M2 Membrane Research Articles

Synthesize and characterization of polysulfone membrane for the separation of hydrogen sulfide from natural gas

The existence of Hydrogen Sulfide in natural gas (N.G) can lead to corrosion in equipment, global warming and so on. So, the separation of Hydrogen Sulfide from N.G is essential. In this study, the Polysulfone (PS) membrane was synthesized with Dimethylacetamide (DMAC) and Dimethylformamide (DMF) as solvent. The SEM (scanning electronic microscopy) images were used to compare prepared membranes by DMF and DMAC. An experimental setup was established and the effect of solvents, PS concentration, temperature and pressure were explored on the separation of H2S from N.G. The best temperature was achieved at 25°C. The results showed that the DMAC solvent was more appropriate than DMF and the amount of selectivity of this kind of membrane was reduced with an increase in temperature and pressure. In M3 membranes (20% of PS, DMAC solvent), which was the best membrane, the permeated amount was increased from 11800 to 490000 Barrer with an increase in pressure from 2.5 to 20 Barg, still the selectivity ratio of H2S to N.G was increased with increase in pressure from 2.5 to 5 Barg at first and then reduced with enhance in pressure until 20 Barg. The maximum selectivity ratio of H2S to N.G was 1.56 for M3 membranes at 25°C and 5 barg, at this condition, the permeated amount of H2S was 119000 Barrer.

How to Reduce the Emission of Microorganisms from a Biofilter Used to Treat Waste Gas from a Food Industry Plant

The aim of the study was to assess the bioaerosol removal efficiency by a semi-technical scale combined biofilter used to treat waste gas from a food industry plant. Two types of biofilter beds were tested: stumpwood chips and pine bark (CB) and stumpwood chips, pine bark and compost (CBC). Two types of membranes (covering the surface of the bed) were examined as the second stage of treatment: Pro Eko Tex UV (M1) and Pro Eko Tex UV 6 (M2). A conventional open biofilter (without membranes) was an emitter of microorganisms. There was no statistically significant difference between the number of bacteria emitted from CB or CBC beds, but fungal concentration was three times higher in gas treated by the CBC bed. The use of the membranes as the second stage of gas treatment significantly reduced the bacterial emission (74–78%) from the biofilter regardless of the bed and the membrane tested. The M1 membrane was also efficient in fungi removal from the treated gas by 80–97%. However, the M2 membrane could have been slowly colonized by fungi and have become an additional emitter of fungi in the system.

Re-use of waste cotton textile as an ultrafiltration membrane

Textile industry produces millions of tons of waste annually, which is predominantly incinerated or landfilled. Cotton textile comprises a quarter of total textile production, and although being renewable, its production is highly chemical- and water-intensive, rising the need for effective waste cotton textile recycling. This study presents an investigation whether it is possible to utilize waste cotton textile as a cellulose source for the fabrication of cellulose membranes. The effect of casting thickness and cellulose concentration on the prepared membranes’ performance was studied. Membranes cast from 2 wt% casting solutions exhibited the highest permeabilities of 1.11 and 3.09 m3/(m2·s·Pa) for 300 and 150 μm casting thickness, respectively, but poor adhesion stability and low retention. Membranes cast from solutions of higher concentrations (5, 6, and 7 wt%) resulted in membranes with more stable performance. The permeability values for 300 μm membranes were in the range of 0.27 – 0.39 m3/(m2·s·Pa) and for 150 μm 0.51 – 0.67 m3/(m2·s·Pa). The retention values of these six membranes were relatively close to each other, showing 80 – 92% retention of polyethylene glycol (PEG) 35 kDa. Three most promising membranes (5, 6, and 7 wt% cast at 150μm) were additionally characterized, showing negative zeta potential within −23 – −35 mV range at pH 7 and contact angles of very hydrophilic material (14 – 16°). Overall, the results showed that very hydrophilic ultrafiltration membranes having attractive permeability and retention properties can be made from textile waste. 1 m2 of cotton bed linen is enough to produce approximately 20 m2 of cellulose membrane.

