Antibacterial ultrafiltration membrane with silver nanoparticle impregnation by interfacial polymerization for ballast water

Interfacial polymerization technology was employed to immobilize silver (Ag) nanoparticles on the surface of commercial polyethersulfone (PES) membrane to develop antibacterial and antifouling ultrafiltration membrane. Ag nanoparticles were prepared from the reduction of silver nitrate (AgNO₃) by sodium borohydride in the presence of polyethyleneimine (PEI) as the stabilizer. The encapsulated Ag nanoparticles in the PEI solution were embedded into the PEI membrane when trimesoyl chloride solution was used to crosslink the PEI solution with the PES membrane, forming Ag-polyamide (PA) networks through the interfacial polymerization reaction. Experimental results showed that the membrane prepared with 50 mmol/L of AgNO₃ and 20 mmol/L of PEI had the optimized antibacterial effect against Escherichia coli. Bacterial concentration and species were also investigated. Exiguobacterium aestuarii and Staphylococcus aureus which are gram-positive bacteria, needed significantly more time for the Ag-PA/PES membrane to kill the bacteria completely when compared to E.coli and Vibrio coralliilyticus which are gram-negative bacteria. This study showed that Ag nanoparticles impregnated in membrane surfaces were 100% effective in killing various types of marine bacteria and bacteria in the seawater collected off Sentosa Island in Singapore. These membranes exhibit excellent antibacterial and antifouling properties which can be used to kill bacteria in ballast water and seawater.     

聚醚砜/纤维素晶体共混膜材料及其超滤性能

聚醚砜与纤维素晶体等共混成铸膜液,采用浸没沉淀相转化法制备聚醚砜/纤维素晶体共混膜材料.通过超滤装置检测复合膜的水通量、截留率、平均孔径、孔隙率、抗污染性等超滤性能,从而讨论了纤维素晶体含量对共混膜超滤性能的影响.采用抗张测试机、热重分析仪(TGA)、原子力显微镜(AFM)对共混膜的力学性能、热稳定性能、形貌结构进行表征.结果表明,随着纤维素晶体的含量的增加,共混膜的纯水通量先升高后有所降低,截留率均保持在91%～95%,抗张强度、断裂伸长率先增大后有所下降,抗污染性较纯聚醚砜膜显著提高.当纤维素晶体质量分数为1%时,纯水通量达到最大为813.3L·m-2·h-1,孔隙率为88.8%,平均孔径达为70.9nm,抗张强度为7.25MPa,断裂伸长率为11.6%,平均污染度FR值为22.0%,衰减系数m值为35.8%.共混膜具有由纤维素晶体、聚醚砜热降解分别引起的两个失重阶段.共混膜为典型非对称膜结构,表皮层较为致密,多孔支撑层孔径较大.     

Separation of nitrogen and oxygen gases by polymeric membrane embedded with magnetic nano‐particle

Asymmetric polyethersulfone (PES) micro‐porous flat sheet membranes were prepared by the phase inversion method (PIM) and used as the support. PES‐PDMS composite membranes were fabricated with coating polydimethylsiloxane on the surface of PES membrane. The FluidMAG‐PAD was coated on PES and PES‐PDMS membrane to prepare super‐paramagnetic membranes for separation of oxygen from nitrogen. Permeance and O₂/N₂ selectivity were evaluated in the absence or presence of external magnetic field. In the absence of external magnetic field, the super‐paramagnetic polymer provides larger surface area leading to extended sites for oxygen adsorption. In the presence of magnetic field, the super‐paramagnetic particles obtained magnetic property leading to a pronounced interaction with oxygen resulting in elevated selectivity and permeability. Copyright © 2011 John Wiley & Sons, Ltd.     

