Display omitted
•High quality GO membranes can be coated on polymer substrate by spray coating method.•Prepared GO membranes offer gas characteristics similar to those made by filtration.•Dilute GO ...suspension in spray coating reduces the formation of extrinsic wrinkles.•Less wrinkles results in reduction in the porosity of inter-layer galleries.•Less wrinkles leads to higher selectivity of H2 over large gas molecules.
Graphene oxide (GO) membranes have shown promising gas separation characteristics specially for hydrogen showing potential for industrial applications. However, GO membranes made by filtration, the most common synthesis method, contain wrinkles affecting their gas separation characteristics and the method itself is difficult to scale up. In this work, high quality GO membranes are made from GO suspension by easily scalable spray coating technique (and also by filtration method for comparison) on hydrophilic polyester track etch substrates. GO sheet suspensions of large sheet average size (33 µm) and dilute concentrations are used to minimize GO sheet edge-to-edge interactions and minimize extrinsic wrinkle formation. Single gas permeation and separation experiments of equimolar H2/CO2 binary mixture were conducted to evaluate the permeation and separation characteristics of prepared membranes. GO membranes prepared by spray coating offer gas characteristics similar to those made by filtration, however using dilute GO suspension in spray coating reduces the formation of extrinsic wrinkles causing reduction in the porosity of the inter-sheet pathway where the transport of large gas molecules dominates. This study demonstrates an efficient, scalable and cost-effective approach for synthesizing large area GO membranes with enhanced hydrogen separation.
The effect of the annealing temperature of polybenzimidazole (PBI) membranes on H2/CO2 gas separations was investigated. Membranes annealed from 250 °C to 400 °C were tested for gas permeation with ...pure H2, CO2, and N2 gases and a H2:CO2 (1:1) mixture at 35 °C, 100 °C, 200 °C, and 300 °C and at pressures up to 45 bar. Gas permeation data show that permeability and selectivity of the membranes is significantly impacted by the annealing temperature, the presence of adsorbed water, and remaining casting solvent (DMAc). At a testing temperature of 35 °C, ideal H2/CO2 selectivities of 50, 49, and 66 with pure H2 permeabilities of 1.5, 0.8, and 1.5 Barrer were obtained for membranes annealed at 250 °C, 300 °C, and 400 °C, respectively. At this temperature, high gas mixture H2/CO2 selectivities of 41, 73, and 47 with H2 permeabilities of 1.03, 0.26, and 0.50 Barrer were also obtained for these membranes. At testing temperatures of 300 °C, both the ideal and gas mixture H2/CO2 selectivities dropped to 44, 28, and 30 (ideal, H2 = 45, 45, 44 Barrer) and to 19, 22, and 23 (mixture, H2 = 41, 43, and 44 Barrer) for membranes annealed at 250 °C, 300 °C, and 400 °C, respectively. As water was removed from the membranes at temperatures greater than 100 °C during permeation cycles, where the testing temperature was increased from 35 °C to 300 °C, the permselectivity properties of the membranes annealed at 400 °C became more reproducible. Permeabilities at 35 °C from a second permeability cycle increased, but H2/CO2 selectivities decreased to 21 for gas mixtures (H2 = 1.4 Barrer) and to 34 for pure gases (H2 = 2.2 Barrer). The results suggest that high annealing temperatures may induce changes in the configuration and conformation of the polymer chains, imparting distinctive permselectivity properties to the membranes. Activation energies of permeability for H2, CO2, and N2 from pure gases and H2:CO2 mixtures correlated with these changes as well.
Display omitted
•Annealing PBI membranes at 300 °C–400 °C improves gas permeation properties.•Annealing at 300 °C–400 °C completes conversion of prepolymer into PBI.•Casting solvent and water released from polybenzimidazole membranes up to 400 °C.•Adsorbed water affects gas permeation at testing temperatures of up to 150 °C.•H2/CO2 gas mixture separation performance retained up to 300 °C and 30 bar.
