M2 Membrane Research Articles

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.

Novel polyethersulfone-functionalized graphene oxide (PES-fGO) mixed matrix membranes for wastewater treatment

In this study, three routes of nucleophilic substitution of graphene oxide (GO) were compared for the fabrication of novel polyethersulfone-functionalized GO (PES-fGO) mixed matrix membranes. These routes were: crosslinking of GO with maleic acid containing nucleophilic dicarboxyl groups (M1); co-polymerization of GO with hyperbranched polyethyleneimine (HPEI) with excess amino group (M2); and nucleophilic modification of GO with naturally-derived chitosan containing amino and hydroxyl groups (M3). These membranes were then characterized and tested for the treatment of electrokinetically remediated wastewater. Membrane properties such as mechanical strength, morphology, chemical functionalities, hydrophilicity and pore structures were measured to assess the membranes in relation to their performance. M2 membrane displayed the least open and densest structure due to the abundance of nucleophilic amino groups on HPEI. The flexible NH chains increased the resistance of the active layer to water and contributed to the lowest water fluxes provided by M2 membrane. Regardless of viscous hindrance, intermolecular bonds with higher energies (CO in M1 and OH in M2) promoted thermodynamic instability which increased the pore sizes and water fluxes through M1 and M3. Therefore, the highest tensile strength and allowable load were exhibited by M2 membrane. The CONH linkages in M2 contributed to the highest overall pollutant removal efficiencies: 97.1% Fe2+, 95.3% Zn2+, 92.7% Cd2+, 99.9% Cr6+, 99.9% bacteria, and 98% chemical oxygen demand (COD) due to stronger repulsive electrostatic force and nano-sized membrane pores.

Observation of the Imidazole-Imidazolium Hydrogen Bonds Responsible for Selective Proton Conductance in the Influenza A M2 Channel.

The integral membrane M2 protein is a 97-residue membrane protein that assembles as a tetramer to conduct protons at a slow rate (102-103/s) when activated by low pH. The proton conductance mechanism has been extensively debated in the literature, but it is accepted that the proton conductance is facilitated by hydrogen bonds involving the His37 residues. However, the hydrogen bonding partnership remains unresolved. Here, we report on the measurement of 15N-15N J-couplings of 15N His37-labeled full length M2 (M2FL) protein from Influenza A virus embedded in synthetic liquid crystalline lipid bilayers using two-dimensional J-resolved NMR spectroscopy. We experimentally observed the hydrogen-bond mediated J-couplings between Nδ1 and Nε2 of adjacent His37 imidazole rings, providing direct evidence for the existence of various imidazolium-imidazole hydrogen-bonding geometries in the histidine tetrad at low pH, thus validating the proton conduction mechanism in the M2FL protein by which the proton is transferred through the breaking and reforming of the hydrogen bonds between pairs of His37 residues.

Self-cleaning properties of L-Histidine doped TiO2-CdS/PES nanocomposite membrane: Fabrication, characterization and performance

The polyethersulfone (PES) membrane incorporated with L-Histidine doped TiO2-CdS photocatalytic nanocomposite is fabricated to improve the membrane performance and its antifouling properties. The L-Histidine doped TiO2-CdS/PES nanofiltration membrane was characterized by scanning electron microscopy (SEM), contact angle and atomic force analysis (AFM) analyses. SEM images and contact angle results are demonstrated that membrane porosity and its hydrophilic properties increase with adding of L-Histidine doped TiO2-CdS photocatalytic nanocomposite. Moreover, AFM images of the modified membranes indicate favorable changes in surface roughness resulting in the improvement of antifouling properties. The pure water flux, flux recovery ratio (FRR) during filtration of milk powder and activated sludge suspension were also measured in a dead end cell. Increasing membrane permeability and FRR value approved its effective role of the added nanoparticles into the PES matrix. The M3 (0.5 wt% of NPs) membrane is selected as an optimal nanocomposite membrane which exhibits a much higher pure water flux (42.1 kg/m2 h) and FRR value (90 and 97% during filtration of milk powder and activated sludge suspension, respectively). The photocatalytic capability and antifouling properties of the M3 membrane as an optimum membrane were also investigated in a cross flow cell under continuous visible light irradiation. As a result, the high permeation flux (34.7 kg/m2 h), COD removal (100%) and FRR value (99%) was achieved during filtration of biologically treated palm oil mill effluent (POME) with COD concentration of 1000 mg/L at feed flow rate of 150 L/h and pressure of 5 bar. Effect of feed flow rate (50 and 150 L/h) and COD concentration (1000, 3000 and 5000 mg/L) on the membrane performance and its fouling resistance was also evaluated. Increasing feed concentration shows a negative effect on the membrane performance while feed flow rate increases separation performance and self-cleaning properties of the M3 membrane.

