Mixed Membranes Research Articles

α-Synuclein interaction with POPC/POPS vesicles.

We have investigated the adsorption of the amyloid-forming protein α-Synuclein (αSyn) onto small unilamellar vesicles composed of a mixture of zwitterionic POPC and anionic POPS lipids. αSyn monomers adsorb onto the anionic lipid vesicles where they adopt an α-helical secondary structure. The degree of adsorption depends on the fraction of anionic lipid in the mixed lipid membrane, but one needs to consider the electrostatic shift of the serine pKa with increasing fraction of POPS. The vesicles with adsorbed αSyn monomers are kinetically stable. However, after fibrils have been formed, here triggered by the addition of a small concentration of pre-formed fibrils (seeds), we observed that the average vesicle size increased by approximately a factor of two. This increase in the vesicle size can be explained by vesicle fusion taking place during the fibril formation process.

Opposite Roles of Cholesterol and Lanosterol in Lipid Membrane on Amyloid-Beta 42 Peptide Nucleation and Fibril Formation.

Molecular self-assembly of amyloid-beta peptides to form fibrillar aggregates is a known cause of Alzheimer's disease. Although homogeneous nucleation of amyloid-beta is unfavorable, heterogeneous nucleation of amyloid-beta in cell membranes plays a key role in fibril formation. We observed these opposite roles in the effects of cholesterol and lanosterol, the precursor of cholesterol in the brain, on nucleation. As previously reported, cholesterol accelerated nucleation, whereas lanosterol decelerated it when mixed with dioleoyl-phosphatidylcholine at 20%. The observed opposite effects of cholesterol and lanosterol on nucleation do not correlate with the differences in the mechanical and thermodynamic nature of mixed membranes. However, the affinity of amyloid-beta to the inner membrane seems to be related to the opposite effects on nucleation kinetics. Cholesterol reduced the insertion of amyloid-beta into the lipid membrane, whereas lanosterol promoted the insertion of amyloid-beta into the membrane, which would make amyloid-beta more tightly bound by lipid molecules and reduce its diffusivity in the membrane and consequently inhibit nucleation. Our study provides insights into the effects of sterol compounds other than the well-investigated cholesterol on the self-assembly of amyloid-beta to clarify the molecular basis underlying Alzheimer's disease pathology and to develop targeted therapeutic strategies.

Facile green treatment of mixed cellulose ester membranes by deep eutectic solvent to enhance dye removal and determination.

Synthetic dye production and the consequent generation of dye-rich wastewater are major concerns of water quality in many countries. We developed a sustainable approach with deep eutectic solvent (DES) treatment to enhance the efficiency of mixed cellulose ester (MCE) membrane-based dye removal material. The DES composition and treatment conditions were optimized, and the treated membranes were comprehensively characterized. DES-treated membranes exhibited improved morphology, surface properties, and superior dye adsorption capabilities. Our study revealed that the adsorption process was chemically controlled and driven by electrostatic and hydrogen bond interactions. Thermodynamic analysis confirmed the endothermic and spontaneous nature of the adsorption process. Moreover, the treated membranes exhibited good separation performance for dye/salt mixtures. Additionally, we demonstrated selective adsorption of cationic dyes over anionic dyes using these treated membranes. This selectivity enabled the development of a membrane solid-phase extraction (MSPE) method for quantification of trace amount of dyes. Compared with other methods, DES-treated MCE membranes present a promising solution for efficient dye quantification and removal, offering a green and effective strategy to address water pollution stemming from synthetic dyes. Additionally, this study provides a novel strategy for green chemistry modification of cellulose-based materials.

Effects of Different Concentrations of AmB on the Unsaturated Phospholipid-Cholesterol Membrane Using the Langmuir Monolayer and Liposome Models.

