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

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

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

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

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