Permeation Properties Of Membranes Research Articles

How to isolate channel-forming membrane proteins using the E. coli expression system.

The recombinant expression, isolation and characterization of pore-forming proteins is one of the most commonly used strategies for understanding the permeability properties of the biological membrane into which they are embedded. This protocol describes how to quantify the expression of your protein of interest and use this information to optimize its production using the Escherichia coli strain BL21Gold(de3)ΔABCF. It explains with a step-by-step approach how to separate the bacterial compartments according to their solubility and how to extract your protein of interest in its native conformation using detergent solutions. Finally, it describes how to improve its purity via ion-exchange chromatography and insert the purified porins into outer membrane vesicles, from which they can be copurified. The protocol is simpler and less empirical than those described for most channel-forming membrane proteins and also provides a solid foundation for the isolation of soluble proteins. Several parameters can be optimized on a case-by-case basis: expression time and temperature, concentration of the inducer, nature and concentration of the detergent, incubation time and temperature, pH and ionic strength of the purification buffers. This protocol is effective with prokaryotic channel-forming membrane proteins and can be employed for the production of pore-forming proteins from chloroplasts, mitochondria or eukaryotes in general. With minor optimization, this protocol can be adapted for the isolation of receptors, carrier, pumps or any other membrane-active proteins.

Formulation and Ex Vivo Evaluation of Membrane Permeation Properties of a Mixed Acetaminophen Gel for Rectal Administration

The purpose of this work was to evaluate the permeation of a mixed native starch-based gel of Ipomoea batatas (Convolvulaceae), using acetaminophen as a tracer through a rat rectal membrane (ex vivo method). The formulated gel was composed of a 10 g solution of poloxamer 407 at 20% and 2.5 g of glycerolized potato starch. The gel obtained was a smooth, homogeneous mixed gel with no foam, air bubbles or lumps, there was no characteristic odor, and the gel was whitish in color. This gel was characterized at the physicochemical and rheological level by means of the viscosimeter KINEXUS, pH- meter EUTECH and the study of the permeation was carried out by means of the Ussing chamber of horizontal type (the dual chamber). The formulated mixed gel is thermogelling, rheofluidifying and viscoelastic with a gelling temperature of 23.83; the permeation study gave a relatively low permeation percentage of 0.16% but which can be improved. The different viscoelastic, rheofluidizing and thermogelling characteristics contained in this mixed gel as well as the pH did not influence the permeation of the active ingredient (AP) through the rat rectal mucosa.

Properties of ceramic membranes obtained from kaolinitic clay mixed with palm and mango wastes from Cameroon: Application to wastewater treatment from breweries

AbstractThis work focuses on the development of new ceramic membranes based on mixtures of low‐cost and locally available raw materials such as kaolinitic clay and additives such as palm kernel shells and mango seed shells, which are used as pore‐forming agents to increase pore size, and on their efficiencies in rejecting organic and inorganic pollutants from brewery wastewater. The physical and chemical properties of raw materials were characterized via X‐ray diffraction, scanning electron microscopy, differential thermal analysis/thermogravimetry, energy dispersive X‐ray, and Fourier transform infrared spectrophotometry. Sintering was performed at 1100°C, and the permeability and mechanical properties of circular membranes were determined. The membrane filtration operation was used to assess the physicochemical parameters of the wastewater. The membrane composed of 85% kaolinite and 15% mango seed shells showed the best performance. The effective treatment of the breweries wastewater reduced the level of contamination by organic pollutants in the discharge water, with a reduction in concentration from 700 to 14 mg O2 L‒1 of chemical oxygen demand and 250 to 06 mg O2 L‒1 of biological oxygen demand for 5 days, representing elimination rates of 98% and 97.6%, respectively. The treated water is alkaline, with a reduction in pH from 10.79 to 7.77. Suspended matter, turbidity, and electrical conductivity had removal rates of 88%, 90.6%, and 99.8%, respectively. A significant reduction in the salinity of this wastewater contributed to sodium and chloride ion rejection rates of 93% and 79%, respectively, which is an important result for good reuse of the treated water in agriculture and domestic work.