Amphotericin B (AmB) causes toxicity to the erythrocyte membrane, leading to hemolysis, which limits the clinically effective dose for AmB intravenous therapy in invasive fungal infections. The molecular mechanism by which AmB adheres to the membrane of erythrocytes is the key factor in causing AmB to be toxic to the membrane of erythrocytes, but it is not yet fully understood; the mechanism by which AmB adheres to the liquid microdomains with higher fluidity formed by cholesterol and unsaturated phospholipids remains especially unclear. This study examined the adsorption of AmB at different concentrations, 5, 45, 85, and 125 μg/mL, on unsaturated phospholipid membranes containing 50 mol% cholesterol. The thermodynamic properties and structure of DOPC monolayers and DOPC/cholesterol mixed monolayers at different concentrations of AmB have been investigated using the Langmuir monolayer model and the BAM method. The impact of varying concentrations of AmB on the hydrophilic and hydrophobic domains of the DOPC bilayers and the DOPC/cholesterol mixed bilayers have also been discussed using large unilamellar vesicle liposomes and fluorescence techniques. It is shown that for AmB concentrations greater than 5 μg/mL, with an increase in AmB's concentration, the reorganization time for the DOPC/cholesterol monolayer increases, and the elastic modulus of the DOPC/cholesterol mixed monolayer decreases. In particular, when AmB's concentration is higher than 85 μg/mL, the liquid-condensed phase domains on the DOPC/cholesterol monolayer reduce significantly and the liquid-expanded phase domain enlarges from the BAM images. When the AmB concentration reaches 5 μg/mL, the disorder of the hydrophobic and hydrophilic domains of the DOPC/cholesterol bilayer increases as the AmB concentration increases. The way in which AmB interacts with the DOPC/cholesterol mixed membrane is related to the concentration of AmB. The higher the concentration of AmB, the more likely it is to remove cholesterol from the unsaturated phospholipid membrane. The results are helpful to understand the mechanism of AmB's toxicity to the erythrocyte's membrane, which has a guiding value for seeking ways to reduce the AmB's toxicity.

Biobased Proton Exchange Membrane Using an Anionic Nanocellulose System

As integral parts of fuel cells, polymer electrolyte membranes (PEM) facilitate the conversion of hydrogen’s chemical energy into electricity and water. Such energy-conversion devices require stability, high ionic conductivity, and good water uptake and mechanical properties, while being cost-effective and sustainable. Nanocellulose membranes, which are promising materials for PEMs, present all the requirements except high ionic conductivity. The introduction of negative charges or other components such as nanoparticles or conductive polymers in the nanocellulose membranes structures is a promising solution to increase ionic conductivity in these bio-based materials. Here, our target is to understand how we can improve the ionic conductivity of nanocellulose materials while retaining thermal and mechanical properties. We produced negatively charged nanocellulose fibril (CNF) membranes (TEMPO-CNF and sulfonated-CNF) that present different functional groups and acidity (pKa COO-: ~3-4 and pka SO3-: ~7) which leads to differing ionic conductivities. We also studied the synthesis of these two nanocelluloses in a mixed membrane containing 1:1 TEMPO-CNF: sulfonated-CNF and how the membrane structure (porosity and thickness) impacts the ionic conductivity. All bio-based PEMs exhibited an impressive thermal stability up to 190 °C and high mechanical properties with a maximum Young’s modulus of around 1.15GPa, tensile strength of 0.18GPa, and storage modulus over 13GPa, as well as a high hydrophilicity with a water uptake as high as 6334%. These results are comparable to bio-based membranes mentioned in the literature and to commercially available membranes. Utilizing modified CNFs as a bio-based template for a commercial PEM would reduce costs, improve sustainability, and valorize cellulose through a new, high value application. The intrinsic renewability and tunability of cellulose-derived materials makes them promising candidates to meet the demands of novel sustainable energy solutions, and these bio-based membranes hold the potential for further enhancement through optimizing support structure materials, blend compositions, and production techniques. Figure 1

Enhanced performance and anti-fouling properties of polyether sulfone (PES) membranes modified with pistachio shell-derived activated carbon (PSAC)@ZIF-8&ZIF-67 to remove dye contaminants