Preparation and characterization of nanostructured thin films of Au and Ag nanoparticles synthesized by ascorbic acid on modified glass surface

Immobilization of Ag and Au nanoparticles (NPs) synthesized by ascorbic acid on chemically modified glass surface has been studied. 3‐[2‐(2‐Aminoethylamino)ethylamino]propyl‐trimethoxysilane (AMPTS), N‐(2‐aminoethyl)‐3‐aminopropyltrimethoxysilan, and 3‐trimethoxysilyl‐1‐propanethiol (MSPT) were used as surface modifying agents. To improve immobilization efficiency, the ammonia solution has been used along with the silane reagents, which assisted to adsorb the metal NPs on glass surface. It was found that AMPTS and MSPT have considerable effect on deposition of Ag and AuNPs on glass substrate. The fabricated thin films were characterized by using UV‐Vis spectroscopy, atomic force microscopy, energy‐dispersive X‐ray spectroscopy and subjected to antimicrobial resistance test. The UV–Vis spectra show a distinctive plasmon resonance absorbance peak for thin films of Au and AgNPs prepared with MSPT and AMPTS, respectively. Atomic force microscopy images indicate that formation of Au and AgNPs with spherical morphology after immobilization on the glass substrate and also the dimensions of NPs on the surface appear larger than those observed in the parent colloidal solution. Energy‐dispersive X‐ray spectroscopy measurements confirmed the presence of silver and gold on the modified glass surface, and elemental composition was measured. The Au and AgNPs thin films show antibacterial activity against gram negative (Escherichia coli) and gram positive (Staphylococcus aureus) bacteria in comparison with a blank sample. Copyright © 2015 John Wiley & Sons, Ltd.     

Protein-adsorption-resistance and permeation property of polyethersulfone and soybean phosphatidylcholine blend ultrafiltration membranes

Novel ultrafiltration membranes were prepared by simple blending of polyethersulfone (PES) and soybean phosphatidylcholine (SPC). X-ray photoelectron spectroscopy (XPS) and water contact angle measurements indicated SPC enrichment at the membrane surfaces. The immobilization and arrangement of PC groups at surfaces rendered the membranes more hydrophilic. BSA adsorption amount decreased from 56.2 μg/cm² for SPC-free PES membrane to 2.4 μg/cm² for PES/SPC blend membrane. The fouling-resistant property of the blend membranes was improved considerably with an increase of SPC content while the pure water permeation flux decreased remarkably. Using PEG/PVP mixture instead of PEG as pore-forming agent increased pure water flux of PES/SPC blend membrane to some extent.     

Improved microfiltration and bacteria removal performance of polyethersulfone membranes prepared by modified vapor‐induced phase separation

Polyethersulfone (PES) microfiltration membranes were fabricated by a combined vapor‐induced phase separation and wet phase separation method. The effect of different non‐solvent additives in casting solution, ie, acetone, diethylene glycol, and triethylene glycol (TEG) was investigated on the membrane morphology and performance. Scanning electron microscopy images showed that the membrane containing TEG additive had a skinless symmetric structure with well interconnected pores. The permeability of the PES/PVP/TEG membranes increased by decreasing PES and TEG and increasing PVP concentration. Bacteria removal performance of the prepared membranes was investigated by the filtration of E. coli suspension. The membrane made from casting solution containing 15 wt.% PES, 16 wt.% PVP, and 20wt.% TEG showed a pure water flux of ~ 5370 L/m² h at low transmembrane pressure of 10 psi and 100% bacteria removal efficiency. The results of in vitro cytotoxicity test and cell viability assay showed non‐toxic nature of the prepared membranes.     

Synthesis and characterization of asymmetric polyethersulfone membranes: effects of concentration and polarity of nonsolvent additives on morphology and performance of the membranes

In this study, effects of methanol, ethanol and 1‐propanol as variable nonsolvent additives (NSAs) on the morphology and performance of flat sheet asymmetric polyethersulfone (PES) membranes were investigated. The membranes were prepared from PES/Polyvinylpyrrolidone (PVP)/N‐methyl‐2‐pyrrolidone (NMP) system via phase inversion. The obtained results indicate that with the addition of NSAs to the casting solution, the membrane morphology changes slowly from macrovoids to an asymmetric structure with finger‐like pores. By increasing the NSAs concentrations in the casting solution and decreasing their polarities, the membrane structure changes from finger‐like pores to sponge. The AFM and SEM images reveal that addition of NSA to the casting solution decreases the pore size of the prepared membranes and reduces the pure water flux and BSA solution flux, while increasing the protein rejection. Surface analysis of the membranes showed that mean pore size and surface porosity of the prepared membranes with NSAs in the casting solution are smaller compared with those of the membrane prepared with no NSA. Pure water flux and BSA solution flux through the membranes decrease and BSA rejection increases with increase in the concentration of NSAs and decrease in their polarity. Finally, it can be concluded that the T_g values of the PES membranes increase by addition of NSAs to the casting solution. Copyright © 2009 John Wiley & Sons, Ltd.     

