Inorganic Membranes Research Articles

Flexible, nonflammable and Li-dendrite resistant Na2Ti3O7 nanobelt-based separators for advanced Li storage

Li-dendrite resistant and high-performance separators are effective ways to solve the safety problem in advanced Li storage. Several intrinsic factors, including low thermal stability, low porosity and poor wettability, restrict the application of organic separators in safe Li storage. Inorganic porous membranes are promising candidates for commercial polyolefin-based separators due to their excellent thermal stability and good compatibility with organic electrolytes. In this study, we develop a flexible, Li-dendrite resistant and binder-free inorganic separator for safe Li storage based on ultralong Na2Ti3O7 nanobelts. The high thermal stability of Na2Ti3O7 nanobelts enables the separators to preserve their structural integrity up to 1000 °C. In addition, the as-prepared separators exhibit excellent flexibility, high porosity, and high cycling stability, which guarantee both the safety and high performance of the batteries.

Ultrathin Carbon Molecular Sieve Films and Room-Temperature Oxygen Functionalization for Gas-Sieving.

Inorganic membranes based on carbon molecular sieve (CMS) films hosting slit-like pores can yield high molecular selectivity with a sub-angstrom resolution in molecular differentiation and therefore are highly attractive for energy-efficient separations. However, the selective layer thickness of the state-of-the-art CMS membranes for gas separation is more than 1 μm, yielding low gas permeance. Also, there is no room-temperature functionalization route for the modification of the pore-size-distribution of CMS to increase the molecular selectivity. In this context, we report two novel fabrication routes, namely, transfer and masking techniques, leading to CMS films with thicknesses as small as 100 nm, yielding attractive gas-sieving performances with H2 permeance reaching up to 3060 gas permeation unit (GPU). Further, a rapid and highly tunable room-temperature ozone treatment-based postsynthetic modification is reported, shrinking the electron density gap in the nanopores by a fraction of an angstrom and improving gas selectivities by several folds. The optimized membranes yielded H2 permeance of 507 GPU and H2/CH4 selectivity of 50.7.

A Novel Metal–Organic Framework (MOF)–Mediated Interfacial Polymerization for Direct Deposition of Polyamide Layer on Ceramic Substrates for Nanofiltration

AbstractA facile metal–organic framework (MOF)‐mediated interfacial polymerization (IP) method is developed to prepare a polyamide (PA) layer directly on the ceramic substrate for nanofiltration. MOF is introduced to connect ceramic substrate and PA layer via chemical bonding, resulting in a robust separation layer. The optimization of IP can be controlled by MOF growth process via tuning the surface roughness as well as hydrophilicity. This method will provide a new way for the preparation of next generation of organic–inorganic composite membranes.

Techno-economic evaluation of helium recovery from natural gas; A comparison between inorganic and polymeric membrane technology

Natural gas produced at high pressure (50-70 bar) is the only industrial source of helium (He). A membrane separation process may offer a more efficient production system with smaller footprint and lower operational cost than conventional cryogenic system. Inorganic membranes with high mechanical strength are known to exhibit good stability at high pressure. In this work, two inorganic membranes, porous silica and carbon molecular sieve (CMS) were studied by simulation for their applicability in the He recovery process and compared against a Matrimid polymeric membrane. An in-house developed membrane simulation model (Chembrane) interfaced with Aspen HYSYS was used to simulate the membrane area and energy requirement for the He separation process. He was separated directly from a mixture containing methane (CH4) and 1-5 mole% He in the feed stream, and natural gas containing 1-5 mole% of He in a mixture of CH4 and N2. These streams were considered at 70 bar pressure and 25 °C. Single and two-stage membrane separation processes with and without recycle stream were simulated to achieve 97 mole % purity and 90% recovery of He. The simulation results showed that all three membranes can achieve required purity and recovery in a two-stage separation process. However, a recycle is required while using Matrimid membrane which adds cost and complexity to the system. The highest net present value (NPV) for silica, CMS, and Matrimid membrane was $M 2.5, 2, and 1.75 respectively when 5% He is present in feed gas and 15 years of plant life is considered.