This study aims to improve the properties of polyether sulfone (PES) membranes by using an innovative composite filler. Pistachio shell-derived activated carbon (PSAC) was initially synthesized via chemical activation, followed by surface modification with ZIF-8 and ZIF-67. Subsequently, modified membranes with varying weight percentages of this composite were fabricated using the phase inversion method. The PSAC@ZIF-8&ZIF-67/PES membranes were characterized through FESEM, AFM, pore size, zeta potential, porosity, and water contact angle analyses. The incorporation of the composite in the membranes was confirmed through ATR-FTIR, XRD, and EDS mapping analyses. The finding indicated that adding 0.6 wt% of nanoparticles improved membrane hydrophilicity, increased surface charge, and enhanced porosity. Additionally, the mixed membranes exhibited reduced sedimentation and higher dye removal than unmodified membranes. The optimum amount of composite is determined as 0.6 wt%. At this condition, pure water flux (PWF) increased dramatically from 22.56 L/m2h to 96.26 L/m2h. The mixed matrix membrane demonstrated superior efficiency in removing malachite green (MG) (97 %) and crystal violet (CV) dyes (93 %) and achieved the highest recovery ratio of 61.9 %, indicating a more remarkable membrane ability to combat fouling. The developed membrane demonstrated enhanced hydrophilicity, dye removal efficiency, and antifouling properties, making it promising for environmental applications.

A study of H2O opposite-direction permeation through a mixed ceramic-molten salt CO2 separation membrane

Ceramic-molten salt dual-phase CO2-permselective membrane is a promising technology to capture CO2 at high temperatures. The formation of hydroxide (OH−) phase in molten carbonate (CO32−) in the presence of steam leads to an increase in CO2 permeation flux. However, few works have paid attention to the H2O permeability. In this study, we find that there are two routes for H2O permeation through the molten hydroxide-based dual-phase membrane with a wet sweep gas; one route is permeated with CO2, but in the opposite direction; the other is a separate route for H2O permeation through the interaction of oxygen ions and hydroxide ions. The resulting H2O fluxes are 5.3 and 1.7 times the fluxes of CO2 at 600 and 800 °C, respectively. Stable CO2 and H2O fluxes are obtained over 100 h at 700 °C, making the dual-phase membrane promising for coupling CO2 capture with conversion processes.

Mixed matrix PVDF microfiltration membranes with in-situ synthesized polyethyleneimine particles as a platform for flow through, high capacity, weak base and salt tolerant anion exchange membrane adsorbers for downstream bioprocessing

The rapid growth of the monoclonal antibody (mAb) therapeutic market has led to a need for improved downstream bioprocessing, including mAb capture and release from bioreactor harvests followed by product purification and polishing. Membrane chromatography (MC) is poised to displace resin-based column chromatography in mAb product polishing. To remove negatively charged product impurities (e.g., host cell proteins, DNA, viruses, and endotoxins), anion exchange (AEX) membrane adsorbers offer higher process rates and eliminate the risks of cross contamination as they can be deployed as single use separation devices, which are increasingly being utilized in downstream bioprocessing to increase manufacturing speed and decrease production cost. Here, we describe a one-pot and single step phase inversion casting process for the preparation of a family of mixed matrix polyvinylidene fluoride (PVDF) microfiltration (MF) membranes with in-situ synthesized polyethyleneimine (PEI) microparticles that can serve as flow through, high capacity, and salt tolerant weak base AEX membrane adsorbers. These new membranes have a high content of weak base (WB) groups (primary and secondary amines) by virtue of the utilization of bis(2-chloroethyl)amine hydrochloride (BCAH) as crosslinker in the in-situ synthesis of PEI microparticles in the dope dispersions prior to membrane casting. By varying the concentration of PEI and BCAH in the casting dispersions, we successfully utilized nonsolvent induced phase separation (NIPS) with isopropyl alcohol as the nonsolvent in the membrane coagulation bath to prepare a mixed matrix PVDF-PEI MF membrane with (i) a relatively uniform and open microstructure in which the PEI particles completely cover the PVDF spherulites present at the membrane surface and cross section, (ii) high water flux (>1000 liters/m2/hr. at 2 bar) and (iii) a high loading of BCAH crosslinked PEI microparticles (51.0 wt%) containing weak base primary, secondary, and tertiary amine groups. The protein binding measurements show that this new mixed matrix PVDF-PEI MF membrane can serve as a flow through, high capacity, and salt tolerant WB AEX membrane adsorber with a bovine serum albumin (BSA) dynamic binding capacity of ∼60 mg BSA per mL of membrane in a 50 mM TRIS buffer containing 100 mM of NaCl (15 mS/cm) at 10 % breakthrough and flow rate of 10 MV/min. The overall results of this study indicate that our mixed matrix PVDF-PEI MF membranes with in-situ synthesized and BCAH crosslinked PEI microparticles have a promising potential to serve as a platform for the design, preparation, and scale up of a new generation of flow through, high capacity, salt tolerant, WB AEX membrane adsorber materials for downstream bioprocessing.