An analysis on energy demands in airborne particulate matter filtration using hollow-fiber membranes

This work analyzes energy requirements for drawing the air through a hollow-fiber membrane (HFM) during air filtration. Polypropylene HFMs varying in inner fiber diameter (230 and 470μm) were used to separate the ASHRAE A2 fine test dust from a simulated particle laden environment. During the experiments, pressure drop, permeate velocity (air flowrate), fan frequency and power input were recorded. The obtained experimental data was analyzed using theoretical models relating pressure drop with power consumption necessary to overcome the membrane resistance. The results obtained for HFMs of different parameters (especially inner fiber diameter) were compared in terms of air flowrate and dust loading rate. Their influence on the energy consumption to operate the fan in the filtration process was then evaluated. The results have shown the smaller diameter HFMs have significantly higher energy consumption to operate the blower (about 180 Wh/m3) compared to larger diameter membrane (approx. 100 Wh/m3). This was despite higher surface area (0.95 m2) of lower diameter membrane compared to lower surface (0.43 m2) of HFMs with larger diameter. The general course of energy consumption during dust loading varied depending on the inner fiber diameter rather than on dust loading. This was obvious no matter of the dust loading rate (2, 4 and 6 g/hr), which seems to have negligible effect at the adopted experimental conditions a consumption of 113, 102 and 116 Wh/m3, respectively).

Hybrid desalination system of mechanical vapor recompression based on membrane distillation

The microporous PTFE membrane was used for membrane distillation (MD) experiment and presented ultra-high efficiency of desalination. A hybrid desalination system combining membrane distillation and mechanical vapor compression (MD+MVR) had been developed on the basis of the MD experiment. The system featured that the latent heat and part of sensible heat of vapor from the MVR were recovered to heat the MD process, and the heating process occurred in the same module as the MD process. Models were built according to the energy and mass conservation for the system description. Based on the simulation and experimental data, when the system was assigned a treatment capacity 1000 kg h-1 for 1% saline water and with corresponding 875 kg h-1 fresh water production, it would be stuffed with 75.24 m2 of PTFE membrane and expense only 3.31 kW of electrical power, under 353 K of feed temperature in membrane module and 26 kPa of compressor suction pressure. The compressor power requirement would trade off the heat transfer area with variation of the heat transfer temperature difference. The higher the salinity concentration in the residual concentrate after distillation was, the higher the compressor power, membrane area and heat exchanger area would be.

Fabrication and optimization of tunable pore size poly(ethylene glycol) modified poly(vinylidene-co-hexafluoropropylene) membranes in vacuum membrane distillation for desalination

• PEG modified PVDF-co-HFP membranes with tunable pore size for desalination for VMD. • Membranes characterized for morphology, hydrophobicity, stability, flux and rejection performance. • TOPSIS to select optimal membrane based on overall performance and characteristics. • 3D CFD modelling with excellent synergy between estimated and experimental data. • Optimized membrane - 19.72 LMH flux and >99.8% rejection in desalination (4% NaCl). We report poly(vinylidene-co-hexafluoropropylene) (PVDF-co-HFP) flat sheet membranes incorporated with poly(ethylene glycol) (PEG) of varied molecular weights and concentrations, was incorporated in PVDF-co-HFP matrix by solution blending to achieve fine control over membrane pore size, porosity and PSD, which are essential requirements for high-performance VMD desalination. Prepared membranes were characterized by surface morphology, porosity, pore size and distribution, hydrophobicity, thermal and dimensional stability. Membrane porosity and thus permeate flux was increased with the concentration of PEG in the membrane matrix. A technique for order preference by similarity to the ideal solution (TOPSIS) was used to predict the most suitable membrane for water desalination by VMD. Reported M3 membrane (20 wt% PVDF-co-HFP + 10 wt% PEG-400) showed superior performance (>99.8% salt rejection, and 19.72 l m -2 h −1 ) in comparison to other PVDF based flat sheet membranes reported in the literature. A three-dimensional comprehensive computational fluid dynamics (CFD) model is also presented to describe the vapour flux profile in the VMD process with reasonable accuracy. Membrane based on PVDF-co-HFP copolymer incorporated with PEG showed longevity up to more than 100 hrs and assessed as promising membrane material for VMD process because of interconnected pore structure and narrow pore distribution.