Enhanced water permeability and antifouling properties of cross-linked graphene oxide composite membranes with tunable d-spacings

Low flux and membrane fouling are major challenges in membrane distillation (MD) for treating concentrated wastewater. This study compared the performance of GO composite membranes with different interlayer distances, by covalently bonding the terminal amine groups of ethylenediamine (EDA) and 1,12-diaminododecane (DADD) with the carboxyl groups present on the GO sheets. The results indicated that the GO-DADD/PTFE membrane, with longer carbon chain cross-linking, achieved the highest flux and antifouling properties. At 70 °C, the pure water flux reached 68.5 kg/m2·h, and the fluxes for treating NaCl, HA containing NaCl, and BSA containing NaCl were 29.8 %, 37.1 %, and 38.5 % higher than the uncrosslinked GO/PTFE, and 95.7 %, 121.2 %, and 146.9 % higher than the PTFE membrane, respectively. Through mathematical models for mass and heat transfer, the study identified the key to this enhancement as the increased d-spacing within the GO layer due to cross-linking, which weakened the Kelvin effect and enhanced the vapor partial pressure on the hot side. The unique surface structure and electrostatic interactions induced by long-chain cross-linking further boosted the antifouling effect. These modifications not only overcome the typical trade-off between retention rates and flux but also offer a scalable and efficient solution for advanced membrane distillation applications.

Fullerene in Water Remediation Nanocomposite Membranes—Cutting Edge Advancements

Among carbon nanoparticles, fullerene has been observed as a unique zero-dimensional hollow molecule. Fullerene has a high surface area and exceptional structural and physical features (optical, electronic, heat, mechanical, and others). Advancements in fullerene have been observed in the form of nanocomposites. Application of fullerene nanocomposites has been found in the membrane sector. This cutting-edge review article basically describes the potential of fullerene nanocomposite membranes for water remediation. Adding fullerene nanoparticles has been found to amend the microstructure and physical features of the nanocomposite membranes in addition to membrane porosity, selectivity, permeation, water flux, desalination, and other significant properties for water remediation. Variations in the designs of fullerene nanocomposites have resulted in greater separations between salts, desired metals, toxic metal ions, microorganisms, etc. Future investigations on ground-breaking fullerene-based membrane materials may overcome several design and performance challenges for advanced applications.

Correlating gas permeability and morphology of bio-based polyether-block-amide copolymer membranes by IR nanospectroscopy

The gas permeability of polymer membranes is determined by their nanoscale morphology, which strongly depends on the membrane fabrication. Here, we demonstrate how the correlation between gas permeability and fabrication-dependent nanoscale morphology of polymer membranes can be elucidated by infrared (IR) nanospectroscopy based on elastic IR scattering at an atomic force microscope tip. Specifically, we fabricated membranes of PEBAX® RNEW – a bio-based polyether-block-amide copolymer – by solvent casting and extrusion, achieving unprecedented CO2 permeability and CO2/N2 selectivity for the solvent-cast membranes. For the extruded membranes, however, we found an about 50 % reduced CO2 permeability, which could not be explained by differential scanning calorimetry and conventional IR spectroscopy. In contrast, IR nanospectroscopy revealed a highly crystalline polyether oxide (PEO) surface layer on the extruded membranes, not observed for the solvent-cast membranes. Annealing of the extruded membranes at 110 °C transformed the crystalline into amorphous PEO layers, as confirmed by IR nanospectroscopy, yielding a gas permeability close to that of the solvent-cast membranes. We thus attribute the dramatic gas reduction of the extruded membranes to their highly crystalline surface layers. Generally, studying polymer morphology by IR nanospectroscopy provides valuable information for better understanding the local gas permeability properties of polymer membranes.

Robust Electrostatic-Templated Polymerization for Controllable Synthesis of Stable and Permeable Polyelectrolyte Vesicles.

