Synergistic Effect of Chitosan and Metal Oxide Additives on Improving the Organic and Biofouling Resistance of Polyethersulfone Ultrafiltration Membranes.

The combination of chitosan and metal oxides was utilized as an addition to improve the fouling resistance of polyethersulfone (PES) ultrafiltration membranes. Pure water flux, membrane hydrophilicity by the contact angle, scanning electron micrographs, and Fourier-transform infrared spectra were used to characterize the membranes. With the addition of metal oxides, the modified membrane's water flux increased. The PES membrane with 0.25% wt chitosan and 2.0% wt AgNO3 had the highest flux and antibacterial activity among the membranes tested. Because of its potential to improve membrane hydrophilicity, the water flux increased with the addition of chitosan and AgNO3. Because of the improved hydrophilicity, the contact angle reduced as chitosan and Ag loading was increased. The PES-chitosan-Ag2O (from AgNO3 2.0% wt) membrane had high antibacterial activity against Escherichia coli and Staphylococcus aureus, whereas the PES-2.0% wt Ag membrane did not show the same result. Finally, the addition of chitosan in the PES-Ag membrane increased the membrane's antibacterial activity substantially.

Synthesis and characterization of sulfonated poly(eugenol-co-allyleugenol) membranes for proton exchange membrane fuel cells.

The research of sulfonated eugenol-allyleugenol copolymer (SPEAE) based membrane for fuel cell from eugenol derivate had been conducted. First, eugenol was reacted with various weights of allyl eugenol to form eugenol-allyleugenol copolymer (PEAE). Determination of the optimum composition of PEAE was done by testing the swelling properties. Then, PEAE was sulfonated using concentrated sulfuric acid with time variations of 1, 2, 3, 4, and 5 h to form SPEAE. The SPEAE produced was tested for the degree of sulfonation, water uptake, cation exchange capacity, and membrane proton conductivity. In addition, the characteristics of the PEAE and SPEAE copolymer membranes were also analyzed using FTIR spectrophotometers, 1H-NMR, TGA, and DSC. The results showed that the copolymerization of eugenol:allyleugenol (EG:AEG) with a ratio of 10:1 gave the lowest swelling degree. The best SPEAE copolymer was obtained from sulfonation for 2 h with yield, degree of sulfonation, water absorption value, proton conductivity, and cation exchange capacity of 90.6%, 12.87%, 50.7%, 1.83 × 10-5 S cm-1 and 0.356 meq/g, respectively. FTIR analysis shows the formation of PEAE with the loss of the vinyl eugenol groups used to form the polymer and shows the formation of SPEAE in the presence of sulfonate groups from the sulfonation reaction. 1H-NMR also confirmed the presence of the PEAE and SPEAE copolymers. In addition, analysis of thermal properties with TGA and DSC also showed that sulfonate treatment could improve membrane stability.

Green Synthesized Silver Nanoparticles Immobilized on Activated Carbon Nanoparticles: Antibacterial Activity Enhancement Study and Its Application on Textiles Fabrics.

This research aimed to enhance the antibacterial activity of silver nanoparticles (AgNPs) synthesized from silver nitrate (AgNO3) using aloe vera extract. It was performed by means of incorporating AgNPs on an activated carbon nanoparticle (ACNPs) under ultrasonic agitation (40 kHz, 2 × 50 watt) for 30 min in an aqueous colloidal medium. The successful AgNPs synthesis was clarified with both Ultraviolet-Visible (UV-Vis) and Fourier Transform Infrared (FTIR) spectrophotometers. The successful AgNPs-ACNPs incorporation and its particle size analysis was performed using Transmission Electron Microscope (TEM). The brown color suspension generation and UV-Vis's spectra maximum wavelength at around 480 nm confirmed the existence of AgNPs. The particle sizes of the produced AgNPs were about 5 to 10 nm in the majority number, which collectively surrounded the aloe vera extract secondary metabolites formed core-shell like nanostructure of 8.20 ± 2.05 nm in average size, while ACNPs themselves were about 20.10 ± 1.52 nm in average size formed particles cluster, and 48.00 ± 8.37 nm in average size as stacking of other particles. The antibacterial activity of the synthesized AgNPs and AgNPs-immobilized ACNPs was 57.58% and 63.64%, respectively (for E. coli); 61.25%, and 93.49%, respectively (for S. aureus). In addition, when the AgNPs-immobilized ACNPs material was coated on the cotton and polyester fabrics, the antibacterial activity of the materials changed, becoming 19.23% (cotton; E. coli), 31.73% (polyester; E. coli), 13.36% (cotton; S. aureus), 21.15% (polyester; S. aureus).