Ion Exchange Membrane “ABC” – A Key Material for Upgrading Process Industries

AbstractIon exchange membrane plays a crucial role in transforming and upgrading traditional chemical manufacturing procedures and boosting a multitude of new applications. Due to the strict regulations on wastewater discharge and increasing demands of renewable energy, anion exchange membrane (“A” membrane), bipolar membrane (“B” membrane) and cation exchange membrane (“C” membrane) have become a key material for upgrading various process industries. Herein, we summarized several novel synthetic routes for “ABC” membranes fabrication from the viewpoints of designing novel membrane synthetic routes, regulating the ionic transport channels, imparting dynamic transfer regions, introducing intrinsic micro‐porosity into the membrane and among others. The account includes a brief introduction to membrane structure designs and fabrications, emerging and industrial applications, and perspectives on ion exchange membranes. Who is the most influenced person in your academic career?My supervisor academician Binglin He.How do you get into the field of ion exchange membrane?I got in contact with ion exchange membranes during my postdoc research in Nankai University under the guidance of Prof. Binglin He. My supervisor is known as “father of China's ion exchange resin”. But in the synthesis of ion exchange resin, the resin pellets larger than 6 mm or smaller than 4 mm cannot be used and are directly discarded. Therefore, Prof. He asked me to explore how to convert them into membrane shape so as to reuse the wasted resin. Since then I entered the field of ion exchange membrane.In your opinion, what is the most promising ion exchange membrane in the next couple years?Alkaline stable anion‐exchange membranes that can be used for hydrogen production from electrolytic water splitting, fuel cells, and electrochemical ammonia synthesis, etc.Besides the fundamental research, why do you spend a lot time andenergy to industrialize the ion exchange membrane?Ion exchange membrane is relatively a narrow product in the field of separation membrane materials. Nowadays, there are tremendous demands of these kind of membranes due to the stricter regulations on wastewater disposal. However, the development of ion exchange membranes in China lags far behind that in other developed countries. As a scientist in this filed, I believe that I have the responsibility to promote the development and advancement of our domestic ion exchange membrane. For this reason, four licensed patents of us have been transferred for industrialization and more than 400000 m2 of membranes were used per year in various industries.What is the greatest honor for your academic achievement?My students are my greatest honor. I am proud of more and more students being graduated from my lab, who have played/will play important roles in making our country stronger.What's your hobbies?Walking, playing basketball and cards.

The mechanism of lncRNA‐CRNDE in regulating tumour‐associated macrophage M2 polarization and promoting tumour angiogenesis