Preparation and characterization of asymmetric polyethersulfone (PES) membranes

Flat‐sheet asymmetric polyethersulfone (PES) membranes were prepared from polyethersulfone (PES)/ polyethylene glycol (PEG)/ N‐methyl‐2‐pyrrolidone (NMP) system via phase inversion induced by immersion precipitation in water coagulation bath. Effects of propionic acid (PA) as a non‐solvent additive (NSA) on morphology and performance of the membranes prepared from PES/PEG 6000/NMP system in water coagulation bath were investigated. The cross section morphology of the membranes was studied by scanning electron microscopy (SEM). In addition, performance of the membranes was studied by water content measurements and separation experiments using pure water and human serum albumin (HSA) protein solution as feeds. According to SEM analysis, it was found out that the NSA has a significant influence on the structure of the skin layer and the sublayer. The obtained results indicated that addition of PA to the casting solution decreases permeation flux of the prepared membranes. Copyright © 2009 John Wiley & Sons, Ltd.     

Enhanced antifouling and anticoagulant properties of grafted biomolecule polyethersulfone membranes

Polyethersulfone (PES) has been widely used in membrane technology and used to purify water in water treatments application or as a dialyzer to purify blood in hemodialysis. In this work, PES was chemically modified by separately grafting two biomolecules, 4‐aminobenzenesulfonamide (ABS), and 4‐amino‐N‐(5‐methylisoxazol‐3‐yl)benzenesulfonamide (AMBS), on PES backbone, and these modified membranes were blended to unmodified PES, in 1:1 ratio, in order to obtain PES‐b‐PES‐ABS and PES‐b‐PES‐AMBS membranes. The first aim of this study is to measure the anticoagulant properties of the modified membrane by measuring the activated partial thromboplastin time (APTT) and prothrombin time (PT). The second aim of the study is to evaluate the antifouling properties of the modified PES membranes by examining its antimicrobial activity against two Gram‐negative bacteria, which are Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli); two Gram‐positive bacteria, which are Bacillus subtilis (B. subtilis) and Staphylococcus aureus (S. aureus); and a fungus, which is Candida albicans (C. albicans). The results showed that grafting of ABS and AMBS improved overall the hydrophilicity properties of the modified PES membranes. PES‐b‐PES‐ABS membranes showed better anticoagulant properties with 13 seconds for PT and 38 seconds for APPT, in comparison with the control sample (pure plasma), which showed 12 seconds for PT and 30 seconds for APPT. For antimicrobial tests, both PES‐b‐PES‐ABS and PES‐b‐PES‐AMBS membranes did not show any antibacterial activity, but when zinc oxide (ZnO) nanoparticles were added to the modified PES membranes in concentrations between 3% to 5% w/w, PES‐b‐PES‐ABS‐ZnO (M‐4 and M‐5), and PES‐b‐PES‐AMBS‐ZnO (M‐8 and M‐9) nanocomposite membranes showed antibacterial activity against P. aeruginosa and S. aureus.     

Preparation and characterization of TiO2/Pebax/(PSf‐PES) thin film nanocomposite membrane for humic acid removal from water

New thin film composite (TFC) membrane was prepared via coating of Pebax on PSf‐PES blend membrane as support, and its application in wastewater treatment was investigated. To modify this membrane, hydrophilic TiO₂ nanoparticles were coated on its surface at different loadings via dip coating technique. The as‐prepared membrane was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy (SEM), field emission SEM, and contact angle analysis. The Fourier transform infrared spectroscopy analysis and surface SEM images indicated that TiO₂ was successfully coated on the membrane surface. In addition, the results stated that the hydrophilicity and roughness of membrane surface increased by addition of TiO₂ nanoparticles. Performance of TFC and modified TFC membranes was evaluated through humic acid removal from aqueous solution. Maximum permeate flux and humic acid rejection were obtained at 0.03 and 0.01 wt% TiO₂ loadings, respectively. Rejection was enhanced from 96.38% to 98.92% by the increase of feed concentration from 10 to 30 ppm. Additionally, membrane antifouling parameters at different pressures and feed concentration were determined. The results indicated that surface modification of membranes could be an effective method for improvement of membrane antifouling property.     

