A high-strength polyvinyl alcohol hydrogel membrane crosslinked by sulfosuccinic acid for strontium removal via filtration

This study considered the removal of strontium (Sr2+) from contaminated water using a filtration membrane that exhibits good mechanical strength, high adsorption capacity, and the ability to be regenerated and reused. Polyvinyl alcohol hydrogel membranes were prepared by crosslinking with sulfosuccinic acid in different ratios (2.5, 5, 10 and 20 mol% relative to the PVA monomer), named as PSA2.5, PSA5, PSA10 and PSA20. All PSA membranes showed good Sr2+ adsorption over a wide pH range (pH 2–12), and maintained rapid removal kinetics (> 95% Sr2+ recovered from 5 ppm Sr2+ within 4 h). Furthermore, the Sr2+ adsorption capacities of PSA2.5, PSA5, PSA10 and PSA20 were 27.6, 45.8, 56.3, and 55.3 mg/g, respectively, based on the Langmuir adsorption isotherm. From the four PSA membranes, PSA5 was selected for further filtration studies due to its favorable mechanical and adsorption properties. When filtering 5 ppm Sr2+ and 250 ppm Ca2+, corresponding to the Ca2+ concentration in the wastewater at the Fukushima nuclear plant, 87% Sr2+ was removed using the PSA5 membrane following multiple cycles of regeneration and reuse. Moreover, the tensile strength of the PSA5 membrane remained high (> 100 MPa) following five consecutive uses

Gas separation performance of 6FDA-DAM-ZIF-11 mixed-matrix membranes for H-2/CH4 and CO2/CH4 separation

In this study, gas separation performance of 6FDA-DAM-ZIF-11 mixed matrix membranes (MMMs) with various ZIF-11 percentages (0, 10, 20, 30 wt.%) were investigated. Scanning electron microscopy (SEM), X-ray diffraction (XRD), and particle size analysis were achieved to investigate ZIF-11 structure. SEM, Fourier Transform Infrared Spectroscopy (FT-IR), Differential Scanning Calorimetry (DSC) and thermogravimetric (TGA) analysis were also carried out to characterize the membranes. In the SEM images of the MMMs, no apparent agglomeration between ZIF-11 particles and the 6FDA-DAM matrix was observed, even at 30 wt.% loading of the ZIF-11. The measured permeabilities for H-2, CO2 and CH4 gases were found to be 272, 257 and 8.3 Barrers for 20 wt.% ZIF-11 containing MMMs measured at 30 degrees C and 4 bar. Pure gas permeation tests showed improvement in permeability of the MMMs but the ideal selectivity of gases remained almost constant for the various loadings. The permeability values increased as the ZIF-11 loading increased up to 20 wt.%. However, at higher loadings, 30 wt.%, the permeability decreased for all gases. The ideal selectivities of MMMs did not show significant change but the selectivity of 6FDADAM-ZIF-11 at 20 wt.% loading approached to the 2008 Robeson upper bound. (C) 2016 Elsevier B.V. All rights reserved

The preparation of novel silica modified polyimide membranes: synthesis, characterization, and gas separation properties

In this study, new monomers having siloxane groups were synthesized as an intermediate for preparation of siloxane modified polyimide polymers. Then with these monomers, the synthesis of uncrosslinked and crosslinked polyimide-siloxane hybrid polymer membranes were achieved. The purposes of the preparation of modified polyimides were to modify the thermal and chemical stability, and mechanical strength of polyimides, and to improve the gas separation properties of polymers. The new diamine monomer having siloxane groups was prepared from 3,5-diaminobenzoic acid (3,5-DABA) and 3-aminopropyltrimethoxysilane (3-APTMS) in N-methyl-2-pyrollidone (NMP) at 180 degrees C. The modified polyimide membranes having different amount of siloxane groups were synthesized from pyromellitic dianhydride (PMDA), 4,4-oxydianiline (ODA), and 3,5-diaminobenzamido-N-propyltrimethoxy silane (DABA/PTMS) in NMP using a two-step thermal imidization process. The synthesis of modified polyimide membranes were characterized by Fourier transform infrared spectroscopy (FTIR). The thermal analysis of the polyimides were carried out by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Water absorption and swelling experiments were also carried out for the investigation of structural properties of polymers. FTIR observations confirmed that the polyimide membranes with new diamine intermediate were successfully obtained. Thermal analysis showed that the uncrosslinked copolyimides exhibited two glass transition temperatures, indicating that they were separated microphases and it was found that all the modified copolyimides had showed higher glass transition temperature (T(g)) than unmodified polyimides. The separation properties of the prepared polyimide membranes were also characterized by permeability for O(2) and N(2) gases and ideal selectivity values were calculated. Copyright (C) 2009 John Wiley & Sons, Ltd

Calamitic Liquid Crystals as Additive Materials to the Organic Solar Cells

A bilayer polymer solar cell has been shown with the device configuration ITO/PEDOT:PSS/P3HT(poly(3-hexyl-thiophene))/C60/Al. In this article we have been reported the effect of two different liquid crystals which have different terminal chains to the bilayer organic solar cells. Based on photovoltaic measurements, we have been compared the efficiency enhancement for bilayer heterojunction solar cells using calamitic liquid crystals (LC1 and LC2). In this respect current-voltage characteristics of devices have been compared with LC1 and LC2. It has been determined that adding LC1 and LC2 increases the device parameters of bilayers. It has been also understood that the fill factor (FF) of the device has been significantly increased from 0.35 to 0.48 with adding LC1 which contain oxygen

Enhanced gas transport properties of mixed matrix membranes consisting of Matrimid and RHO type ZIF-12 particles