M2 macrophages can promote liver cancer metastasis by promoting tumour angiogenesis; however, the mechanism underlying macrophage polarization has not been completely revealed. In this study, we mainly explored the mechanism underlying long non‐coding RNA‐CRNDE (lncRNA‐CRNDE) in regulating M2 macrophage polarization and promoting liver cancer angiogenesis. The expression of CRNDE was up‐regulated or down‐regulated in THP‐1 cells (CRNDE‐/‐‐THP‐1 cells and pcDNA3.1‐CRNDE‐THP‐1). THP‐1 cells were co‐cultured with liver cancer cell line H22, and M2 polarization was induced in THP‐1 by IL‐4/13 to simulate tumour‐induced macrophage polarization. As a result, after CRNDE overexpression, THP‐1 cell viability was up‐regulated, the expression of M2 membrane marker CD163 was up‐regulated, and the proportion of F4/80 + CD163+ cells was also up‐regulated. ELISA assay showed that the expression of M2 markers (including TGF‐β1 and IL‐10) and chemokines (including CCl22 and CCL22) was up‐regulated, and the expression of key signals (including STAT6, JAK‐1, p‐AKT1, and Arg‐1) was also up‐regulated, which were significantly different compared with the control group (Con). In addition, the intervention effect of CRNDE on THP‐1 was consistent between co‐culture with H22 cells and IL‐4/13 induction assay. The induced M2 THP‐1 cells were co‐cultured with HUVEC. As a result, THP‐1 cells with CRNDE overexpression can promote the migration and angiogenesis of HUVEC cells in vitro and simultaneously up‐regulate the expression of Notch1, Dll4 and VEGFR2, indicating that THP‐1 M2 polarization induced by CRNDE could further promote angiogenesis. The H22 cell tumour‐bearing mouse model was constructed, followed by injection of CRNDE anti‐oligosense nucleotides and overexpression plasmids to interfere CRNDE expression in tumour‐bearing tissues. Consequently, down‐regulation of CRNDE could down‐regulate tumour volume, simultaneously down‐regulate the expression of CD163 and CD31 in tissues, decrease the expression of key proteins (including JAK‐1, STAT‐6, p‐STAT6 and p‐AKT1), and down‐regulate the expression of key angiogenesis‐related proteins (including VEGF, Notch1, Dll4 and VEGFR2). In this study, we found that CENDE could indirectly regulate tumour angiogenesis by promoting M2 polarization of macrophages, which is also one of the mechanisms of microenvironmental immune regulation in liver cancer.

Improved anti-organic fouling of polyvinyl chloride-based heterogeneous anion-exchange membrane modified by hydrophilic additives

Organic fouling – which generally gives a more severe effect on anion-exchange membranes (AEMs) – leads to performance degradation of electro-membrane processes. In this work, polyvinyl chloride (PVC)-based AEM was prepared by a solution casting method. Three AEMs were modified by different hydrophilic additives, namely polyethylene glycol 400 (PEG400), polyethylene glycol 1000 (PEG1000), and ZnO nanoparticles (M2-M4 membranes). Then, the properties of these modified membranes were compared to the pristine membrane (M1 membrane). The effect of hydrophilic additives on the anti-organic fouling properties of modified membranes was investigated during a simple electrodialysis test of feed water containing humic substances. The results of chemical structure analysis show that the additives are successfully incorporated in the membrane matrix. The presence of the hydrophilic additive in the membrane matrix increases membrane conductivity. The highest increase in conductivity is obtained by the addition of PEG400 (up to 50 %). Meanwhile, water uptake, ion-exchange capacity, and water contact angle of the modified membranes are insignificantly changed. In addition, the additives can improve membrane resistance toward organic fouling. The introduction of additive can suppress the increasing rate of membrane areal resistance by ∼60 %.

Potentiometric Response of Solid-State Sensors Based on Ferric Phosphate for Iron(III) Determination.

A novel ion-selective electrode with membranes based on iron(III) phosphate and silver sulfide integrated into a completely new electrode body design has been developed for the determination of iron(III) cations. The best response characteristics with linear potential change were found in the iron(III) concentration range from 3.97 × 10−5 to 10−2 mol L−1. The detection limit was found to be 2.41 × 10−5 mol L−1 with a slope of −20.53 ± 0.63 and regression coefficient of 0.9925, while the quantification limit was 3.97 × 10−5 M. The potential change per concentration decade ranged from −13.59 ± 0.54 to −20.53 ± 1.56 for Electrode Body 1 (EB1) and from −17.28 ± 1.04 to −24 ± 1.87 for Electrode Body 2 (EB2), which is presented for the first time in this work. The prepared electrode has a long lifetime and the ability to detect changes in the concentration of iron cations within 20 s. Membrane M1 showed high recoveries in the determination of iron cations in iron(III) standard solutions (98.2–101.2%) as well as in two different pharmaceuticals (98.6–106.5%). This proves that this type of sensor is applicable in the determination of ferric cations in unknown samples, and the fact that all sensor parts are completely manufactured in our laboratory proves the simplicity of the method.