Polymer vesicles are of profound interest for designing delivery vehicles and nanoreactors toward a variety of biomedical and catalytic applications, yet robust synthesis of stable and permeable vesicles remains challenging. Here, we propose an electrostatic-templated polymerization that enables fabrication of polyelectrolyte vesicles with simultaneously regulated stability and permeability. In our design, cationic monomers were copolymerized with cross-linkers in the presence of a polyanionic-neutral diblock copolymer as a template. By properly choosing the block length ratio of the template, we fabricated a type of polyion complex vesicle consisting of a cross-linked cationic membrane, electrostatically assembled with the template copolymer which can be removed by sequential dissociation and separation under concentrated salt. We finally obtained stable polyelectrolyte vesicles of regulated size, membrane permeability, and response properties by tuning the synthesis factors including ionic strength, cross-linker type, and fraction as well as different monomers and concentrations. As a proof-of-concept, lipase was loaded in the designed cationic vesicles, which exhibited enhanced enzyme stability and activity. Our study has developed a novel and robust strategy for controllable synthesis of a new class of stable and permeable polymer (polyelectrolyte) vesicles that feature great potential applications as functional delivery carriers and nanoreactors.

Preparation and performance study of waste plastic blended ultrafiltration membrane

Waste plastic packaging bags (rPVC) and waste milk tea straws (rPLA) were used as membrane materials to prepare ultrafiltration (UF) membranes by the non-solvent induced phase separation (NIPS) method. The study aimed to investigate the influence of various factors, including different rPVC contents (10 wt%-20 wt%), membrane fractions (rPVC/rPLA), additive fractions (Pluronic F-127/PVP-K30), and different additive contents (0.5 wt%-3.0 wt%), on the performance of the membranes. The permeability, morphology, hydrophilicity, chemical composition, thermal stability, and antifouling properties of the blended UF membranes were thoroughly investigated. The experimental results revealed that the presence of rPLA and Pluronic F-127 increased the porosity, water absorption, pore size, and hydrophilicity of the blended UF membranes. Furthermore, the introduction of rPLA enhanced the thermal stability of the blended UF membranes. Additionally, the incorporation of Pluronic F-127 further improved the overall performance of the blended UF membranes. Specifically, it was found that the blended UF membranes achieved a pure water flux (PWF) of 192.50 L·m−2·h−1, while maintaining a bovine serum albumin (BSA) rejection rate of 95.20%. These results were obtained using a content ratio of rPVC/rPLA (90/10) at 14 wt% and an additive content of Pluronic F-127 at 2.5 wt%. By comparing with the blended UF membranes without introducing additives into the casting solution, the roughness (Ra) was reduced by 40.3%, the water contact angle (WCA) was reduced by 7.5%, the flux recovery rate (FRR) was increased by 80.5%, and the fouling resistance was enhanced.

Draft-free air conditioning through split membrane ceiling system: An exploratory study

The draft caused by convective air-conditioning is a primary contributor to thermal discomfort, particularly in localized cooling scenarios. While radiant systems offer a windless alternative, their condensation risks and maintenance costs bring concerns. In response, our research proposes an air-based radiation-convection hybrid system that’s draft-free and easy to implement. By suspending a breathable, flexible, textile-based membrane beneath the ceiling, the system mitigates drafts from ceiling-mounted air conditioners and leverages the membrane’s vast surface area for radiation. This work is an exploratory study focused on a retrofit split membrane system laying below the commercially packaged air conditioner (PAC). Three independent experimental studies were conducted. The first is a full-scale experiment assessing the membrane’s impact on PAC system operation and heat load management. The second is fundamental research to determine the permeation and airflow deceleration properties of different membranes. The third is a practical assessment in a self-study room retrofitted with the split membrane, aiming to determine the possibility of maintaining draft-free conditions. Results indicate that membranes with high laying ratios risk airflow short-circuiting. It can be reduced by adjusting the laying ratios and altering the laying pattern of the membrane, which also improves perimeter heat load management. Moreover, the permeation characteristics of various membrane materials were examined through flow and velocity attenuation coefficients. Besides material considerations, preliminary observations suggest that the membrane’s curvature could influence its permeation. Furthermore, the temperature and velocity data preliminarily affirmed the anti-draft performance of the split membrane ceiling system.

Preparation of N-MG-modified PVDF-CTFE substrate composite nanofiltration membrane and its selective separation of salt and dye.

