysis indicated that the dual membrane could direct more proteins which control mineralization and convene osteoconductive properties of tissue-engineered bone grafts.

Hierarchically porous interlayer for highly permeable and fouling-resistant ceramic membranes in water treatment

Ceramic membranes are being increasingly adopted in water and wastewater treatment owing to their performance and long-term benefits. In addition to the attempts to reduce the fabrication cost, rationalizing the microstructure of ceramic membranes also draws increasing attention. In this work, titania (TiO2) nanoparticle suspensions with and without polystyrene beads (PS beads) were successively coated on the macroporous Al2O3 support. Followed by co-sintering the two layers at 850 °C, the PS beads in the interlayer were removed, and a dual-layer membrane structure with the hierarchically porous interlayer being covered by a well-integrated top filtration layer was successfully produced. The open porosity and thickness of the interlayer and top layer was optimized by the content of PS beads and TiO2 particles, respectively. The interlayer with a thickness of ∼ 19 μm was rationalized with 40 vol% of PS to achieve a balance between the high open porosity (∼58%) and well structural stability. Significantly, the ceramic membranes with the hierarchically porous interlayer showed largely increased water flux (1000 ∼ 2000 LMH) yet insignificant reduction in removal efficiency (up to 86%) to 90 nm PS beads (2 ppm) compared to the control (<500 LMH and ∼ 89%). The membrane fouling mechanism in sodium alginate solution (50 mg/L) was revealed to be intermediate pore blocking in the entire filtration process, while that of the conventional ceramic membrane rapidly developed to the cake layer. This suggests that the ceramic membranes with a hierarchically porous interlayer are of high efficiency in water treatment due to the enhanced permeate flux and retarded membrane fouling process.