Polydopamine-Assisted Two-Dimensional Molybdenum Disulfide (MoS2)-Modified PES Tight Ultrafiltration Mixed-Matrix Membranes: Enhanced Dye Separation Performance.

Tight ultrafiltration (TUF) membranes with high performance have attracted more and more attention in the separation of organic molecules. To improve membrane performance, some methods such as interface polymerization have been applied. However, these approaches have complex operation procedures. In this study, a polydopamine (PDA) modified MoS2 (MoS2@PDA) blending polyethersulfone (PES) membrane with smaller pore size and excellent selectivity was fabricated by a simple phase inversion method. The molecular weight cut-off (MWCO) of as-prepared MoS2@PDA mixed matrix membranes (MMMs) changes, and the effective separation of dye molecules in MoS2@PDA MMMs with different concentrations were obtained. The addition amount of MoS2@PDA increased from 0 to 4.5 wt %, resulting in a series of membranes with the MWCO values of 7402.29, 7007.89, 5803.58, 5589.50, 6632.77, and 6664.55 Da. The MWCO of the membrane M3 (3.0 wt %) was the lowest, the pore size was defined as 2.62 nm, and the pure water flux was 42.0 L m−2 h−1 bar−1. The rejection of Chromotrope 2B (C2B), Reactive Blue 4 (RB4), and Janus Green B (JGB) in aqueous solution with different concentrations of dyes was better than that of unmodified membrane. The separation effect of M3 and M0 on JGB at different pH values was also investigated. The rejection rate of M3 to JGB was higher than M0 at different pH ranges from 3 to 11. The rejection of M3 was 98.17–99.88%. When pH was 11, the rejection of membranes decreased with the extension of separation time. Specifically, at 180 min, the rejection of M0 and M3 dropped to 77.59% and 88.61%, respectively. In addition, the membrane had a very low retention of salt ions, Nacl 1.58%, Na2SO4 10.52%, MgSO4 4.64%, and MgCl2 1.55%, reflecting the potential for separating salts and dyes of MoS2@PDA/PES MMMs.

Preparation of Multipurpose Polyvinylidene Fluoride Membranes via a Spray-Coating Strategy Using Waterborne Polymers.

As reported herein, the waterborne polymers poly(glycidyl methacrylate-co-poly(ethylene glycol) methyl ether methacrylate) P(GMA-co-mPEGMA) and polyethyleneimine (PEI) were used to prepare multipurpose polyvinylidene fluoride (PVDF) membranes via a direct spray-coating method. P(GMA-co-mPEGMA) and PEI were alternately sprayed onto the PVDF membrane to yield stable cross-linked copolymer coatings. The successful coating of polymers onto the membrane surface was verified by scanning electron microscopy, attenuated total reflectance-Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy characterization. The coated membrane exhibited oil rejection rates that exceeded 99.0% for oil water mixture separation and 98.0% for oil/water emulsion separation. The flux recovery ratio reached 96.7% after bovine serum albumin filtration and washing with water. The removal efficiencies of the coated membrane M3 for Congo red, methyl orange, methylene blue, and crystal violet, Pb(II), Cu(II), and Cd(II) were 82.4, 83.9, 6.3, 26.8, 90.6, 91.3, and 86.2%, respectively. Thus, it can be used for the removal of dyes and heavy metal ions from wastewater. The antibacterial activities of the coated membranes were also confirmed by the inhibition zone tests and confocal laser scanning microscopy analysis. In addition, the cross-linking strategy provides the coated membranes with excellent durability and repeatability. More importantly, the use of water as the solvent can ensure that the application of these membrane coatings proceeds via a very safe and environmentally friendly coating process.