Poly(vinylidene fluoride-co-chlorotrifluoroethylene) (PVDF-CTFE) is considered an ideal membrane material for the treatment of complex environmental water due to its exceptional thermal stability and chemical resistance. Thus, to expand its application in the field of nanofiltration (NF) membranes, in this study, N-methylglucamine (N-MG) was used to hydrophilically modify PVDF-CTFE, overcoming the inherent hydrophobicity of PVDF-CTFE as a porous substrate membrane, which leads to difficulties in controlling the interfacial polymerization (IP) reaction and instability of the separation layer structure. The -OH present in N-MG could replace the C-Cl bond in the CTFE chain segment, thus enabling the hydrophilic graft modification of PVDF-CTFE. The influence of the addition of N-MG on the surface and pore structure, wettability, permeability, ultrafiltration separation, and mechanical properties of the PVDF-CTFE substrate membrane was studied. According to the comparison of the comprehensive capabilities of the prepared porous membranes, the M4 membrane with the addition of 1.5 wt% N-MG exhibited the best hydrophilicity and permeability, indicating that it is a desirable modified membrane for use as an NF substrate membrane. The experiments showed that the rejection of Na2SO4 by the NF membrane was 96.5% and greater than 94.0% for various dyes. In the test using dye/salt mixed solution, this membrane exhibited a good separation selectivity (CR/NaCl = 177.8) and long-term operational stability.

Removal of silver colloids from radioactive wastewater by means of ultrafiltration

110mAg is the most common colloidal nuclide found in the radioactive liquid of nuclear power plants (NPPs). This paper investigates the morphology of silver colloids through a simulation experiment. The results show that the radionuclide 110mAg in the process water is reduced to Ag0 to form colloidal silver existing in regular shape with a size around 100 nm and a negative zeta potential. This zero-valent silver colloid can not be removed by the existing treatment process of ion exchange in NPPs effectively. One potential method for removal is ultrafiltration. The results demonstrate an effective removal of more than 98% of the silver colloids, accompanied by a flux increase of 146.9%. This is different from the traditional trade-off between membrane permeability and selectivity. Scanning electron microscopy (SEM) was utilized to study the membrane morphology, revealing a filtration mechanism that combines adsorption and sieving. The xDLVO theory was used to reveal the interfacial interaction between silver colloids and membrane materials. The results indicate that silver colloids can adsorb on the membrane surface spontaneously. The silver adsorbed by the membrane may form loose and hydrophilic silver colloids (an “aquifer”) and improve membrane hydrophilic and permeability properties simultaneously. The advantages of ultrafiltration on adsorption of silver colloids and improvement of water permeability provide a new method for the treatment of radioactive waste liquid containing colloidal silver.

Biological New Targets Prediction & ADME Pharmacokinetics Profiling of Newly Synthesized E / Z Isomers of Methyl 2-phenyl-2-(2-phenylhydrazono) Acetate Derivatives

Objective: In order to predict the pharmacokinetic properties, and new potential biological targets, biological targets prediction, and absorption, distribution, metabolism and excretion (ADME) profiling of newly synthesized Entgegen / Zusammen (E / Z isomers) of Methyl 2-phenyl-2-(2-phenylhydrazono) acetate derivatives were carried out. Methods: The prediction of new biological targets, pharmacokinetic properties, membrane permeability, and bioavailability radar properties were carried out by using Swiss Targets Prediction and Swiss ADME tools, respectively. Results: All the eight screened compounds possessed excellent drug-likeness criteria and passed successfully from Pan-assay interference compounds filter. Additionally, all screened compounds fell within the acceptable range in the bioavailability radar, showing excellent descriptors with a slight exceeding of insaturation properties. Compounds displayed elevated permeability across the Blood Brain Barrier, while compounds exhibited highest Human Intestinal Absorption according to the Egan Egg model. Moreover, the screened compounds also exhibited good pharmacokinetic properties. All the compounds exhibited activity against various enzymes, such as lyase, kinase, protease, and Family AG protein-coupled receptor. Conclusion: This conducted study smartly reveals that in-silico based studies were considered to provide robustness towards a rational drug design and development approach; therefore, in this way, it helps for further investigation of drug design and drug discovery steps.

Solute Transport through Mitochondrial Porins In Vitro and In Vivo.