Silver nanoparticles immobilized on thin film composite polyamide membrane: characterization,nanofiltration, antifouling properties

Microbial biofouling is one of the major obstacles for reaching the ultimate goal of realizing a high permeability over a prolonged period of nanofiltration operation. In this study, the hybrid nanocomposite membranes consisting of silver (Ag) nanoparticles with antibiofouling capability on microorganism and polyamide (PA) were prepared by in situ interfacial polymerization and characterized by X‐ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). The hybrid membranes were shown to possess the dramatic antibiofouling effect on Pseudomonas. In addition, Ag nanocomposite membranes had little influence on the performances of the membrane such as on water flux and salt rejection. SEM analysis results showed that all Pseudomonas were dead on the PA/Ag nanocomposite membrane, indicating the effectiveness of silver nanoparticles. This investigation offers a strong potential for possible use as a new type of antibiofouling membrane. Copyright © 2007 John Wiley & Sons, Ltd.     

Oxidative stress induced antimicrobial efficacy of chitosan and silver nanoparticles coated Gutta-percha for endodontic applications

Root canal treatment is the most effective treatment for irreversible pulpal damage. However, it suffers the risk of failure due to micro-leakage at the Gutta-percha-sealer-tooth interface. Concerning the issue, it is important to enhance the antimicrobial properties of Gutta-percha. The current study describes a novel coating of the Gutta-percha with chitosan and silver nanoparticles to increase their antimicrobial efficacy. They were coated with chitosan and silver nanoparticles with concentrations of 1%, 2% using chemical methodology. Coated Gutta-percha were evaluated for their antimicrobial efficacy against E. faecalis, which is frequently isolated microorganism in failed endodontic cases using standard microbiological methods like growth curve analysis. Detailed analysis of the antimicrobial activity was performed by live-dead analysis with the help of flow cytometry and fluorescent microscopy. Although, the experimental analysis showed concentration-dependent antibacterial activity by both chitosan and silver NP coated Gutta-percha, the silver NP coating exhibited higher antibacterial activity compared to the Gutta percha coated with chitosan nanoparticles. Mechanistic evaluation unveiled the cause of antibacterial activates due to action of induced oxidative stress and membrane damage to the bacteria by coated nanoparticles. The information will be useful for the endodontist to have an alternative filling material with higher antibacterial potency for higher success rate of root canal therapies in clinical procedures.     

Preparation and performance evaluation of carboxylic acid containing polyamide incorporated microporous ultrafiltration PES membranes

Improved ultrafiltration membranes were prepared by the phase inversion technique via immersion precipitation of synthesized carboxylic acid containing polyamide (CPA) and polyethersulfone (PES) in dimethylacetamide. The CPA was synthesized and characterized by Fourier transform infrared (FTIR), nuclear magnetic resonance, thermogravimetric analysis, and differential scanning calorimetry analyses. Next, the influence of CPA adding and its different concentrations on the performances and membrane structure were investigated. The obtained membranes were characterized by means of FTIR in the attenuated total reflection mode, scanning electron microscopy, and contact angle. The membrane performance studies revealed that the presence of CPA in the membrane structure increased water permeability while reducing protein fouling. It turned out that the PES/CPA membranes had better porosity, more hydrophilic surface, and more vertically finger‐like pores in comparison with the bare PES membrane. When the CPA concentration in the blending solution reached 1 wt%, the water permeability increased from 7.3 to 153.6 L/m² h¹. The attenuated total reflection‐FTIR analysis confirmed that CPA was captured in the membrane matrix.     