Calcium removal from calcium rich paper mill wastewater by microbial CaCO3 precipitation

High concentrations of calcium present in paper mill wastewaters are considered as they lead to some important problems during the treatment process. Recently, submerged membrane bioreactor (sMBR) system have been commonly used to industrial wastewater treatment and it is observed that membrane scaling or fouling is one of the most important problems which causes many operational difficulties. A decrease in membrane flux is observed after the formation of CaCO3 film on the membrane surface as inorganic membrane fouling is encountered during the operation of the sMBR. Microbial carbonate precipitation (MCP) process is a natural microbial process and the mechanism of MCP is defined as the ability of microorganism to alkalinise an environment through various physiological activities. The purpose of this study was to investigate the application of MCP to paper-mill wastewater as a pre-treatment method prior to submerged membrane bioreactor. The potential for CaCO3 removal from wastewater through urea was investigated at optimum operation conditions obtained from the batch tests using a sequencing batch reactor (SBR). The optimum dosage of urea and HRT were determined 4 g/L and 72 h. The results obtained indicated that the calcium removal efficiency was found to be 90.16% at optimum experimental conditions in the SBR operation. It was found out that the MCP was a suitable method for calcium removal and it can be used as a pre-treatment method of paper-mill wastewater treatment to avoid calcium scaling and inorganic fouling in sMBR in the study.

Phosphorus-doped g-C3N4 integrated photocatalytic membrane reactor for wastewater treatment

Photocatalytic membrane reactors (PMRs) have been widely used in wastewater treatment over the past few years. In this study, P-doped g-C3N4 (PCN), a metal-free, visible light (Vis)-driven photocatalyst, was prepared and coated on an Al2O3 substrate followed by integration with an inorganic Al2O3 hollow fiber membrane module for use as a PMR. The 10 wt % of PCN exhibited the highest degradation activity for methyl blue (MB) removal under Vis irradiation because the C sites and vacancies within the heptazine rings of the CN units were substituted with P to improve charge separation and reduce the number of unpaired electrons. The PMR exhibits higher efficiency and stability in the removal of MB, methyl orange, phenol solution, and a mixture of the three organic compounds than do individual hollow fiber membranes or photocatalysis systems. The TOC (total organic carbon) analysis revealed that more than 92% of the phenol was decomposed and mineralized in the PMR, which also had a MB removal efficiency of greater than 90% when repeatedly used for four times. These results indicate that the PMR developed in this study is highly active and stable, and can serve as a promising system for effective removal of organic pollutants in wastewater.

Modeling Sulfur Poisoning of Palladium Membranes Used for Hydrogen Separation

Hydrocarbons are the most important source for hydrogen production. A combined reaction-separation process using inorganic membranes can significantly increase the reaction conversion by shifting the equilibrium toward product formation. Sulfur poisoning is a significant problem as it deactivates the most commonly used metallic membranes. The relationship of the membrane activity and surface coverage with the surface structure has been recognized in the literature. A theoretical model to simulate hydrogen transport in the presence of sulfur compounds is presented. This model accounts for active site deactivation and permanent structural damage to the membrane. Transport and reaction rate parameters used in the model have been estimated from experimental data. Qualitatively, the model represents well the behavior of inorganic membranes, including partial membrane activity regeneration after the sulfur source is removed.

Novel membrane percrystallisation process for nickel sulphate production

This research reports on an investigation of the performance of inorganic membranes for use in the percrystallisation of nickel sulphate hydrate. In this novel process, the separation of the solvent (water) and the crystallised solute (nickel sulphate hydrate) occurs continuously in a single-step, avoiding further downstream processing (crystal filtering and drying). The inorganic membranes were synthesised with sucrose solution followed by a post vacuum-assisted impregnation of the coated film on a α-alumina substrate and carbonisation under nitrogen atmosphere. The highest fluxes measured were 22 L m−2 h−1 and 1 kg m−2 h−1 (40 g L−1) for water and nickel respectively. Interestingly, the transport of solution through the membrane also affected the hydration state of the nickel sulphate, as well as the crystal type and shape. High water fluxes delivered pure nickel sulphate heptahydrate with elongated and laminar crystal particles (~200 μm). Lower water fluxes produced both heptahydrate and hexahydrate salts with approximately spherical particles (also ~200 μm). There a number of factors that influence the crystallisation reaction such as the rate of evaporation which affects water availability and the resultant temperature at the permeate side of the membrane. Finally, the activation energy for nickel sulphate crystallisation was estimated to be approximately 16 kJ mol−1 based on feed solution temperatures.

'Birth defects' of photosystem II make it highly susceptible to photodamage during chloroplast biogenesis.

