GO and GO-TiO2 incorporation in TFN membrane by interfacial polymerization for excellent water vapor separation performance.
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•GO and GO-TiO2 nanofillers were incorporated in polyamide ...nanocomposite membrane.•Improved water vapor permeance was obtained from GO and GO-TiO2 nanofillers incorporated TFN membranes.•Highly hydrophilic TFN membranes were obtained for water vapor separation.•GO-TiO2 shows superior water vapor permeance than GO.•Functionalized GO could improve water vapor permeation even further.
Graphene oxide (GO) and its composite with TiO2 (GT) were utilized as nano-filler materials to prepare highly permeable and water vapor selective nanocomposite membranes. The nano-fillers were characterized using different analytical tools to determine their physicochemical properties. Nanocomposite membranes were prepared by dispersing the nano-fillers in aqueous phase monomer solution for interfacial polymerization reaction on the inner surface of Polysulfone hollow fiber membrane. Surface morphology and bonding chemistry of the nanocomposite membrane was analyzed using various analytical tools. The two types of nano-fillers were compared for their compatibility with the polyamide matrix, and consequently, the water vapor separation performance of the resulting membrane. Results revealed that both the nano-fillers are firmly attached to the polyamide layer via hydrogen and covalent bonds. GT based membranes have higher surface roughness and better hydrophilicity as compared to GO. In addition, GT membranes have more carboxyl groups and lesser degree of cross-linking due to the interference with interfacial polymerization reaction. This leads to a higher permeance (2820 GPU) and a water vapor/nitrogen selectivity when compared to other TFN membranes reported in literature. The nano-fillers act as active sites for preferential transport of water vapor molecules through the membrane thereby, significantly improving water vapor permeance.
Flexible hydrogen gas (H2) sensors are fabricated using a single layer graphene decorated with palladium (Pd) nanoparticles. Thermally evaporated Pd is generally deposited on a graphene in the form ...of nanoparticles when the deposition thickness is very small. The graphene sensor with Pd thickness of 3nm exhibits a gas response of ∼33% when exposed to 1000ppm H2 and it is able to detect as low as 20ppm H2 at room temperature (22°C). The sensor is so flexible that any significant degradation is not observed when it is bent to a curved geometry with a bending radius of 3mm. The flexible hydrogen sensors are applicable to a broad range of systems with demanding mechanical flexibility, durability and high gas response.
Amphiphilic graft copolymers consisting of poly(vinyl chloride) (PVC) main chains and polymerized ionic liquid (PIL) side chains were synthesized via atom transfer radical polymerization (ATRP). ...Successful synthesis of the graft copolymers was confirmed using 1H nuclear magnetic resonance (1H NMR), Fourier-transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) analysis. Differential scanning calorimetry (DSC), transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS) analysis revealed well-defined microphase-separated structures in the hydrophobic PVC and the hydrophilic PIL domains. Thus, the PVC-g-PIL graft copolymer membranes maintained good mechanical properties (i.e. a lower strength and greater elongation than PVC) without losing separation properties, as confirmed by universal tensile machine (UTM) and mixture gas permeation tests of CO2/N2 (50/50) at 35°C. As the content of PIL increased, the CO2 permeability increased with a slight decrease of selectivity. The CO2 permeability of PVC-g-PIL membrane with 65wt% of PIL reached 17.9Barrer at 35°C, which was approximately ten times higher than that of the pristine PVC membrane (1.7Barrer). Upon utilizing a PVC-g-PIL/IL composite with 15wt% IL, the CO2 permeability increased to 137.6Barrer by approximately 7.7-fold with a moderate decrease of selectivity.
•Microphase-separated structures were obtained for PVC-g-PIL graft copolymers.•Membrane performance increased with PIL content.•Good mechanical properties were obtained without losing separation properties.•High permselective properties were obtained for free-standing PVC-g-PIL and PVC-g-PIL/IL composite membranes.