One‐Step Preparation of Antimicrobial Polyrhodanine Nanotubes with Silver Nanoparticles

A simple synthetic method has been developed for the fabrication of antimicrobial polyrhodanine nanotubes with silver nanoparticles. Rhodanine monomer first forms one‐dimensional complexes with silver ions due to coordinative interactions and consecutively reduces the silver ions during chemical‐oxidation polymerization. The polymerization procedure is analyzed by transmission electron microscopy and scanning electron microscopy in situ. The synthesized silver nanoparticles/polyrhodanine nanotubes are applied as an antimicrobial agent against Gram‐negative bacteria, E. coli and Gram‐positive bacteria, S. aureus. The antimicrobial tests demonstrate that the silver/polyrhodanine nanotubes have superior antimicrobial properties to silver nanoparticles and rhodanine monomer.

     

Green synthesis and characterization of silver nanoparticles by Allium cepa L. to produce silver nano‐coated fabric and their antimicrobial evaluation

This research work was proposed to study the antimicrobial activity of the silver nanocoated fabric with the purpose of producing good dressing and clothing material. We synthesized simple, ecofriendly, cost‐effective and sustainable silver nanoparticles by using the aqueous extract of Allium cepa L. Here, A. cepa L. acts as a good reducing and capping agent that produced stable silver nanoparticles having particle size of range 36 ± 1 to 98 ± 2 nm, Poly dispersiblity index 0.234 ± 0.61 to 1.023 ± 0.33 and Zeta potential ‐12 ± 1.5 mV to ‐26 ± 1.2 mV. The effect of temperature and extract volume used was considered for optimization of synthetic procedure. The nanocoated fabric was characterized for morphological study, size (using transmission electron microscopy (TEM) and field emission scanning electron microscopy (FE‐SEM) and zeta‐potential (Zeta Potentiometer). The presence of functional groups were observed by using attenuated total reflection‐Fourier transform infrared (ATR‐FTIR) and Raman spectroscopy. The crystallinity and structural property of the synthesized silver nanoparticles were studied in terms of Powder X‐ray diffraction (PXRD). An IC₅₀ value and zone of inhibition was studied which demonstrate that the silver nanocoated fabric have an excellent antibacterial property against Gram‐negative (Escherichia coli) and Gram‐positive (Staphylococcus aureus) bacteria. Further nanocoated fabric material was washed (with function of time 0, 10, 25, and 50 laundry cycles) and still retained their anti‐bacterial activity towards both strain. Initially there was 52 μg/ml of silver nanoparticles on the cotton fabric but after 50 laundry cycle in 500 ml of distilled water the fabric showed 92% efficiency against gram positive and 90% efficacy toward gram negative bacteria. It was found that 4.16 μg/ml nano particles leached in case of S. Aureus and 5.2 μg/mL silver nanoparticles leached in case of E. coli. Nanocoated fabric material synthesized using green synthesis was found to be economical with good resistance to washing.     

A green approach to prepare Ag NPs loaded IC/PVA polymeric film for antimicrobial applications

In this study, glyoxal-cross-linked Iota carrageenan (IC) /poly(vinyl alcohol) PVA films were prepared and loaded with silver nanoparticles via a green approach, consisting of sweet lime juice induced in-situ reduction of Ag(I) ions to nano silver within the film matrix. The formation of silver nanoparticles was confirmed using UV–visible spectrophotometry. The Ag NPs-loaded films were also characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR). The dynamic water uptake data were interpreted by the ‘Power functional model’. The films showed fair antimicrobial action against bacteria E. Coli.     