•Chitosan-based mixed matrix composite membranes were characterized regarding physicochemical and separation propertes.•CO2/CH4 mixed gas separation was evaluated experimentally to validate a simple ...mathematical simulation model developed in our group.•Hydrophilicity and ion exchange compatibility of the components in the chitosan mixed matrix layer led to higher CO2/CH4 selectivities.•CO2/CH4 separation performance was better for 3D ETS-10 and zeolite 4A as fillers in chitosan based layer than 2D AM-4•The model validated the CO2/CH4 separation in a wide range of feed concentrations.
Membrane technology is acknowledged as one of the most efficient for biogas upgrading, separating simultaneously CH4 and CO2 in the retentate and permeate streams, respectively. The sustainability would still be improved by using renewable and environmentally friendly materials for membrane fabrication. Specifically, this study is focused on laboratory-scale mixed gas separation tests of composite membranes prepared from chitosan (CS), a hydrophilic, biodegradable and biocompatible polymer from abundant natural resources, with good adhesive and film forming properties and high affinity for CO2 due to the primary amine and hydroxyl groups functionalities in CS. To improve mechanical resistance and CO2/CH4 separation, CS was hybridized by a 5 wt% loading of non-toxic ionic emimacetate liquid (IL), and variable loadings of compatible inorganic fillers, such as 3D zeolite 4A and NaETS-10, and layered AM-4 titanosilicate. The CS-based mixed matrix layer was coated on porous polyether sulfone (PES) support. The CO2 permeance and CO2/CH4 separation were measured at different feed concentrations to evaluate the membranes performance in the treatment of different streams. This separation behavior was explained by the wet thickness, water uptake, morphology and ionic resistance of the composite membrane. As such, the 5 wt% Zeolite 4A and NaETS-10-filled ILCS/PES membranes provided a good dispersion in the ILCS matrix and the mixed matrix layer a good adhesion with the porous PES support, leading to high CO2 permeances and separation factors up to 30, whereas the more hydrophilic lamellar AM-4 titanosilicate-filled ILCS layer showed cluster agglomeration in the matrix and a faster detachment of the coated layer from the PES substrate. With increasing filler loading, an increase of the permeance of both CO2 and CH4 gas components was, although selectivity decreased upon increasing AM-4 filler loading. The CO2/CH4 mixed gas separation performance was validated by a custom-built model for a wide range of feed composition, to cover such processes as natural gas sweetening, biogas upgrading and enhanced oil recovery with acceptable relative error below 10% (absolute value), except for the AM-4 titanosilicate-filled ILCS membranes, showing morphological fabrication defects.
Effective SF6 gas storage and SF6/N2 mixture separations are extremely important in the industry. Herein, a series of isostructural metal-organic frameworks (MOFs), Cu6(H2O)3(NTB)4(PYZ)1.5 (SNNU-202, ...H3NTB = nitrilotribenzoic acid, PYZ = pyrazine), Cu12(H2O)3(NTB)8(PYZ)3(BPY)1.5 (SNNU-203, BPY = 4,4′-bipyridine) and Cu6(NTB)4(DABCO)1.5(BPY)1.5 (SNNU-204, DABCO = 1,4-diazabicyclo2.2.2octane), with different pore window sizes have been explored for the adsorption and separation performance of sulfur hexafluoride. With stepwise partitioning of the pore window, the adsorption capacity for SF6 and separation of SF6/N2 mixture are gradually improved. Notably, the SF6 uptake value for SNNU-204 is 6.0 mmol g−1 and the amount of substance ratio of SF6-to-N2 uptake can be up to 29.8 at 298 K and 1 bar, surpassing most of top-performing MOFs reported. Ideal adsorbed solution theory (IAST) calculations and breakthrough curves demonstrated that SNNU-204 exhibited excelling separation performance. The stepwise pore window partition can create more micropores, and the aromatic ring of the inserted ligand also facilitates interaction with sulfur hexafluoride gas molecules, providing an important strategy for the application of MOFs in SF6 gas adsorption and separation.