IMPREGNATION OF ORAL MUCOSA OVER IMPACTED TEETH BY SUBPOPULATIONS OF MACROPHAGES M1 AND M2

The aim: Of the study is to research quantitative parameters of mucous membrane macrophages populations M1 (CD68+) and M2 (CD163+) over vestibularly and palatally impacted teeth. Materials and methods: A group of 21 people aged from 10 to 16 years was formed to conduct the research. Clinical situation according to diagnostic criteria was identical in all the patients. The group was divided into two groups - control and experimental, which in their turn were fragmented into two subgroups. Immunohistochemical studies of mucosal biopsies were performed in accordance with the recommendations for selection. Results: Study of ratio of CD68+/CD163+ cells revealed imbalance in individuals with vestibularly impacted teeth due to higher infiltration density of CD163+ (p<0,05), compared to CD68+ of control group. In individuals with palatally impacted teeth, ratio of CD68+/CD163+ increased 3,6 times, as well as compared with control group, but due increased infiltration density of CD68+. Conclusions: In the epithelium of oral mucosa located over impacted teeth, both on vestibular and palatal surface, number of CD 68+ and CD163+ cells had no significant differences compared to control group. In biopsies of the lamina propria of mucosa over vestibularly impacted teeth, the ratio M1/M2=0,91±0,11 (p<0,05) decreases, with predominance of macrophages CD163+ subpopulation activity, and over palatally impacted teeth balance of M1/ M2 macrophages elevated (M1/M2= 2,10 ± 0,32, p<0,05), due to increased infiltration density of CD68+.

Improved anaerobic digestion of swine manure by simultaneous ammonia recovery using gas-permeable membranes

In feedstocks containing high ammonia (NH3) concentration, removal of the NH3 during the anaerobic digestion (AD) process can improve AD process performance. In the present study, the effect of NH3 removal using gas-permeable membrane (GPM) technology on AD process performance and biogas production was investigated using swine manure feedstock. Batch and semi-continuous AD experiments were carried out under mesophilic conditions. In the reactor with NH3 recovery, total ammonia nitrogen (TAN) concentration was reduced 28% in batch experiments and 23% on average in the semicontinuous experiment compared with the reactor without NH3 recovery. Free ammonia (FA) concentrations were also decreased by 23% and 4% on average in batch and semicontinuous experiments, respectively. These reductions in TAN and FA by GPM system positively impacted both the quality and quantity of the biogas produced by AD of swine manure. Specifically, the specific methane yield increased 9% in the batch experiment and 17% on average in the semicontinuous experiment. Furthermore, higher percentages of methane in biogas were obtained during AD retrofitted with GPM system, 24% increase in the batch experiment and 11% on average in the semicontinuous experiment (range 8.3-13.6%). Simultaneously, a uniform TAN recovery rate of 6.7 g N TAN per m2 of membrane and per day was obtained for the 205 days of semicontinuous operation; ammonia nitrogen was recovered in the form of ammonium sulphate solution. Therefore, the AD-GPM configuration produces beneficial results on biogas quantity and quality while recovering ammonia nitrogen in form of ammonium sulphate.

Magnetic rod induced asymmetric membrane: Effect of iron oxide composition to phenol removal by adsorption

Particle migration within membranes with different iron oxide compositions was prepared by traditional casting under direct exposure to a magnetic rod. Membrane with 30 wt% of iron oxide (M30) has shown a high concentration of Fe element within its thin layer compared to other membranes with lower iron oxide content. The high Fe element in the M30 thin layer has contributed to its porous structure (58.9% porosity), the most porous among the membranes. Hence, it explained the high water flux of the M30 membrane at 75.4 L/m2.h, while the pristine N0 membrane only managed 20.1 L/m2.h. Due to particle migration towards the membrane surface, all magnetically induce membrane were able to obtain a contact angle below 70⁰, characteristic of a hydrophilic surface. Moreover, due to the accumulation of iron oxide as a result of magnetic casting, the M3 membrane was able to remove 14.1% of phenol with a sieving coefficient of 0.86. To conclude, magnetic induce casting has the capability of orienting and migrating the iron oxide within the membrane matrix without the need for an additional chemical or complicated procedure.