Polyethersulfone/polyacrylonitrile blend ultrafiltration membranes with different molecular weight of polyethylene glycol: preparation,morphology and antifouling properties

Asymmetric ultrafiltration (UF) membranes were prepared from blends of polyethersulfone (PES)/polyacrylonitrile (PAN) via phase inversion method induced by immersion precipitation. Polyethylene glycol (PEG) with four different molecular weights was used as pore former and hydrophilic polymeric additive. N,N‐dimethylformamide (DMF) and water were used as solvent and coagulant (nonsolvent), respectively. The effects of different proportion of PES/PAN and molecular weight of PEG on morphology and performance of the prepared membranes were investigated. Performance of the membranes was evaluated using UF experiments of pure water and buffered bovine serum albumin (BSA) solution as feed. The contact angle measurements indicated that the hydrophilicities of PES/PAN membrane increase by increasing the PAN concentration in the casting solution. However, performance of the membranes improves by increasing the PAN concentration in the casting solution up to 20% and then decreases with further addition of PAN. It was found out that the rejection of BSA decreases with increasing the PAN concentration in the casting solution. Furthermore, it was found that the performance of the membranes increases by increasing the molecular weight of PEG up to 1500 Da and then decreases with the higher molecular weights. The morphology of the prepared membranes was studied by scanning electron microscopy. Copyright © 2011 John Wiley & Sons, Ltd.     

In situ Synthesis of Oil Based Polymer Composites Containing Silver Nanoparticles

Using electron transfer reaction and free radical polymerization processes a series of triglyceride oil based polymer‐silver nanocomposites were successfully prepared. The whole process was divided into two simultaneous stages; (i) copolymerization of macromonomers obtained from partial glycerides with styrene and (ii) the reduction of silver nitrate to metallic silver nano particles with radicals stemming from the thermolysis of 2,2′‐azoisobutyronitrile (AIBN). Nanocomposites were characterized by TEM and TGA. The obtained polymer nanocomposite was also examined in view of antibacterial effect against Gram‐positive, Gram‐negative, and Spore forming bacteria. It was demonstrated that nanocomposite samples exhibited an antibacterial effect against these bacteria. Film properties of the samples as potential coating material were also studied. Nanocomposite samples showed better film properties than that of the polymer without silver nanoparticles.     

Self-cleaning Anti-fouling TiO2/Poly(aryl ether sulfone) Composite Ultrafiltration Membranes

A series of novel TiO2/poly(aryl ether sulfone) ultrafiltration membranes with anti-fouling and self-cleaning properties was designed and prepared. First, anti-photocatalytic degraded fluorine contained polv(aryl ether sulfone) matrix(PAES-F) was synthesized. Then the composite membranes were prepared via TiO2 nanopartides and PAES-F polymer matrix by solution blending and non-solvent induced phase inversion methods. Further, separation efficiency, fouling behavior and self-cleaning property of the composite ultrafiltration(UF) membranes were investigated by dead-end filtration experiments using a polyacn lamide solution. The composite UF membranes exhibited outstanding self-cleaning efficiency and anti-photocatalytic degraded property after exposure to simulated sunliglit irradiation.The water flux recovery ratios(FRR)of the optimal composite UF membranes could reach 74.24%, which was attributable to photocatalytic degradation of the organic contaminant by TiO2. And the retention rates of the composite UF membranes could maintain over 97%, which indicated the excellent photocatalytic degradation resistance of the fluorine contained PAES-F matrix. The novel high perfomiance composite UF membranes have a broad application prospect in water treatment.     

Green synthesis and characterization of monodispersed silver nanoparticles obtained using oak fruit bark extract and their antibacterial activity

Green synthesis of silver nanoparticles (Ag NPs) has been achieved using oak fruit bark extract as a reducing, capping and stabilizing agent. The biosynthesized Ag NPs were characterized using various techniques. UV–visible spectrum of prepared silver colloidal solution showed absorption maximum at 433 nm. X‐ray diffraction and transmission electron microscopy analysis revealed that Ag NPs have a face‐centred cubic structure being spherical in shape with an average particle size of 20–25 nm. The toxicity of the Ag NPs was tested on bacterial species such as Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa and Escherichia coli by comparison based on diameter of inhibition zone in disc diffusion tests and minimum inhibitory concentration and minimum bactericidal concentration of NPs dispersed in liquid cultures. The antimicrobial activity of Ag NPs was greater towards Gram‐positive bacteria (S. aureus and B. subtilis) compared to Gram‐negative bacteria as determined using standard Kirby–Bauer disc diffusion assay and serial dilution. Copyright © 2016 John Wiley & Sons, Ltd.