Variability of TOC and DBPs (THMs and HAA5) in drinking water sources and distribution system in drought season: the North Iran case study.

The aim of this study is tracing seasonal variability of total organic carbon (TOC), trihalomethanes (THMs) and haloacetic acids (HAA5) as disinfection by-products (DBPs) in drinking water sources and the distribution system in the north of Iran. The results showed that the concentrations of TOC were within the range of 0.013-1.42 mg/L. In addition, the results showed that most of the water sources had nearly the same concentration level (i.e. <1 mg/L), with the exception of one peak for groundwater source and middle drinking water distribution system in the city of Sari (1.42 mg/L) and Babol (1.37 mg/L). It was demonstrated that brominated HAA (MBAA) presented the highest concentration in the Sari City (17.3 µg/L) followed by the City of Behshahr (8.9-11.19 µg/L). The Babol City showed the highest concentration of chlorinated HAA (22.403 and 22.503 µg/L for DCAA and TCAA, respectively). Among the different compounds of THMs, the concentration of CHBr3 was nearly in the same order of magnitude in the cities of Sari, Babol and Behshahr for both spring and summer seasons. The brominated THM (BDCM) concentrations were also high (14.7 µg/L) in the Behshahr City. The results of independent t-test indicated that the seasonal (spring and summer) difference was statistically significant in the case of temperature and TTHM (p < 0.05). Furthermore, total HAA5 ≤ 60 µg/L and THM ≤100 µg/L in all the considered cities over the period of the study. The TTHMs concentration was 56 µg/L in treating surface water (TSW) source in the summer season at the Sari city.

Ionic Conductivity and Cycling Stability Improvement of PVDF/Nano-Clay Using PVP as Polymer Electrolyte Membranes for LiFePO4 Batteries.

In this paper, we present the characteristics and performance of polymer electrolyte membranes (PEMs) based on poly(vinylidene fluoride) (PVDF). The membranes were prepared via a phase-inversion method (non-solvent-induced phase separation (NIPS)). As separators for lithium battery systems, additive modified montmorillonite (MMT) nano-clay served as a filler and poly(vinylpyrrolidone) (PVP) was used as a pore-forming agent. The membranes modified with an additive (8 wt % nano-clay and 7 wt % PVP) showed an increased porosity (87%) and an uptake of a large amount of electrolyte (801.69%), which generated a high level of ionic conductivity (5.61 mS cm−1) at room temperature. A graphite/PEMs/LiFePO4 coin cell CR2032 showed excellent stability in cycling performance (average discharge capacity 127 mA h g−minus;1). Based on these results, PEMs are promising materials to be used in Polymer Electrolyte Membranes in lithium-ion batteries.

Immobilization of glucose oxidase on chitosan-based porous composite membranes and their potential use in biosensors.

The glucose oxidase (GOx) enzyme was immobilized on chitosan-based porous composite membranes using a covalent bond between GOx and the chitosan membrane. The chitosan-based porous membranes were prepared by the combination of the evaporation- and non-solvent-induced phase separation methods. To increase the membrane conductivity, carbon nanotubes (CNTs) were added to the chitosan solution. The resulting membranes were characterized in terms of water permeability, surface morphology and surface chemistry. Enzyme immobilization was performed on the chitosan membranes with and without activation using glutaraldehyde (GA). Three different configurations of working electrodes were evaluated to investigate the potential use of the modified membranes in biosensors. The results show that enzyme immobilization capacity was greater for membranes that had been activated than for membranes that had not been activated. In addition, activation increased the stability of the enzyme immobilization. The immobilization of GOx on chitosan-based membranes was influenced by both pH and the concentration of the enzyme solution. The presence of CNTs significantly increased the electrical conductivity of the chitosan membranes. The evaluation of three different configurations of working electrodes suggested that the third configuration, which was composed of an electrode-mediator-(chitosan and carbon nanotube) structure and enzyme, is the best candidate for biosensor applications.

Influences of solution chemistry and polymeric natural organic matter on the removal of aquatic pharmaceutical residuals by nanofiltration.