High solar flux is known to diminish photosynthetic growth rates, reducing biomass productivity and lowering disease tolerance. Photosystem II (PSII) of plants is susceptible to photodamage (also known as photoinactivation) in strong light, resulting in severe loss of water oxidation capacity and destruction of the water-oxidizing complex (WOC). The repair of damaged PSIIs comes at a high energy cost and requires de novo biosynthesis of damaged PSII subunits, reassembly of the WOC inorganic cofactors and membrane remodeling. Employing membrane-inlet mass spectrometry and O2 -polarography under flashing light conditions, we demonstrate that newly synthesized PSII complexes are far more susceptible to photodamage than are mature PSII complexes. We examined these 'PSII birth defects' in barley seedlings and plastids (etiochloroplasts and chloroplasts) isolated at various times during de-etiolation as chloroplast development begins and matures in synchronization with thylakoid membrane biogenesis and grana membrane formation. We show that the degree of PSII photodamage decreases simultaneously with biogenesis of the PSII turnover efficiency measured by O2 -polarography, and with grana membrane stacking, as determined by electron microscopy. Our data from fluorescence, QB -inhibitor binding, and thermoluminescence studies indicate that the decline of the high-light susceptibility of PSII to photodamage is coincident with appearance of electron transfer capability QA - → QB during de-etiolation. This rate depends in turn on the downstream clearing of electrons upon buildup of the complete linear electron transfer chain and the formation of stacked grana membranes capable of longer-range energy transfer.

Bioinspired Modification of Layer-Stacked Molybdenum Disulfide (MoS2) Membranes for Enhanced Nanofiltration Performance.

Inorganic nanofiltration membranes with high flux are urgently needed in water purification processes. Herein, polydopamine (PDA)-modified layer-stacked molybdenum disulfide (MoS2) nanofiltration membranes (NFMs) were fabricated via a pressure-assisted self-assembly process. The separation performance of the as-prepared membranes with various MoS2 loadings at different dopamine polymerization times was evaluated. The pure water permeance of PDA-modified MoS2 NFMs, with MoS2 loading of 0.1103 mg/cm2 at 4 h modification, could reach 135.3 LMH/bar. The rejection toward methylene blue could reach 100% with molecular weight cutoff approximately 671 Da and a high permeability of salts. Furthermore, the resultant membrane also exhibited a satisfactory long-term stability toward dye solution and antifouling property toward bovine serum albumin. This work may give inspiration to the development of inorganic membranes with high performance, especially high pure water permeance, for water-related processes.

Recent developments on catalytic membrane for gas cleaning

Abstract Catalytic membrane, a novel membrane separation technology that combines catalysis and separation, exhibits significant potential in gas purification such as formaldehyde, toluene and nitrogen oxides (NOx). The catalytic membrane can remove solid particles through membrane separation and degrade gaseous pollutants to clean gas via a catalytic reaction to achieve green emissions. In this review, we discussed the recent developments of catalytic membranes from two aspects: preparation of catalytic membrane and its application in gas cleaning. Catalytic membranes are divided into organic catalytic membranes and inorganic catalytic membranes depending on the substrate materials. The organic catalytic membranes which are used for low temperature operation (less than 300 °C) are prepared by modifying the polymers or doping catalytic components into the polymers through coating, grafting, or in situ growth of catalysts on polymeric membrane. Inorganic catalytic membranes are used at higher temperature (higher than 500 °C). The catalyst and inorganic membrane can be integrated through conventional deposition methods, such as chemical (physical) vapor deposition and wet chemical deposition. The application progress of catalytic membrane is focused on purifying indoor air and industrial exhaust to remove formaldehyde, toluene, NOx and PM2.5, which are also summarized. Perspectives on the future developments of the catalytic membranes are provided in terms of material manufacturing and process optimization.

Sustainability considerations in membrane-based technologies for industrial effluents treatment

Treatment of industrial effluents (EFs) from the polluted wastewater sources using membrane technologies is an effective and attractive alternative to overcome the weaknesses of some of the conventional wastewater treatment processes, especially when dealing with EFs loaded with recalcitrant organic pollutants and toxic substances. The application of various polymeric and inorganic membrane based technologies to be used for the treatment of industrial EFs has attracted a considerable attention in the past decades. In this regard, a critical discussion on the sustainability of various aspects of membrane technologies would promote the commercialization of these technologies. In this review, various sustainability criteria in technical, economic, environmental, and social categories have been considered for a critical discussion on the current status and improvement opportunities of membrane technologies for the treatment of industrial EFs. While the application of polymeric membranes has been restricted by some bottlenecks to deal with some industrial effluents, metal oxides fabricated ceramic membranes, and especially those fabricated with nanostructured materials such as nano-zeolites, those made of metal organic frameworks as well as carbon-based fabricated membranes have shown a promising performance in the rejection of recalcitrant organic pollutants. In addition, the combinations of inorganic membrane technologies with other novel methods such as advanced oxidation processes (e.g., using engineered nanomaterials) can be considered among the best options to deal with such highly polluted effluents.