Preparation of novel high permeability and antifouling polysulfone-vanillin membrane

A novel high-performance nanofiltration membrane was fabricated by a simple and scalable route involving in situ cross-linking of hydrophilic, cheap, and environmentally friendly vanillin as antifouling agent with polysulfone (PSf) for salt rejection performance. Vanillin acts as a porogen, which induces a negative surface charge on the membrane surface due to the presence of polar functional groups like alcohol and aldehyde. The surface properties, including charge, morphology, and hydrophilicity, were investigated in detail using analytical instruments. The nanofiltration performance of the fabricated PSf-vanillin membranes was dependent on the percentage of vanillin added in the casting solution. The PSf-vanillin membrane antifouling tests were evaluated using 200 mg/L bovine serum albumin (BSA), and results showed 99% rejection with 88.55% flux recovery ratio. Performance studies were compared with commercially available TRISEP® UA60 nanofiltration membrane. PSf-vanillin membrane M2 showed higher MgSO4 (87.49%), NaCl (25.78%) rejection with excellent antifouling properties compared to commercial UA60 membrane. It is believed that charged membranes are the building blocks for the development of future generation desalination membranes possessing high permeability and selectivity index. The developed membranes have potential niche application in the pre-treatment of feed solution.

Multilayer UF membrane assisted by photocatalytic NZVI@TiO2 nanoparticle for removal and reduction of hexavalent chromium

Photocatalytic polyethersulfone (PES) membranes with a high degree of hexavalent chromium (Cr(VI)) removal, hydrophilicity, water permeability and antifouling properties were fabricated via layer by layer assembly (LBL) technology. The novel PES ultrafiltration (UF) membranes were developed with different bilayers of chitosan (CHI)-alginate (ALG) and nano zero-valent iron@TiO2 (NZVI@TiO2) photocatalytic nanoparticles. The morphology, chemical structure and wettability of synthesized nanoparticles and fabricated membranes were characterized by FESEM, AFM, EDX, XRD, FTIR and contact angle analyzer. The PES-UF membrane containing four CHI layers and one layer of NZVI@TiO2 photocatalytic nanoparticles (M5) has shown maximum efficiency for Cr(VI) removal from permeate and retentate streams compared to the other membranes, 100 %, 98.1 % and 95.5 % Cr(VI) removal in permeate and 76.4 %, 46.7 % and 34.4 % Cr(VI) removal in retentate were obtained for 5, 15 and 30 ppm feed concentration, respectively. The modifications of the neat PES led to high hydrophilicity and desirable antifouling properties. The water flux of neat PES, M1, M2, M3, M4 and M5 membrane were obtained 161, 152, 186, 147, 178 and 170 L/m2.h, respectively. According to results, the membranes containing NZVI@TiO2 photocatalytic nanoparticles have shown high water flux. Moreover, M5 membrane has exhibited 68 % flux recovery whereas neat PES membrane has shown 43 %. For 5 ppm feed concentration, the Cr(VI) removal decreased from an about 100 % to 71 ± 2%, 48 ± 2% and 42 ± 1% with increasing pH from 3 to 5, 7 and 10, respectively.

Cholesterol Alters the Orientation and Activity of the Influenza Virus M2 Amphipathic Helix in the Membrane.