Intensifying the CO2/N2 separation performance of PVAm membrane by amine-functionalized porous montmorillonite

Multilayered montmorillonite (MMT) exhibits the building block stacking in polymer matrix, which has tortuous transport passageways and a few CO2 affinity sites, thus mixed matrix membranes incorporated with MMT have low molecular recognition ability for CO2. Herein, the porous MMT (p-MMT) was initially prepared through the solid-phase desilication reaction, and then amine-functionalized p-MMT (P3.2@p-MMT) was synthesized by the electrostatic interaction between positively charged polyethyleneimine (PEI) and negatively charged p-MMT, in which PEI was confined within the pore. Subsequently, mixed matrix composite membranes (MMCMs) were developed by the dispersion of polyvinylamine (PVAm) and P3.2@p-MMT, as well as hydrophilic-modified polysulfone as a support. It was observed that P3.2@p-MMT was uniformly dispersed in polymer matrix, and two phases had good interfacial compatibility due to hydrogen bonding. As a result, the gas separation performance of as-prepared MMCMs achieved a CO2 permeance of 217 GPU with a CO2/N2 selectivity of 112.3, which were 2.97 and 2.45 times that of the pristine PVAm membrane, and 1.57 and 2.49 times that of MMCMs incorporated with p-MMT respectively. The excellent gas separation performance is attributed to the relatively straight transport passageways, which originates from P3.2@p-MMT. Moreover, the amine groups within the pore of P3.2@p-MMT facilitate CO2 transport in the MMCMs. In addition, as-prepared MMCMs had high stability during over 360 h-testing, which displayed an average CO2 permeance of 238 GPU with the CO2/N2 selectivity of 124.1 utilizing a gas mixture as the feed gas.

Co-doped Zr-UiO-66-NH2@carboxylated cellulose nanocrystals/PAN membrane for oil/water separation with photocatalysis-PMS synergistic self-cleaning and antibacterial activity

The development of superwetting membranes is a promising approach for separating emulsified oily wastewater. However, challenges such as low flux without external pressure and membrane fouling have hindered membrane performance. Herein, we fabricated a novel nanofibrous membrane by grafting Co-doped Zr-UiO-66-NH2 (UiO(Zr/Co)) nanoparticles onto carboxylated cellulose nanocrystals (CCNC)-polyacrylonitrile (PAN) mixed matrix electrospinning membrane via chemical bonds through EDC/NHS reaction. CCNC served a dual purpose by enhancing membrane hydrophilicity and providing connection points for UiO(Zr/Co). The as-prepared UiO(Zr/Co)@CCNC/PAN exhibited superhydrophilic/underwater superoleophobic and anti-fouling properties. The membrane demonstrated excellent demulsification and gravity-driven separation capabilities for various oil-in-water emulsions, with superior permeation flux (1588–2557 L m−2 h−1) and separation efficiency (above 99 %). Furthermore, UiO (Zr/Co)@CCNC/PAN could activate peroxomonosulfate (PMS) under visible light to remove both high viscous crude oil-fouling and bio-fouling, exhibiting impressive photocatalytic self-cleaning and antibacterial activity. The generation of reactive radicals (O2−, OH and SO4−) and non-radical (1O2) species in UiO(Zr/Co)@CCNC/PAN+PMS system through multiple pathways was confirmed. Additionally, the band structure of UiO(Zr/Co) and synergistic photocatalytic-PMS activation mechanism were investigated. This work provides new insights into the design and fabrication of MOF modified superwetting nanofibrous membrane with inherent bonding, high permeation flux, anti-fouling and self-cleaning properties.