The condensation behaviours of carbon dioxide on MgO surface

Various separation methods for carbon dioxide gas have been proposed to control its release to the atmosphere, including the separation using an inorganic membranes such as ceramic MgO. In this work, molecular dynamics simulations are performed to clarify the condensation behaviour of carbon dioxide, in its pure and mixture state, onto the surface of MgO at a high operational temperature. The results show that no condensation of pure carbon dioxide is observed on MgO surface. However, the presence of methane impurity can promote the condensation of carbon dioxide on MgO surface as a single layer with an ordered configuration.

Synthesis and properties of sulfonated poly(arylene ether ketone sulfone) containing amino groups/functional titania inorganic particles hybrid membranes for fuel cells

In this work, the organic-inorganic hybrid membranes were prepared. The synthesis and properties of the hybrid membranes were investigated. The sulfonated poly(arylene ether ketone sulfone) containing amino groups (Am-SPAEKS) was synthesized by nucleophilic polycondensation. The sol-gel method was used to prepared functional titania inorganic particles (L-TiO2). The 1H NMR and FT-IR were performed to verified the structure of Am-SPAEKS and L-TiO2. The organic-inorganic hybrid membranes showed both good thermal stabilities and mechanical properties than that of Am-SPAEKS. The L-Am-15% membrane exhibited the highest Young's modulus (2262.71 MPa) and Yield stress (62.09 MPa). The distribution of L-TiO2 particles was revealed by SEM. Compared to Am-SPAEKS, the hybrid membranes showed higher proton conductivities. The L-Am-15% exhibited the highest proton conductivity of 0.0879 S cm−1 at 90 °C. The results indicate that the organic-inorganic hybrid membranes have potential for application in proton exchange membrane fuel cells.

Superhydrophobic or Hydrophilic Porous Metallic/Ceramic Tubular Membranes for Continuous Separations of Biodiesel–Water W/O and O/W Emulsions

This paper reports the effective surface effect of porous inorganic membranes on improving the emulsion separations (i.e., perm-selective extraction of either oil phase or aqueous phase from the emulsions). A novel tubular form of superwetting, porous, stainless steel/ceramic membranes were demonstrated for enabling continuous separations of oil–water emulsions, extracting either oil phase or aqueous phase from the flowing emulsions. The superhydrophobic membranes consist of macroporous (4 μm) stainless-steel SS434 tube with inner wall surface modified with superhydrophobicity (>150° contact angle) via perfluoro-silane grafting functionalization. The (super)hydrophilic membranes consist of 4-μm porous stainless-steel SS434 tube without/with inner wall coated with nanoporous alumina (6 nm average pore size), the surface of which was further modified with superhydrophilicity via Hydrophil-S solution deposition. With the cross-flow membrane filtration setup, the surface-engineered tubular membranes were stud...

Composite inorganic anion exchange membrane for electrodialytic desalination of milky whey

Composite membranes have been obtained by modification of macroporous ceramics with hydrated zirconium dioxide and basic bismuth nitrate. The modification technique provided formation of the two-component modifier directly in macropores of the inorganic matrix. This method allows us to obtain the material, which possesses by optimal combination of charge selectivity and electrical conductivity, by means of one-time modification. It is assumed that nanoparticles of basic bismuth nitrate (5 nm) block pores between larger particles of hydrated zirconium dioxide (several tens of nanometers) providing semipermeability of the membranes towards anions in acidic media: potentiometric transport number of counter-ions (Cl-) reaches 0.9. Electrodialytic desalination of milky whey has been carried out using a pair of polymer cation exchange (Nafion 117) and composite inorganic membranes. The possibility of whey desalination under overlimiting current has been shown. The current efficiency due to anions reaches 80% under these conditions. Electrodialysis of whey allows us to remove 75 % of the mineral components in 3 h, the same purification degree is achieved in 30 min for nanofiltration permeate.

Highly flexible, mesoporous structured, and metallic Cu-doped C/SiO2 nanofibrous membranes for efficient catalytic oxidative elimination of antibiotic pollutants.