Mitochondria are most likely descendants of strictly aerobic prokaryotes from the class Alphaproteobacteria. The mitochondrial matrix is surrounded by two membranes according to its relationship with Gram-negative bacteria. Similar to the bacterial outer membrane, the mitochondrial outer membrane acts as a molecular sieve because it also contains diffusion pores. However, it is more actively involved in mitochondrial metabolism because it plays a functional role, whereas the bacterial outer membrane has only passive sieving properties. Mitochondrial porins, also known as eukaryotic porins or voltage-dependent anion-selective channels (VDACs) control the permeability properties of the mitochondrial outer membrane. They contrast with most bacterial porins because they are voltage-dependent. They switch at relatively small transmembrane potentials of 20 to 30 mV in closed states that exhibit different permeability properties than the open state. Whereas the open state is preferentially permeable to anionic metabolites of mitochondrial metabolism, the closed states prefer cationic solutes, in particular, calcium ions. Mitochondrial porins are encoded in the nucleus, synthesized at cytoplasmatic ribosomes, and post-translationally imported through special transport systems into mitochondria. Nineteen beta strands form the beta-barrel cylinders of mitochondrial and related porins. The pores contain in addition an α-helical structure at the N-terminal end of the protein that serves as a gate for the voltage-dependence. Similarly, they bind peripheral proteins that are involved in mitochondrial function and compartment formation. This means that mitochondrial porins are localized in a strategic position to control mitochondrial metabolism. The special features of the role of mitochondrial porins in apoptosis and cancer will also be discussed in this article.

Hydrogen Crossover in Anion Exchange Membrane Fuel Cells

In recent years anion exchange membrane fuel cells (AEMFC) have started to draw more attention by potentially allowing catalysts based on more abundant materials, and by showing high performance [1]. One often overlooked parameter in these systems is membrane permeability of hydrogen, often referred to as hydrogen crossover, which directly affects fuel cell stability and efficiency. This undesirable effect creates mixed potential due to the permeated hydrogen reacting with oxygen on the cathode, and not generating useful electric energy, only water and heat [2]. The generated heat creates hotspots of temperatures enough to cause membrane defects or even destruction which further accelerates the degrading process [3].During fuel cell operation relative humidity (RH) and temperature varies in the system, therefore in this study hydrogen crossover is measured at different temperatures (between 50 and 70 ⁰C) and RH (between 30 and 100 %), on Aemion anion exchange membranes (AEMs) with and without reinforcement and with a variety of membrane thicknesses (25 and 50 μm in Figure 1. a). The hydrogen crossover is measured using a mass spectrometer (MS) at the inert gas exhaust. To avoid effects of other components pure membranes and gas diffusion layers (GDLs) were utilized without electrodes.It is shown that AEMs increase in permeability with temperature for all tested while the effect of RH depends on if they are reinforced or not (Figure 1. a). The non-reinforced membranes show a constant decrease in hydrogen crossover with increasing RH, while the reinforced show constant hydrogen crossover until full humidification where it sharply decreases. While the observed trends are different, the quantitative values between reinforced and non-reinforced membranes were relatively similar: at dry conditions, RHs lower than 50 %, crossover is 10 to 30 % lower for reinforced membranes, around 10 % higher at 70 % RH, and at full humidification a non-significant difference compared with non-reinforced (Figure 1. a). It is shown that an increase in the membrane thickness is not proportional to the decrease in hydrogen crossover, suggesting that interface resistance is not negligible. The calculated interface resistance is higher than the bulk resistance for both reinforced and non-reinforced membranes at all RHs (Figure 1. b). However, the bulk resistance is higher for reinforced membranes than for non-reinforced, while interface resistances are relatively similar. Interestingly, the ratio between the interface and the bulk resistance remains constant at all RHs. However, for the membranes without reinforcement the bulk resistance is 20 % of total crossover resistance, while for reinforced it is two times higher, 40 %. Scanning electron microscope (SEM) cross-section analysis shows that the reinforcement is a relatively thin layer of a different polymer in the membrane, which suggests that even a very thin reinforcement could affect membrane permeability properties. Understanding the effects of the reinforcement and their influence on fuel cells will allow for more durable and safer AEMFCs.Figure 1. H2 crossover measured using a MS at the inert gas side. a) At different temperatures, relative humidities and membrane thicknesses. b) H2 crossover resistance at the interface and in the bulk for membranes with and without reinforcement. Measurements are done at 70 °C and at flows 20 ml/min of both hydrogen and the inert gas (Ar).[1] D. R. Dekel, “Review of cell performance in anion exchange membrane fuel cells,” J. Power Sources, vol. 375, pp. 158–169, 2018, doi: 10.1016/j.jpowsour.2017.07.117.[2] S. S. Kocha, J. D. Yang, and J. S. Yi, “Characterization of Gas Crossover and Its Implications in PEM Fuel Cells,” 2006, doi: 10.1002/aic.10780.[3] Q. Tang, B. Li, D. Yang, P. Ming, C. Zhang, and Y. Wang, “Review of hydrogen crossover through the polymer electrolyte membrane,” Int. J. Hydrogen Energy, vol. 46, no. 42, pp. 22040–22061, 2021, doi: 10.1016/j.ijhydene.2021.04.050. Figure 1