Pore window partitions through stepwise insertion the second or third ligands on the cage windows rationally regulate the interactions between metal-organic frameworks and sulfur hexafluoride molecules and endow with an high sulfur hexafluoride adsorption and high-efficient sulfur hexafluoride-nitrogen separation. Display omitted
•Different pore window sizes in Cu-MOFs affects the adsorption and separation of SF6.•Aromatic ring modified SNNU-204 shows excellent adsorption and separation of SF6.•The stepwise pore window partition strategy enables effective capture of SF6.
Graphene oxide (GO)-based nanofiltration membranes, featuring well-ordered microscopic structure, well-defined 2D nanochannels and superior molecular sieving ability, have attracted sustained ...research interest in molecular and ionic separation. However, most of current GO laminar membrane have a poor water flux and high rejection of both dyes and salts, which is not suitable for the dye/salt mixture separation. Herein, we report a vacuum filtration strategy to fabricate GO/NH2-Fe3O4 nanofiltration membranes with high water flux and excellent separation performance for dye/salts mixture by introducing NH2-Fe3O4. The NH2-Fe3O4 is not only worked as the rigid spherical nanospacer to tune GO interlayer spacing but also as crosslinkers to improve the stability of GO membrane in water. FTIR, XRD, SEM, zeta potential and contact angle were applied to analyze the chemical composition and morphology of as-prepared membranes. The effect of intercalated NH2-Fe3O4 nanoparticles on overall performance of the GO/NH2-Fe3O4 membranes was systematically investigated. The resulted membrane with 8 wt% of NH2-Fe3O4 loading has high water flux of up to 78 Lm−2 h−1, which is 4.8 times higher than that of pure GO membrane. Moreover, such membrane also displays high congo red rejection (94%) and low NaCl rejection (~15%), rendering the membranes promising for dye/salt mixtures separation.
Intercalated NH2-Fe3O4 can simultaneously tune the GO interlayer spacing and improve the stability of GO membrane in water. Display omitted
•GO/NH2-Fe3O4 membranes were prepared for dye/salt mixture separation.•NH2-Fe3O4 can simultaneously tune interlayer spacing and improve membrane stability.•GO/NH2-Fe3O4-8 membrane has high water flux and CR rejection but low NaCl rejection.
Using tubular kapok fibers (KF) and sodium alginate (SA) as the natural building block, we put forward a novel oriented neurovascular network-like superhydrophobic aerogel with robust dry and wet ...compression resilience by directional freeze-drying and chemical vapor deposition. In the block, SA forms aligned channel structures providing space for rapid oil transmission, while KF serves as vascular-like capillaries acting as instant “tentacle” to capture the tiny oil droplets in water, facilitating fascinating oil capture efficiency for versatile oil/water separation, The aerogel after dry and wet compression (under a strain of 60%) can recover 96.0% and 97.3% its original, respectively, facilitating stable oil recovery (81.1–89.8%) by squeezing, high separation efficiency (99.04–99.64%) and permeation flux separating oil contaminants from water. A pump-supported experiment shows the aerogel efficiently collecting oil contaminants from the water’s surface and bottom by 11503–25611 L·m−2·h−1. Particularly, the aerogel as robust oil droplets captor facilely achieves isolation of 99.39–99.68% emulsified oils from oil/water emulsions by novel oil trapping mechanism which simply involves exerting kinetic energy on emulsified oils through repeated oscillation, potentially indicating a simple and efficient alternative to membrane-based oily wastewater remediation via filtration.
Display omitted
•Novel oriented neurovascular network-like superhydrophobic aerogel was put forward.•Tubular kapok fibers and sodium alginate was used as the natural building block.•Both robust dry and wet compression resilience were demonstrated.•Facile gravity-driven oil/water separation and pump-driven consecutive oil recovery.•Facilely achieving isolation of 99.39–99.68% oils from oil-in-water emulsions.
Display omitted
•A hierarchical structured mesh decorated with UiO-66-NH2/GO was prepared.•The hierarchical structured mesh possessed super-hydrophilicity and underwater super-oleophobicity.•The ...hierarchical structured mesh exhibited outstanding antifouling performance.•The hierarchical structured mesh possessed super-high separation performance and recycling capacity.