Ultra-high Prussian blue loading in SPEEK matrix fabricated by one-step electrostatic spraying as proton exchange membranes for fuel cell

Mixed matrix proton exchange membrane is promising for fuel cell application, but maximizing nanofiller loading to enhance performance is significant challenge. This study developed a one-step electrostatic spraying strategy to prepare ultra-high Prussian blue loading (up to 66.7 wt%) in sulfonated poly(ether ether ketone) matrix (PB@SPEEK). By coupling the electrostatic spraying and in situ solvent evaporation densification, SPEEK fills the voids between PB nanoparticles, forming a bicontinuous microstructure in the membrane. The ultra-high PB content of 66.7 wt% enable a fully utilization of its intrinsic properties, resulting in extremely low swelling ratio of 3.4% at 80°C, excellent flexibility of freely folding, and nearly 100% mass retention after 12-hour immersion in Fenton reagent at 60°C. In single-cell tests, the PB@SPEEK mixed matrix membrane shows stable internal resistance due to easily water hydration, therefore achieving excellent low-temperature peak power (1973.9 mW/cm2 at 40 °C and 2078.0 mW/cm2 at 60°C). The strategy developed in this study enables the one-step preparation of large-area, ultra-thin and ultra-high capacity of inorganic nanofiller mixed matrix proton exchange membranes for high-performance fuel cell.

Clarification of apple juice using cold plasma treated mixed cellulose esters membrane: Flux modeling, membrane fouling, and juice physicochemical properties evaluation

This study aimed to clarify apple juice using unmodified and low-pressure cold plasma (gas: air, power: 10 W, and exposure time: 180 s) surface-modified mixed cellulose esters (MCE) microfiltration membranes. The effect of feed pressure (20, 40, and 60 kPa), feed flow rate (10, 15, and 20 mL/s), and feed temperature (27 and 40 °C) on the permeate flux was evaluated using response surface methodology (RSM). The binary interaction of feed pressure and temperature and the second-order (non-linear) interaction of feed pressure and flow rate had a significant effect on the permeate flux (P < 0.05). Generally, the process at 60 kPa, 15 mL/s, and 40 °C resulted in the maximum permeate flux. The cold plasma surface modification of the MCE membrane increased the permeate flux by about 45% at the optimum process conditions. Evaluation of membrane fouling showed that the cake formation was the predominant membrane fouling mechanism during both membrane processing. The physicochemical properties evaluation revealed that the surface-modified membrane produced clarified apple juice with antioxidant activity, reducing sugars, total sugars, phenolic, and vitamin C contents about 18.87%, 12.9%, 15.49%, 24.53%, and 45.15% more than clarified apple juice produced with unmodified MCE membrane, respectively.

Preparation of TA-O-MoS2/PES mixed matrix ultrafiltration membrane for rare earth wastewater treatment