The development of inorganic membranous catalysts with both large mesopores and superb flexibility is extremely favorable for the enhancement of their catalytic oxidation activity for the degradation of antibiotic pollutants in wastewater via sulfate radical-based advanced oxidation processes; however, there still exists a huge challenge for inorganic materials to simultaneously realize these two properties. Herein, metallic copper-doped carbon/silica nanofibrous membranes (Cu@C/SiO2 NFMs) with large mesopores, superb flexibility, and robust mechanical strength were fabricated through a sol-gel electrospinning and subsequent in situ carbonization reduction method. The synthesized Cu nanoparticles were homogeneously distributed throughout the mesoporous C/SiO2 nanofiber matrix, which enabled the resultant Cu@C/SiO2 NFMs to be applied as heterogeneous catalysts, and their catalytic performance was systematically assessed through activating persulfate for the elimination of tetracycline hydrochloride (TCH) in water. The fabricated Cu@C/SiO2 NFMs provided outstanding catalytic performance towards TCH with a high removal efficiency of 95% in 40 min and a rapid removal speed of 0.054 min-1. Moreover, the membranes could be facilely recycled through being directly separated from water without any post-processing. Such a facile strategy for preparing mesoporous and flexible metal-doped inorganic nanofibrous membranes may offer novel insights for designing new types of heterogeneous catalysts for antibiotic-containing wastewater treatment or other potential applications.

Self-repairing mechanism and surface characterization of compressor vanes lubricated with oil added with magnesium silicate hydroxide nanorods

Using magnesium silicate hydroxide as additive of lubricating oils for reducing friction in engineering equipment/machinery has been researched intensively. However, some mechanism relating to the growth of the self-repairing layers on the won surfaces is still not clearly explained. At the same time, using magnesium silicate hydroxide (MSH) in the form of nanorods showed great promise in reducing friction and wear. In this study, surface-modified MSH in the form of nanorods was used as additive of polyolester oil (POE) which was then used for the lubrication of compressor vanes. The sample parts were studied on the morphology and the microstructure of the self-repairing layer in a great depth. The results showed that self-repairing layers with different thicknesses were generated on the worn surfaces when the POE with 1 wt.% nanorods-MSH was used. It was found that the self-repairing layers consist of organic–inorganic composite membranes, and with increase of working time of the compressor vanes, the self-repairing layers become denser and thicker, while their micro-structural form remains to be similar. The situ-repairing capability of the metal surfaces (roller-vane pair of the compressor) enforced by the MSH nanorods is very significant, indicating high potential for industrial applications where boundary and mixed lubrications are needed.

Dual-Layer MOF Composite Membranes with Rationally Tuned Interface Interaction for Post-Combustion CO <sub>2</sub> Separation

A novel concept for the fabrication of dual-layer metal organic framework (MOF) membranes is presented herein that show great promise in improving permeability and selectivity performance for CO2/N2 separation as compared with the individual constituent MOF materials. A highly selective thin MOF layer with narrow pore size was grown on the surface of a highly permeable MOF layer with large pore size. Most importantly, chemical binding at the interface between the two MOF layers made it possible to achieve continuous, defect-free membranes. The two dual-layer MOF@MOF membranes: SIFISIX-3-Ni@SIFISIX-1-Cu and SIFISIX-3-Ni@HKUST-1, represent the first examples of pure inorganic membranes constructed from dual-layer MOF composites. The CO2/N2 selectivities of the HKUST-1 and SIFSIX-1-Cu membranes were improved from 5.2 to 13.0 and 3.4 to 7.8, respectively, after the growth of a selective layer of SIFSIX-3-Ni onto the surface of those materials.

Novel nanocomposite polyethersulfone- antimony tin oxide membrane with enhanced thermal, electrical and antifouling properties

Application of organic−inorganic nanocomposite membranes for water treatment is exceptionally growing owing to their tunable functionalities in addition to their enhanced permeation and antifouling propensity. In the present work, novel nanocomposite polyethersulfone (PES) membrane was synthesized using antimony-doped tin oxide (ATO) nanoparticles (NPs) via phase separation technique. It was found that the modified PES-ATO nanocomposite membranes exhibited significantly higher fouling resistance and larger permeate flux recovery ratio when tested with oil sands produced water than unmodified PES membranes. Furthermore, the PES-ATO membranes provided 40% more organic matter removal compared to the base PES membranes. However, the addition of the ATO NPs to the PES casting solution resulted in tighter membranes with denser skin layer and lower average pore size. By evaluation of the surface potential and wettability of the membrane, it was revealed that the higher antifouling propensity and larger separation efficiency of the nanocomposite membrane originate primarily from their higher surface hydrophilicity and lower porosity which resulted in about 99% flux recovery during the filtration of oil sands produced water. Furthermore, the developed PES-ATO nanocomposite membranes demonstrated larger electrical conductivity and higher thermal stability compared to pristine PES membranes. The tunable antifouling propensity along with enhanced thermal stability and electrical conductivity suggest the promising potential of the developed PES-ATO nanocomposite membrane to be employed in advanced membrane technologies using external stimuli such as electric field, or thermal gradient for the purification of industrial produced water.