Systematic investigation of MAX phase (Ti3AlC2) modified polyethersulfone membrane performance for forward osmosis applications in desalination

The current work presented an in-depth investigation of the design and fabrication of thin film membranes for desalination applications by forward osmosis (FO). This includes manipulating the substrate membrane structure aiming to optimize the final thin film composite membrane characteristics. In this context, the MAX phase (Ti3AlC2) as a 2D material has been harnessed to impart novel desirable traits on the prepared membrane. MAX phase has been impregnated in two disparate concentrations and three different scenarios including the substrate membrane and the polyamide layer in both the aqueous and organic phases during the interfacial polymerization. Membranes were comprehensively characterized by a series of experimental tools and methodologies including Atomic Force Microscopy, Scanning Electron Microscopy, Contact Angle, Fourier-transform infrared spectroscopy, pore size and porosity. Results disclosed that substrate membrane structure has a pivotal impact on final TFC/TFN membrane performance. Besides, the MAX phase (Ti3AlC2) could significantly enhance the morphological characteristics of the membrane and ultimately the performance in terms of water flux and reverse salt flux based on the content and the way impregnated. The permeation properties of the composite membranes were significantly superior to the pure PES membrane and the mean pore size also increased with the addition amount of MAX phase (Ti3AlC2) increased.

MXene-based membranes in water treatment: Current status and future prospects

Emerging highly selective MXene-based membranes have drawn a greater scientific interest in the field of water treatment due to their ion-selective and controlled molecular transport characteristics. However, MXene-based membranes have limitations in water treatment due to the difficulties including permeability-selectivity trade-off, swelling, fouling, oxidation, etc. Thus, a better understanding of the rational structural design principles of the membranes and their separation mechanisms are essential to further their development in water treatment. This review provides a concise overview of the key timeline in the fabrication of MXene-based membranes, the membrane characterization approaches used to understand their structure-property correlations, and the present difficulties in synthesizing high-performance MXene-based membranes. To overcome these challenges, new designing approaches are comprehensively reviewed to enhance the permeability, selectivity, stability, and antifouling properties of MXene-based membranes. These approaches include physical intercalation, chemical cross-linking, membrane surface modification, etc. Then, the separation mechanisms involved in the membranes in water treatment are presented, followed by the related applications. Looking forward, the perspective is provided on the future research directions for further advancing the membranes. This timely review may help to bridge the gap between academic research and industrial needs of MXene-based membranes for water treatment.

Gas permeation properties of bridged-type organosilica membranes at extremely low temperatures and the application to oxygen separation

A bridged-type organosilica, bis(triethoxysilyl)methane (BTESM) membrane was evaluated in detail for single-gas permeation at temperatures ranging from −130 to −200 °C, and for binary (O2/He, O2/N2) separation at 30 and -115 °C, respectively. The permeance of He, Ar, and N2 demonstrated a trend of activated diffusion as permeance increased with an increase in the temperature; O2 permeance, however, reached its maximum value at about −80 °C. O2 permeance increased with a decrease in the temperature (30 to −80 °C), and permeance then gradually decreased (−80 to −130 °C), which demonstrates surface diffusion. In the case of O2/He binary separation, both O2 and He permeated according to molecular sieving at 30 °C, but at −115 °C, O2/He selectivity was enhanced approximately 10-fold due to permeation blockage by adsorbed O2. On the other hand, in the case of O2/N2 binary separation at −115 °C, the effect of permeation blocking by adsorbed O2 permeance was lessened due to the effect of competitive adsorption, which translated to a level of O2/N2 selectivity that was only 1.5-fold higher than that at 30 °C.