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•Pore-filling method successfully converted a porous HDPE hollow fiber membrane with large pores into a non-porous membrane for stable water vapor separation.•Pore-filling solution ...used glycerin/PVA/GA, which forms into a hydrogel through physicochemical cross-linking.•Higher the viscosity of the pore-filling solution, more of the large pores were blocked.•However, excess concentration (related to high viscosity) of the pore-filling solution negatively impacted the pore-filling process.•Pore-filled composite membrane consists of a hydrogel that can be washed and recharged, allowing it to be rechargeable.
We propose a new method of using high-density polyethylene (HDPE) ultrafiltration hollow fibers, which are inexpensive but difficult to use as a dehumidification membrane. Dehumidification membranes have a wide range of applications and can also offer the benefit of water recovery. Conventional membranes for gas separation consist of a substrate and a thin layer that selectively permeates a desired gas. However, low-cost substrates such as HDPE are limited in their application due to the presence of large pores that prevent defect-free thin layer formation. To address the issue of large pores, we utilized hydrogels made from viscous solutions, that can be stably positioned in large pores. Specifically, we filled the pores of the HDPE substrate with hydrogels consisting of glycerin, polyvinyl alcohol (PVA), and glutaraldehyde (GA). The pore-filled membranes capable of separating water vapor were 40GPGM and 50GPGM, which were filled with 40GPM (40 wt% glycerin/1 wt% PVA/0.5 wt% GA) and 50GPG (50 wt% glycerin/1 wt% PVA/0.5 wt% GA), respectively. Since the pore-filled membranes were filled with viscous hydrogels, they could be washed and recharged. Accordingly, they showed good rechargeability when measuring properties during multiple pore-filling and washing processes. The water vapor permeance/selectivity/water flux of the pore-filled membranes were measured at various temperatures and feed flow rates. The water vapor permeance/selectivity/water flux of 40GPGM and 50GPGM measured at 35 °C and 3.5 L/min were 3400 GPU/110/0.12 kg/m2∙hr and 2398 GPU/469/0.14 kg/m2∙hr, respectively. After continuous operation for 30 days, it was confirmed that the pore-filled membranes had good long-term stability.
•Double network ultrathin layer was coated over polysulfone membrane.•Quaternary polyethyleneimine has a positive impact on membrane performance.•Maximum water vapor permeance increased up to 8115 ...GPU.•Maximum selectivity for water vapor over nitrogen up to 511.•RH% was reduced from 85% to 37%.•Water vapor flux reaches up to 0.67 Kg/m2/hr.
Here we present, for the first time, ultrathin double network (DN)-coated hollow fiber membranes to improve water vapor permeation of polymeric membranes. In this study, we investigated two different DN systems. The hyperbranched polyethyleneimine (HPEI) and its quaternized HPEI form (QHPEI) represented the first network in both systems, while the second network was based on quaternized polyacrylic acid (QACC) and quaternized poly (2-acrylamido-2-methyl-1-propanesulfonic acid) (QAMPS). Various analysis techniques were used to characterize QHPEI and DN-coated polysulfone (PSf) membranes. Water vapor permeation experiments were conducted at QHPEI concentration in total precursor (QHPEI and HPEI) and different operating parameters. The incorporation of a higher QHPEI amount improved the hydrophilicity and water vapor performance of DN-coated membranes. QAAC-100 and QAMPS-100 exhibited the highest performance in each system; however, QAMPS showed higher water vapor permeance (P) and lower selectivity (S). This behavior was attributed to the presence of a bulkier pendant group (i.e. less compact), higher hydrophilicity, and a thinner membrane in QAMPS compared to QAAC. The increment in relative humidity (RH) illustrated a positive effect on the membrane performance, while both temperature and pressure illustrated a negative impact. The best performance obtained by QAAC-100 (S = 511, P = 5825 GPU) and QAMPS-100 (S = 422, P = 8115 GPU) was achieved at 1 bar as feed pressure, 75% as RH, 35 °C as operating temperature, and 1 L/min as feed gas flow rate.