Zeolitic imidazolate frameworks (ZIF) have been showed as potential active inorganic fillers in high-performance gas separation membranes. Among them, zeolitic imidazolate framework-12 crystals were synthesized as a porous filler material by alcohol-based solution method using benzimidazole-toluene interactions and they were incorporated into a commercial glassy polyimide Matrimid 5218 with various ZIF-12 loadings (0, 10, 20, 30, 40 wt.%), as the continuous phase. As-synthesized ZIF-12 was characterized by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), multipoint Brunauer-Emmett-Teller (BET) surface analysis, Fourier Transform Infrared Spectroscopy (FT-IR) and Thermogravimetric Analysis (TGA). SEM images of ZIF-12 particles assert regular external surfaces with a rhombic dodecahedron structure. Matrimid mixed matrix membranes (MMMs) loaded with different amounts of ZIF-12 were prepared by solution casting method and characterized by XRD, FT-IR, TGA and SEM analyses. Our findings showed that there was a good dispersion and wetting of ZIF-12 particles in the continuous phase. Gas transport properties of the membranes were investigated by single gas permeation experiments of H-2, CO2 and CH4 at 4bar feed pressure and 35 degrees C. The permeability values increased as the ZIF-12 loading increased up to 20 wt.%. However, at higher loadings, 30 and 40 wt.%, the permeability decreased for all gases and the CO2/CH4 and H-2/CH4 selectivities increased depending on the influence of the ZIF-12 filler. The maximum ideal separation factor for CO2/CH4 and H-2/CH4 were found about 66.70 and 212.00, significantly higher than the pure polymer ideal separation factor. (C) 2017 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved

Fabrication and characterization of silica modified polyimide-zeolite mixed matrix membranes for gas separation properties

In this study, new monomers having silica groups were synthesized as an intermediate for the preparation of poly(imide siloxane)-zeolite 4A and 13X mixed matrix membranes (MMMs). The effects of membrane preparation steps, zeolite loading, precursor's composition, and pore size of zeolite on the gas separation performance of these mixed matrix membranes were studied. The new diamine monomer was prepared from 3,5-diaminobenzoic acid (3,5-DABA), 3-aminopropyltrimethoxysilane (3-APTMS), and zeolite 4A and zeolite 13X in N-methyl-2-pyrollidone (NMP) at 180 degrees C. Poly(imide siloxane)-zeolite 4A and 13X MMMs were synthesized from pyromellitic dianhydride (PMDA) and 4,4-oxydianiline (ODA) in NMP using a two-step thermal imidization. SEM images of the MMMs show the interface between polymer and zeolite phases getting closer when surface modified zeolite is used. The increase in glass transition temperature (T-g) confirms the polymer chain becoming more rigid induced by the presence of zeolite. The experimental results indicated that a higher zeolite loading resulted in a decrease in gas permeability and an increase in gas pair selectivity. In terms of O-2 and N-2 permeance and ideal selectivity, the separation performances of poly(imide siloxane)-zeolite MMMs were related to the zeolite type and zeolite pore dimension

ZIF-11/Matrimid (R) mixed matrix membranes for efficient CO2, CH4, and H-2 separations

Zeolitic imidazolate framework ZIF-11 particles were prepared and mixed with Matrimid (R) 5218 polyimide, from 0 to 40 wt. % loadings. The ZIF-11 particles and the Matrimid (R) 5218 polyimide matrix were studied using differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), X-Ray diffraction (XRD), infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM) techniques. Surface and cross-sectional scanning electron microscopy images of the mixed matrix membranes (MMMs) were taken to examine the dispersion of particles in the polymer matrix. No visible agglomeration between ZIF-11 particles and the polymer matrix was spotted, even at 40 wt. % ZIF-11 loading. Mixed matrix membranes were described by the measured permeabilities of H-2, CO2 and CH4 gases. Ideal gas selectivities were determined. Permeability of all gases increased with increasing ZIF-11 percentages. The permeabilities for all gases decreased at 40 wt. % loading, and the CO2/CH4, and H-2/CH4 selectivities were increased. (c) 2018 Society of Chemical Industry and John Wiley & Sons, Ltd

Synthesis of high surface area ZnO powder by continuous precipitation

Synthesis of high surface area ZnO powder was achieved by continuous precipitation using zinc ions and urea at low temperature of 90 degrees C. The powder precipitated resulted in high-purity single-phase ZnO powder when calcined at 280 degrees C for 3 h in air. The solution pH and the precipitation duration strongly affected the surface area of the calcined ZnO powder. Detailed structural characterizations demonstrated that the synthesized ZnO powder were single crystalline with wurtzite hexagonal phase. The powdered samples precipitated by homogeneous precipitation crystallized directly to hydrozincite without any intermediate phase formation

Hydrogen production by photocatalytic water-splitting using nitrogen and metal co-doped TiO2 powder photocatalyst

Nitrogen-doped titanium dioxide (N-TiO2) powders were synthesized by hydrolysis and used as a support for doping with various metals, such as, Fe, Cr, Ni, and Pt. Aqueous solutions of metal salts were used as a metal source and metals were deposited on N-TiO2 powders. Ni-N-TiO2 catalysts with various nickel concentrations were studied in detail. X-ray diffraction and diffuse reflectance spectrophotometry were used for the characterization of the photocatalysts. The Ni-N-TiO2 photocatalysts were then tested in photocatalytic water splitting under visible light. The optimum dopant concentration was found to be 10 mu mol Ni/g N-TiO2 for Ni-N-TiO2. The photocatalyst, Ni-N-TiO2, has shown a stable and high activity, 490 mu mol of H-2 g(cat)(-1) h(-1) for the first 6 h of operation