This study demonstrates the removal efficiency and the permeate flux behavior during cross-flow nanofiltration (NF) of aqueous solutions of five pharmaceutically active compounds (PhACs). Cephalexin, tetracycline, acetaminophen, indomethacin and amoxicillin were used as models of PhACs, and alginate was selected as model of natural organic matter (NOM). Two commercial composite NF membranes (SR2 and SR3) with different characteristics were used. The highest rejection was observed for tetracycline, i.e., 75-95% for membrane SR 2 and 95-100% for membrane SR 3, while the rejection was least for acetaminophen (32-36% for SR2 and 52-59% for SR3). As the pH of acetaminophen solution was increased (from 6 to 9) the rejection would increase. Changes of ionic content (from 10 to 20mM) lead to increase (from 89 to 93% for SR 3) or decrease (from 100 to 91% for SR2) of cephalexin rejection depending on the membrane used. The permeate flux would decrease with decreasing the pH solution and increasing ionic strength. The addition of alginate in the feed stream decreased the permeate flux, with lower reduction for SR3, and increased the PhAC rejection except for acetaminophen and amoxicillin. Both size and Donnan exclusions seemed to occur, and the effect of Donnan exclusion was more pronounced for the NF membrane having larger effective pore size (SR2).

High-performance thin-layer hydrogel composite membranes for ultrafiltration of natural organic matter.

Thin-layer hydrogel composite (TLHC) ultrafiltration (UF) membranes were synthesized by photo-grafting of either poly(ethylene glycol) methacrylate (PEGMA) or N,N-dimethyl-N-(2-methacryloyloxyethyl-N-(3-sulfopropyl) ammonium betaine (SPE) onto commercial polyethersulfone (PES) UF membranes. The performance of TLHC UF membranes was evaluated for natural organic matter (NOM) filtration and compared to commercial PES UF membranes. The fouling evaluation was done by investigation of membrane-solute interactions (adsorptive fouling) and membrane-solute-solute interactions (UF). The results suggest that the TLHC membranes convincingly displayed a higher adsorptive fouling resistance than unmodified PES UF membranes. In long-term stirred dead-end UF, a much lower fouling was observed for TLHC membranes than for commercial membranes with the same flux and rejection. Further, water flux recovery was also much higher. An analysis using an existing blocking model was performed in order to elucidate the effect of a polymer hydrogel layer on fouling mechanism as well as cake layer characteristics. The TLHC membranes synthesized by photo-grafting of PEGMA (40 g/L) and PEGMA with a low concentration of cross-linker monomer in the reaction mixture (ratio: 40/0.4 (g/L)/(g/L)) showed a much better performance than the other composite membranes. Those membranes could reduce the cake resistance on the membrane surface. This work has relevance for the design of high-performance UF membranes for applications in water treatment.

Photografted thin polymer hydrogel layers on PES ultrafiltration membranes: characterization, stability, and influence on separation performance.

Highly fouling-resistant ultrafiltration (UF) membranes were synthesized by heterogeneous photograft copolymerization of two water-soluble monomers, poly(ethylene glycol) methacrylate (PEGMA) and N,N-dimethyl-N-(2-methacryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPE), with and without cross-linker monomer N,N'-methylene bisacrylamide (MBAA), onto a polyethersulfone (PES) UF membrane. The characteristics, the stability, and the UF separation performance of the resulting composite membranes were evaluated in detail. The membranes were characterized with respect to membrane chemistry (by ATR-IR spectroscopy and elemental analysis), surface wettability (by contact angle), surface charge (by zeta potential), surface morphology (by scanning electron microscopy), and pure water permeability and rejection of macromolecular test substances (including the "cutoff" value). The surface chemistry and wettability of the composite membranes did not change after incubating in sodium hypochlorite solution (typically used for cleaning UF membranes) for a period of 8 days. Changes in water permeability after static contact with solutions of a model protein (myoglobin) were used as a measure of fouling resistance, and the results suggest that PEGMA- and SPE-based composite membranes at a sufficient degree of graft modification showed much higher adsorptive fouling resistance than unmodified PES membranes of similar or larger nominal cutoff. This was confirmed in UF experiments with myoglobin solutions. Similar results, namely, a very much improved fouling resistance due to the grafted thin polymer hydrogel layer, were also obtained in the UF evaluation using humic acid as another strong foulant. In some cases, the addition of the cross-linker during modification could improve both permeate flux and solute rejection during UF. Overall, composite membranes prepared with an "old generation" nonfouling material, PEGMA, showed better performance than composite membranes prepared with a "new generation" one, the zwitterionic SPE.