The trade-off between permeability and selectivity, along with the issue of membrane fouling, has constrained the widespread application of ultrafiltration (UF) membranes in recycling rare earth wastewater. Here, we present the incorporation of tannic acid (TA) modified molybdenum disulfide oxide (O-MoS2) as a functional enhancer to fabricate polyethersulfone (PES) based mixed matrix membranes through a nonsolvent induced phase separation (NIPS) approach. Compared to the unmodified PES membrane, the integration of TA-O-MoS2 significantly improves the hydrophilicity, porosity in the mixed matrix membrane. By altering the concentration of TA-O-MoS2, the TA-O-MoS2/PES UF membrane achieves enhanced hydrophilicity and charge properties, resulting in a remarkable improvement in separation performance. Specifically, the optimized membrane M2 (TA-O-MoS2 addition of 0.1 wt%) exhibits a water flux of 140.98 Lm−2h−1bar−1 and a PEG 20000 rejection rate of 91.00 %, representing increases of 180 % and 120 % over the control PES membrane, respectively. Notably, membrane M2 effectively retains 91.31 % of macromolecular organic compounds in rare earth wastewater, while permitting nearly complete passage of inorganic salts, for instance CaCl2 (3.26 %) and MgSO4 (4.84 %). Moreover, the TA-O-MoS2/PES membrane demonstrates robust antifouling properties and exceptional durability, indicating its significant potential for efficient treatment and resource recovery in rare earth wastewater.

THE EFFECT OF SODIUM DEOXYCHOLATE AND TWЕЕN-20 ON THE ACTIVITY AND PROPERTIES OF NA+/K+-ATPase IN THE MIXED MEMBRANE FRACTION OF THE CEREBRAL CORTEX OF RATS

Interoduction. The present work extends the understanding of the activity of ouabain-sensitive (α2 and α3) and ouabain-resistant (α1) Na+/K+-ATPase isoforms in the mixed membrane fraction of rat cerebral cortex in the presence of various detergents. The aim of the study: to determine the activity of ouabain-sensitive (α2 and α3) and ouabain-resistant (α1) Na+/K+-ATPase isoforms by changing the concentration of Mg+2 ions in the incubation medium and using the detergents sodium deoxycholate and Tween-20. Material and methods. To determine Na+/K+-ATPase activity, we used the method of A. Kazennova et al. The reaction was triggered by adding ho-mogenate of cerebral cortex incubated with detergents; the samples were incubated for 30 minutes in a water bath at 370 C. The activity of ouabain-sensitive isoforms was determined by adding 200 μmol of ouabain to the incubation mixture. The activity of ouabain-sensitive isoforms was deter-mined by adding 200 μmol ouabain to the incubation mixture, and the activity of ouabain-resistant isoforms was determined as the difference between the total Na+/K+-ATPase activity and the activity of ouabain-sensitive isoforms. ATPase activity was determined by inorganic phosphate (Pi) increment as the difference between total ATPase activity, magnesium ATPase activity, in reaction with ammonium molybdate and tin chloride in the presence of ascorbic acid as a reducing agent. Results. At optimal concentrations of detergents Dox-Na (1.25 mg/mL) and Tween-20 (6.5 mg/mL), both ouabain-sensitive and ouabain-resistant Na+/K+-ATPase isoforms are characterized by normal activity dynamics from the concentration of Mg2+ ions. Consequently, the use of detergents at given concentrations does not change the ability of enzymes to conformational rearrangements during the reaction cycle. It was found that both used detergents allow to reveal a significant percentage of latent activity of ouabain-sensitive (α2 and α3) and ouabain-resistant (α1) Na+/K+-ATPase isoforms in the mixed mebran fraction of the cerebral cortex of rats. Conclusion. The study of Mg2+-dependent properties revealed a similar character of the curves of dependence of enzyme activity on the concentra-tion of Mg2+ in the incubation medium for all Na+/K+-ATPase isoforms studied

Synthetic membrane selection for in vitro release testing (IVRT): A case study of topical mometasone furoate semi-solid dosage forms