Morphological effects of sphericalSiO2and hexagonal mesoporousMCM‐41 nanoparticles in polyacrylonitrile mixed matrix membranes on the biofouling mitigation in short‐term filtration

AbstractIn this study, the morphology of the nanostructures is evaluated on the surface characterization and performance of the polyacrylonitrile (PAN) ultrafiltration mixed matrix membranes (MMM). To this end, silica nanoparticles (NPs) such as spherical (SiO2) and hexagonal mesoporous (MCM‐41) with high hydrophilicity were incorporated at 0.5, 1, and 2 wt%. Attenuated total reflectance‐Fourier transform infrared analysis illustrated the placement of NP on the surface of the MMM. Atomic force microscopy studies also showed that SiO2NP added to PAN exhibited a smoother surface than MCM‐41 NP. Field‐emission scanning electron microscope analysis of the MMM identified that all membranes are composed of a finger‐like porous structure. Contact angle measurements indicate that the morphology of the NPs has no significant effect on MMM hydrophilicity. Moreover, the performance of the MMM was evaluated, and regardless of NP morphology, the MMM showed better permeate flux with increased loading. A higher pure water flux was observed in the PAN‐MCM41‐1% membrane (237 L/m2 h), possibly because of inherent porosity and high hydrophilicity of MCM‐41 compared to SiO2NP. Further, the PAN‐SiO2‐1% membrane exhibited superior antifouling properties due to a lower surface roughness. The present studies reveal that the morphology of the NP greatly influence on the structure, permeation, and antifouling properties of PAN membranes.

Acid mine drainage (AMD) treatment using a novel tannic acid functionalized Boehmite/polyether sulfone nanofiltration membrane

This study focuses on the fabrication of TA-BM/PES membranes by the incorporation of tannic acid functionalized Boehmite nanoparticles into the PES membrane matrix through the phase inversion technique. The presence of TA-BM nanoparticles in the TA-BM/PES membranes was confirmed by analysis of the FT-IR spectra of the embedded membranes. The hydrophilicity, permeability, surface morphology, and fouling resistance properties of membranes modified with TA-BM nanoparticles were compared to those of the naked membrane. The fouling behavior of the modified membranes was assessed in the presence of a foulant solution containing 200 ppm BSA (bovine serum albumin) and 200 ppm Na2SO4. The flux recovery ratio results showed an improvement in all modified membranes, especially M2 membrane. The modified membranes shown remarkable efficiency in the rejection of heavy metal ions (over 72 %), sulfate (over 80 %), and salt (Na2SO4 > 84 % and NaCl>48 %). The M2 membrane was chosen as the most suitable membrane and shown effective performance in eliminating heavy metals (Fe2+ = 65.5, Mn2+ = 88.8, Mg2+ = 83.5 and Ca2+ = 78.6 %) as well as sulfate (SO42− = 83.5 %) from a synthetic acid mine drainage (AMD) wastewater. Based on the findings presented in this research, it can be concluded that the TA-BM/PES nanofiltration membrane has potential for effective use in the treatment of AMD wastewater.

Mixed matrix membrane based on PEBAX® filled with layered double hydroxides

The effect of incorporating layered double hydroxide (LDH) nanoparticles containing different molar ratios of metals on the thermal, mechanical, and gas permeation properties of membranes based on PEBAX® was evaluated. The three nanoparticles were synthesized using molar x-ratios (x = Al/(Mg + Al)) equal to 0.20, 0.25 and 0.33. The dispersed nanoparticles changed thermal resistance, improved mechanical properties and CO2/CH4 separation performance of MMM when compared to the membranes of neat PEBAX®. The addition of 2 % of LDH in PEBAX® 1657 promoted an increase of about 17 % in the elastic modulus and 10 % in the stress at break. The best result of permeation tests (1657–0.33–5 % MMM at 0.5 bar), shows increase CO2 permeability by 44 % and CO2/CH4 selectivity by 115 % as compared to the neat material. Gas permeation results showed that LDH with more anions favors the facilitated transport of CO2.