In situ immobilization of silver on polydopamine-coated composite membrane for enhanced antibacterial properties

In this work, the polyethersulfone (PES)-based membranes were prepared via phase inversion technique in the presence of polyvinylpyrrolidone (PVP) as a pore-forming agent. Polydopamine (PDA) coating followed by silver (Ag) immobilization was then carried out on the PES + PVP blend membrane to enhance the membrane wettability and antibacterial property, respectively. In total, four different membrane samples, namely pristine PES (M1), PES + PVP (M2), PDA/PES + PVP (M3) and Ag/PDA/PES + PVP (M4) were produced. The fabricated membranes were characterized with respect to physical morphology, contact angle, pure water permeability (PWP), humic acid (HA) and Escherichia coli (E. coli) rejection as well as antibacterial activity. The pristine PES membrane (M1) was reported to remove 77.81% HA and 96.4% E. coli. With the addition of PVP into the membrane matrix, the HA and E. coli rejection of M2 membrane was further improved to 79.94% and 99.33%, respectively. Upon PDA coating, the M3 membrane recorded much higher rejection rate (89.97% and 99.85%, respectively) owing to the formation of additional layer that reduced membrane pore size. It is interesting to note that complete elimination of E. coli was able to achieve by immobilizing Ag on the M4 membrane. This membrane also exhibited the greatest antibacterial activity and the highest HA rejection among all the fabricated membranes.

The The Effect of UVC Irradiation on the Structure and Swelling Properties of Chitosan Membranes Exposed to Magnetic Fields

Abstract – Research on the effect of UVC radiation exposure on the structure and swelling properties of chitosan membranes exposed to magnetic fields has been carried out. The membrane used is the 2% chitosan membrane that has been exposed to a magnetic field of 1.5 mT in a parallel direction for 2 hours at the time of its formation (formation reaction). Furthermore, the dry membrane obtained was cut to a certain size and irradiated by using UVC radiation for 5, 10, 15 and 30 minutes, each of which was given the names M1, M2, M3 and M4. A comparison is a 2% chitosan membrane with exposure to a magnetic field for 2 hours without exposure to UVC radiation, which is called the control membrane (M0). Characterizations conducted include thickness, swelling (water absorption) and FTIR spectrophotometer. FTIR analysis shows that the OH, NH, CH, C = O, CN, CO and COC functional groups observed on the M0 membrane as well as on the M1, M2, M3, and M4 membranes, with the peaks shifted to smaller or larger wavenumbers. The percentage of transmittance of these functional groups increases with increasing irradiation time from 5 to 15 minutes and decreases in 30 minutes irradiation.

Synthesis of ethanol perm-selective MFI zeolite membranes by binary structure directing agents

Good quality MFI zeolite membranes were prepared by altering a small amount of tetrapropylammonium (TPA+) with tetrabutylammonium (TBA+) in the synthesis solution. The effects of TBA+/Si ((TBA++TPA+)/Si ratio invariant) on the separation performance, hydrophobicity and compactness of MFI zeolite membranes were explored by pervaporation, water contact angle, scanning electron microscopy (SEM), X-ray diffraction (XRD), single-component gas permeation and permporosimetry. It was found that replacement of a small amount TPA+ with TBA+ could impair the hydrophobicity of membrane surface, but improve the membrane compactness verified by the ideal selectivity of N2/SF6 and permporosimetry. When TBA+/Si ratio increased to 0.02 from 0, the membrane separation factor was increased to 56 from 37 under crystallization time of 24 h, and 71 from 43 under crystallization time of 48 h. With increase of ethanol concentration in the feed from 1 to 50 wt%, the observed ethanol flux increased first and then decreased to that of single component pervaporation of ethanol, resulting in a peak value of the separation factor. The membrane M3 exhibited the highest separation factor of 79 with the flux of 1.40 kg m−2 h−1 for 3 wt% ethanol/water mixture while the highest separation factor of membrane M3-48 was 86 with the flux of 1.52 kg m−2 h−1 for 8 wt% ethanol/water mixture.