In vitro release testing (IVRT) is extensively used to develop the formulation of topical semi-solid products, to evaluate the quality and consistency of the product after scale-up and post-approval changes, and more recently to aid the evaluation of topical generic products’ equivalency. The selection of synthetic membrane is one of the most critical parameters of the method development part of IVRT. It is well known that the membrane features namely its polymer matrices, porosity, pore size, thickness can have a substantial effect on the IVRT data. However, there is no detailed information available in the literature regarding the membrane selection for different types of topical dosage forms. Therefore, we aimed to investigate whether difference topical semi-solid dosage forms of the same drug molecule would cause to variation in the membrane selection. Within this framework, rheological behaviour of commercially available three different types of topical semi-solid dosage forms (ointment, cream, and lotion) of mometasone furoate (0.1%) were primarily characterized. Then, the membrane inertness test was conducted using a series of synthetic hydrophilic membranes (regenerated cellulose, cellulose acetate, cellulose nitrate, mixed cellulose ester membranes) and hydrophobic membranes (polyether sulfone, polypropylene, polytetrafluoroethylene membranes) after identifying of an appropriate receptor medium that ensures sink condition for mometasone furoate. Lastly, IVRT studies from the topical semi-solid products were performed utilizing Franz-type diffusion cells. The membrane inertness and in vitro release data demonstrated that the cellulose acetate membrane showed superior diffusion properties in general while the other synthetic membranes exhibited varying outcomes for different semi-solid dosage forms of mometasone furoate. Overall, the results indicated that the release rate and the cumulative drug released amount of drug after 6 h through the different synthetic membranes might vary depending on the semi-solid dosage form. In order to select the synthetic membrane for IVRT, it should also be considered potential interactions between the polymer matrices and the chemical structure of drug molecule as well as formulation components prior to conducting membrane inertness test and IVRT studies.

Surface treatment optimization of mixed cellulose ester membrane by cold plasma treatment to improve apple juice clarification

This study aimed to determine the optimal conditions for the surface modification of mixed cellulose ester (MCE) microfiltration membrane by cold plasma (CP) for apple juice clarification. Response surface method using central cubic design (CCD) was employed for the optimization of the membrane surface modification process. Plasma gas type (oxygen, carbon dioxide, and air), power (10, 15, and 20 W), and exposure time (120, 180, and 240 s) were used as the factors for cold plasma surface modification. The results revealed the surface modification of the MCE membrane using air as plasma gas with plasma power and exposure time equal to 10 W and 180 s resulted in the maximum permeate flux in apple juice clarification. The results of scanning electron microscope, and atomic force microscope confirm the effect of CP treatment on the membrane surface roughness. Fourier transform infrared spectroscopy showed the incorporation of the hydroxyl group into the membrane surface due to CP treatment which affected the surface contact angle and hydrophilicity. The CP treatment of the membrane significantly affects the membrane resistances. Also, the surface modification of the MCE membrane using the CP treatment process in optimal conditions is an effective method for clarifying apple juice.

Fabrication of TiO2@ZIF-67 metal organic framework composite incorporated PVDF membranes for the removal of hazardous reactive black 5 and Congo red dyes from contaminated water

Novel application of TiO2@ZIF-67 composite incorporated poly (vinylidene fluoride) (PVDF) mixed matrix flat-sheet membranes for treating the water contaminated with hazardous reactive black 5 and congored dyes was the crux of this work. The composite was characterized by FTIR, BET, XRD, zeta potential and particle size, and TGA. The as-synthesized composite was embedded in the PVDF polymeric matrix and flat-sheet-membranes were fabricated adopting the NIPS method followed by the different characterizations like scanning electron microscopy, EDS, elemental mapping, contact angle, atomic force microscopy, surface energy, and XPS. Results of the performance studies showed an enhanced pure water permeability from 150.99 Lm-2h−1 for neat membrane to 261.39 Lm-2h−1 for TZM-2. The reactive black 5 dye was rejected in 97.4 %, 92.2 %, and 84.84 % in acidic, basic and neutral conditions respectively by TZM-2 membrane. Whereas, the PVDF membranes without the composite showed rejections of 83.19 %, 82.5 %, and 72.1 % respectively in acidic, basic, and neutral conditions. The Congo Red dye was rejected in 89.4 %, 95.68 %, and 92.4 % in acidic, neutral and basic conditions respectively by TZM-2 membranes. Whereas, the PVDF membranes without the composite showed rejections of 82.8 %, 91.9 %, and 85.4 % respectively in acidic, neutral and basic conditions.

Optimizing Archaeal Lipid Biosynthesis in Escherichia coli.