The purpose of this study was to recycle red mud, an industrial byproduct that generates 300,000 tons per year, into the construction industry. Red mud was prepared as a liquid, neutralized with ...sulfuric acid, and replaced with cement mortar. The properties of liquefied red mud (LRM) neutralized with sulfuric acid (LRM + S) were investigated as well as its effect on cement mortar's mechanical and hydration characteristics. The pH of LRM + S stabilized at 7.6; its SO
content was ~4.19% higher than that of LRM. Sulfites were contributed by calcium and sodium sulfate. The flows and setting times of the mortars containing LRM and LRM + S decreased as the substitution rate increased. The compressive strength of mortar that replaced 5% of cement with LRM + S was similar to that of the plain cement mortar. Scanning electron microscopy and X-ray diffraction revealed that the hydration products of LRM + S-containing cement mortar were similar to those of the plain cement mortar. Thus, LRM + S can be used as a cement substitute.
In this work, we have reported a facile method to improve the water vapor permeation performance of thin film nanocomposite membranes by tailoring the surface properties of Silicon nanoparticles. ...Inductively coupled plasma technique was utilized to synthesize amorphous Silicon nanoparticles (~10nm) which were immediately dispersed in alcohol solvents to functionalize the hydrogenated surface. The major aim was to increase the loading capacity of nanoparticles in the polyamide membrane without sacrificing the membrane performance. The nanoparticles were then added to the aqueous phase monomer for interfacial polymerization reaction to form a polyamide nanocomposite membrane. The physicochemical properties of the nanocomposite membranes were investigated using electron microscopy, surface roughness profiling, water contact angle, and X-ray photoelectron spectroscopy. The isopropyl alcohol (IPA) dispersed nanoparticles showed better hydrophilicity and higher surface roughness than ethanol counterparts. Mixed gas permeation tests indicated that the addition of nanoparticles in the polyamide membrane increases the water vapor permeation due to the excess sorption sites provided by the nanoparticles. The degree of polyamide cross-linking decreased in modified membranes as compared to the pristine polyamide membrane. Nonetheless, the increase in hydrophilicity compensated for the membrane selectivity. Furthermore, isopropyl alcohol dispersed nanoparticles showed higher permeance, flux, and selectivity even at higher concentrations indicating a uniform dispersion in the polyamide membrane. A maximum water vapor permeance of 2125GPU with vapor/gas selectivity of 581 was observed for nanocomposite membranes containing 1.0wt% IPA dispersed Silicon nanoparticles.
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•Amorphous Silicon nanoparticles were synthesized in alcohol based solvents.•Fabrication of nanocomposite membranes using functionalized nanoparticles.•The nanoparticles addition increased the surface hydrophilicity and roughness.•Functionalized nanoparticles showed higher cross-linking density.•Isopropyl alcohol based nanoparticles shoed higher loading capacity and permeance.
This study focuses on improving the CO₂ permeability and stability of the liquid membrane. To improve permeability, polymeric hollow fiber support with a high effective area per unit volume were ...prepared with various dope composition as a support; to improve stability, the effects of varying the structure of the support and immobilization conditions were observed and analyzed. For the experiment, 1-ethyl-3-methylimidazolium-bis(trifluoromethylsulfonyl) imide (emimTf₂N) and polyvinylidene fluoride (PVDF) were used. For immobilization of the emimTf₂N, the liquid was diluted to 40vol.% in methanol and immobilized liquid membranes (ILMs) were prepared as gas permeation modules. The prepared ILM module was characterized by single gas permeation of CO₂ and N₂ according to feed pressure at atmosphere temperature. All of prepared modules were observed with high CO₂ permeability of over 2600 barrer, respectively. However, stability on pressure was affected by support structure.