A hierarchical structured steel mesh decorated with metal organic framework (UiO-66-NH2) nanoparticles/graphene oxide (GO) nanosheets was successfully prepared via a simple self-assemble method. Because water molecules tend to build hydrogen bonds with the amine, carboxyl and hydroxyl functional groups of UiO-66-NH2/GO hierarchical structure, the hierarchical structure can easily capture water and tightly lock the water to build a stable water layer on the steel mesh surface and block oil in contact with the steel mesh. Therefore, the obtained hierarchical structured steel mesh exhibits super-hydrophilicity, underwater super-oleophobicity, excellent oil resistance and outstanding oil/water separation performance with a superior high permeating flux (54,500 L m−2 h−1) and rejection (>99.9%) under gravity force, indicating the mesh possesses great potential for treating oily wastewater.
In the present work, three-Dimensional stationary numerical simulations were accomplished for a deeper understanding of the gas mixtures separation by the thermogravitational column. To address the ...optimum condition and examine the limitation of the process, the thermogravitational column behavior has been thoroughly analyzed. First, the simulation model was validated by the experimental results of Youssef et al. then the model was developed for the pilot column. The mixture of helium-argon was chosen as feed composition. It was concluded that the variation of the separation factor in relation to pressure for both columns was almost the same. The optimum condition verified as
A hyphenated technique combining FTIR Spectroscopy and Barometry is implemented to study transport properties of pure and mixed gases in rubbery polymers. FTIR spectroscopy is operated in situ and in ...the transmission mode. The specific case of transport of pure CO2 and CH4 in polydimethylsiloxane (PDMS) was addressed by performing the experimental investigation at ambient temperature and pressure values up to 9 bar, analyzing quantitatively both the gas phase and the solid polymer phase. The IR signals of each species in the gaseous phase were first calibrated against density data of each pure gas. Then, sorption experiments from a unary gas phase were conducted increasing the pressure stepwise and the amount of gas sorbed at each pressure within the polymer was quantitatively determined by measuring the absorbance decay within the gas phase. From these measurements, equilibrium sorption isotherms and sorption kinetics of both pure gases in PDMS have been evaluated. At the same time, FTIR spectra of pure CO2 absorbed within the polymer phase were collected and calibrated. The spectroscopic contrast in the gas and the polymer phase allowed us to apply the same approaches to sorption of gas mixtures, a very difficult task with the techniques currently available. Preliminary results for the sorption of carbon dioxide from CO2/CH4 gas mixtures are presented.
Display omitted
•FTIR Spectroscopy quantifies equilibrium sorption and mass transport properties.•Calibration is performed with an independent technique such as Barometry.•Spectra in both condensed and gas phase are collected and analyzed.•Extension to analysis of sorption of multicomponent mixtures is straightforward.•Swelling and transport properties measurements can be conducted simultaneously.
Reverse osmosis (RO) is a pressure driven membrane process which has been widely applied and recognized as the leading technology of desalination process. Improvement in RO technology including ...advanced membrane material, module and process design, and energy recovery has led to cost reduction which in turn gaining interest to its commercial applications. RO is now being used in various applications including selective separation, purification, and concentration processes. In food industry, RO is applied for concentration of fruits and vegetable juices, pre-concentration of milk and whey, and dealcoholization of alcoholic beverage. For area which has large source of natural humic water or peat water, RO can be applied to produce clean water for community water supply. RO was also investigated for organic mixture separation and CO2 regeneration from essential oil extraction using supercritical fluid. The application of RO as a final step of wastewater treatment for water reuse and valuable component recovery seems to be promising in wastewater reclamation. In this paper, the applications of RO, its advantages, and limitations are discussed. In addition, challenges and perspective of RO membranes are pointed out.
•Applications of reverse osmosis (RO) membrane are reviewed.•Advantages and limitations of the applications are discussed.•Challenges and perspective are pointed out.