Membrane lipid chemistry is remarkably different in archaea compared with bacteria and eukaryotes. In the evolutionary context, this is also termed the lipid divide and is reflected by distinct biosynthetic pathways. Contemporary organisms have almost without exception only one type of membrane lipid. During early membrane evolution, mixed membrane stages likely occurred, and it was hypothesized that the instability of such mixtures was the driving force for the lipid divide. To examine the compatibility between archaeal and bacterial lipids, the bacterium Escherichia coli has been engineered to contain both types of lipids with varying success. Only limited production of archaeal lipid archaetidylethanolamine was achieved. Here, we substantially increased its production in E. coli by overexpression of an archaeal phosphatidylserine synthase needed for ethanolamine headgroup attachment. Furthermore, we introduced a synthetic isoprenoid utilization pathway to increase the supply of isopentenyl-diphosphate and dimethylallyl diphosphate. This improved archaeal lipid production substantially. The archaeal phospholipids also served as a substrate for the E. coli cardiolipin synthase, resulting in archaeal and novel hybrid archaeal/bacterial cardiolipin species not seen in living organisms before. Growth of the E. coli strain with the mixed membrane shows an enhanced sensitivity to the inhibitor of fatty acid biosynthesis, cerulenin, indicating a critical dependence of the engineered E. coli strain on its native phospholipids.

Mixed-Matrix Organo-Silica-Hydrotalcite Membrane for CO2 Separation Part 1: Synthesis and Analytical Description.

Hydrotalcite exhibits the capability to adsorb CO2 at elevated temperatures. High surface area and favorable coating properties are essential to harness its potential for practical applications. Stable alcohol-based dispersions are needed for thin film applications of mixed membranes containing hydrotalcite. Currently, producing such dispersions without the need for delamination and dispersing agents is a challenging task. This work introduces, for the first time, a manufacturing approach to overcoming the drawbacks mentioned above. It includes a synthesis of hydrotalcite nanoparticles, followed by agent-free delamination of their layers and final dispersion into alcohol without dispersing agents. Further, the hydrotalcite-derived sorption agent is dispersed in a matrix based on organo-silica gels derived from 1,2-bis(triethoxysilyl)ethane (BTESE). The analytical results indicate that the interconnection between hydrotalcite and BTESE-derived gel occurs via forming a strong hydrogen bonding system between the interlayer species (OH groups, CO32-) of hydrotalcite and oxygen and silanol active gel centers. These findings lay the foundation for applications involving incorporating hydrotalcite-like compounds into silica matrices, ultimately enabling the development of materials with exceptional mass transfer properties. In part 2 of this study, the gas separation performance of the organo-silica and the hydrotalcite-like materials and their combined form will be investigated.

Modulation of Interlayer Nanochannels via the Moderate Heat Treatment of Graphene Oxide Membranes.

In response to the phenomenon of interlayer transport channel swelling caused by the hydration of oxygen-containing functional groups on the GO membrane surface, a moderate heat treatment method was employed to controllably reduce the graphene oxide (GO) membrane and prepare a reduced GO composite nanofiltration membrane (mixed cellulose membrane (MCE)/ethylenediamine (EDA)/reduced GO-X (RGO-X)). The associations of different heat treatment temperatures with the hydrophilicity, interlayer structure, permeability and dye/salt rejection properties of GO membranes were systematically explored. The results indicated that the oxygen-containing groups of the GO membrane were partially eliminated after heat treatment, and the hydrophilicity was weakened. This effectively weakened the hydration between the GO membrane and the water molecules and inhibited the swelling of the oxidized graphene membrane. In the dye desalination test, the MCE/EDA/RGO membrane exhibited an ultra-high rejection rate of over 97% for methylene blue (MB) dye molecules. In addition, heat treatment increased the structural defects of the GO membrane and promoted the fast passage of water molecules via the membrane. In pure water flux testing, the water flux of the membrane remained above 46.58 Lm-2h-1bar-1, while the salt rejection rate was relatively low.