The influenza virus M2 amphipathic helix (M2AH) alters membrane curvature in a cholesterol-dependent manner, mediating viral membrane scission during influenza virus budding. Here, we have investigated the biophysical effects of cholesterol on the ability of an M2AH peptide to manipulate membrane properties. We see that the ability of the M2AH to interact with membranes and form an α-helix is independent of membrane cholesterol concentration; however, cholesterol affects the angle of the M2AH peptide within the membrane. This change in membrane orientation affects the ability of the M2AH to alter lipid order. In low-cholesterol membranes, the M2AH is inserted near the level of the lipid head groups, increasing lipid order, which may contribute to generation of the membrane curvature. As the cholesterol content increases, the M2AH insertion becomes flatter and slightly deeper in the membrane below the lipid headgroups, where the polar face can continue to interact with the headgroups while the hydrophobic face binds cholesterol. This changed orientation minimizes lipid packing defects and lipid order changes, likely reducing the generation of membrane curvature. Thus, cholesterol regulates M2 membrane scission by precisely modulating M2AH positioning within the membrane. This has implications for the understanding of many of amphipathic-helix-driven cellular budding processes that occur in specific lipid environments.

Improved permeation, separation and antifouling performance of customized polyacrylonitrile ultrafiltration membranes

Tailored polyacrylonitrile (PAN) ultrafiltration (UF) membranes are fabricated with Pluronic-F127 and polyethylene glycol phosphate decorated calcium carbonate (PGP-CaCO3) additives with the aim of high water permeation, macromolecular rejection and antifouling properties. The nanoscale CaCO3 synthesis is carried out via a single step carbonization route using PGP as a hydrophilic modifier to introduce hydroxyl groups onto its surface. The topographies of the nanoparticles are investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). PAN/PGP-CaCO3 mixed matrix membranes (MMMs) are fabricated via phase inversion method and examined by attenuated total reflectance-Fourier infra-red spectroscopy (ATR-FTIR), mechanical stability, thermo-gravimetric analysis (TGA) and scanning electron microscopy (SEM) to explore the changes in membrane properties due to the well-dispersed PGP-CaCO3 in the PAN membrane matrix. The UF performance of the membranes is investigated in terms of pure water flux, macromolecular rejection and antifouling property. The fouling resistance of membranes is assessed using bovine serum albumin (BSA) and humic acid (HA) as model foulants. The membrane loaded with 0.75wt.% (M3) of PGP-CaCO3 manifested increased wettability with reduced surface free energy leading to a higher pure water flux of 366L/m2h. M3 also displayed a rejection of 93.9% for BSA and 93.2% for HA. The success of the modification can be confirmed as the membrane M3 exhibited lower flux decline and displayed a flux recovery ratio of 90.98% during HA filtration. The results demonstrated the potential use of PAN/PGP-CaCO3 membranes in water treatment.

Simulation of S-Entropy Production during the Transport of Non-Electrolyte Solutions in the Double-Membrane System.

Using the classical Kedem–Katchalsky’ membrane transport theory, a mathematical model was developed and the original concentration volume flux (Jv), solute flux (Js) characteristics, and S-entropy production by Jv, and by Js in a double-membrane system were simulated. In this system, M1 and Mr membranes separated the l, m, and r compartments containing homogeneous solutions of one non-electrolytic substance. The compartment m consists of the infinitesimal layer of solution and its volume fulfills the condition Vm → 0. The volume of compartments l and r fulfills the condition Vl = Vr → ∞. At the initial moment, the concentrations of the solution in the cell satisfy the condition Cl < Cm < Cr. Based on this model, for fixed values of transport parameters of membranes (i.e., the reflection (σl, σr), hydraulic permeability (Lpl, Lpr), and solute permeability (ωl, ωr) coefficients), the original dependencies Cm = f(Cl − Cr), Jv = f(Cl − Cr), Js = f(Cl − Cr), = f(Cl − Cr), = f(Cl − Cr), Rv = f(Cl − Cr), and Rs = f(Cl − Cr) were calculated. Each of the obtained features was specially arranged as a pair of parabola, hyperbola, or other complex curves.