Ideal Pore Size Research Articles

Effects of Preformed Composition and Pore Size on Microstructure and Properties of SiCf/SiC Composites via Reactive Melt Infiltration

This study investigated the influence of preformed composition and pore size on the microstructure and properties of SiCf/SiC composites fabricated via reactive melt infiltration (RMI). The process began with the impregnation of SiC fiber cloth with phenolic resin, followed by lamination and pyrolysis. Subsequent steps included further impregnations with phenolic resin, SiC slurry, and carbon black slurry, each followed by additional pyrolysis. This process resulted in three types of preforms, designated as PP, PS, and PC. These preforms exhibited a multimodal distribution of pore size, with peak pore diameters around 5 μm for PP, ranging from 200 nm to 4 μm for PS, and approximately 150 nm for PC. The preforms were then subjected to molten silicon infiltration at 1600 °C under vacuum for 1 h to create SiCf/SiC composites. The PP preform contained only pyrolytic carbon, leading to a composite with high closed porosity and unreacted carbon, resulting in poor mechanical properties. The PS preform, which was impregnated with SiC particles, displayed an optimized pore size distribution but retained significant amounts of residual silicon and carbon in the final composite. In contrast, the PC preform featured both an ideal pore size distribution and an adequate amount of carbon, achieving high density and low porosity with reduced residual phases in the final composite. This optimization led to a flexural strength of 152.4 ± 15.4 MPa, an elastic modulus of about 181.1 ± 0.1 GPa, and a thermal conductivity of 27.7 W/mK in the SiCf/SiC composites product. These findings underscore the importance of preform optimization in enhancing the performance of SiCf/SiC composites, potentially paving the way for more reliable nuclear fuel cladding solutions.

Revving Up a Designed Copper Catecholate Porous Organic Polymer for Its Potent Ethylene Adsorption than Ethane.

The potential to produce high-purity C2H4 has made ethylene-selective adsorbents for ethane (C2H6)/ethylene (C2H4) gas mixture separation appealing as viable substitutes for traditional cryogenic distillation. In this aspect, porous organic polymers (POPs) are anticipated to become the next-generation potential adsorbent due to their easily customizable functions and functional sites suitable for gas separation. This article reports the selective C2H4 adsorption over C2H6 using microporous copper(I)-coordinated POP (Cu@Di-POP) via fine-tuning of the π complexation and pore size. The specially designed adsorbent has the ideal pore size and coordinated Cu(I) ions to form π-complexation with C2H4 molecules, which enabled it to adsorb C2H4 (at 1 bar, 24.9, 18.9, and 13.4 cm3 g-1 at 273, 298, and 323 K, respectively) while significantly reducing C2H6 adsorption (at 1 bar, 16.9, 12.7, and 8.8 cm3 g-1 at 273, 298, and 323 K, respectively). At 1 bar, Cu@Di-POP exhibited IAST selectivities of 6.09, 5.60, and 4.13 for C2H4/C2H6 at 273, 298, and 323 K, respectively, suggesting its C2H4 selective behavior, which was further confirmed from the experimental breakthrough measurement. Furthermore, the computational studies carried out with density functional theory highlighted an enhanced charge distribution leading to dπ-pπ conjugation between C2H4 π-electrons and Cu d-electrons, thereby showing a relatively higher interaction energy of -37.23 kcal/mol with C2H4 as compared to -16.06 kcal/mol with C2H6 gas molecules.

Europium-Doped 3D Dimensional Porous Calcium Phosphate Scaffolds as a Strategy for Facilitating the Comprehensive Regeneration of Bone Tissue: In Vitro and In Vivo.

In response to the challenges faced by clinicians treating bone defects caused by various factors, various bone repair materials have been investigated, but the efficiency of bone healing still needs to be improved due to the acting of scaffolds only in a single stage of bone tissue regeneration. We investigated the potential of a novel 3D scaffold to support different stages of bone tissue regeneration, including initial inflammation, proliferation, and remodeling. Eu (0, 0.5, 2, 3.5, 5, and 6.5%) was added to calcium polyphosphate to obtain 3D porous network-doped Eu calcium polyphosphate (EuCPP) scaffolds with ideal mechanical strength and pore size. Both in vitro and in vivo experiments proved that Eu3+ released from 5% EuCPP scaffolds could significantly promote the migration and proliferation of bone marrow stromal cells which effectively promote angiogenesis; 5% EuCPP could significantly upregulate the ratio of OPG/RANKL in MC3T3-E1 and promote the secretion of osteogenic-related growth factors (ALP and OPN) from MC3T3-E1, indicating the potential of the scaffold to inhibit bone resorption and promote bone formation. In conclusion, 5% EuCPP possesses the biological properties of pro-angiogenesis, anti-inflammation, pro-osteogenesis, and inhibiting bone resorption, which may provide a sustained positive effect throughout the process of bone tissue repair.

Акустические характеристики пористого алюминия, применяемого для изготовления шумопоглощающих устройств промышленного оборудования

Noise-absorbing devices made of porous aluminum have been used as components of units and systems of modern industrial equipment (pressure regulators, compressors, exhaust systems, pneumatic tools, heat engines, etc.). The advantages of products made of the material are high mechanical strength, resistance to chemicals, vibrational and thermal loads, and recyclability. Noise absorption in the structure of porous aluminum is caused by the loss of energy as a result of viscous friction and heat exchange between oscillating air particles and the skeleton of the material. Structural parameters of porous metals significantly affect the efficiency of noise absorption. Experimental studies of sound-absorbing properties of porous aluminum samples of different thicknesses, porosity, and pore sizes have been carried out for the present paper. An acoustic impedance tube, in compliance with the requirements of ISO 10534 and ASTM E1050 on 5–20 mm thick samples, has been used for the study. The porosity of samples was 0.5–0.7, whereas the average pore size was equal to 0.6–2 mm. Two variants of sample installation have been investigated, i.e., without an air gap and with the formation of a 20 mm air gap relative to the surface of the rigid piston of the impedance tube. The impact of structural parameters and thickness of porous aluminum samples on their noise-absorption properties has been assessed based on the results of the study. It has been determined that the increase of average pore size within the range between 0.6 and 2 mm causes the reduction of the noise-absorption coefficient. The effect becomes more pronounced when a sample with the formation of an air gap relative to the piston surface is installed. With identical average pore sizes and thicknesses, the highest values of sound absorption coefficient by the porous aluminum samples have been registered for a porosity of 0.6. The study results can be used for the development and modernization of sound-absorbing devices for industrial equipment made of porous aluminum.

Impacts of permeability and effective diffusivity of porous scaffolds on bone ingrowth: In silico and in vivo analyses

The permeability and the effective diffusivity of a porous scaffold are critical in the bone-ingrowth process. However, design guidelines for porous structures are still lacking due to inadequate understanding of the complex physiological processes involved. In this study, a model integrating the fundamental biological processes of bone regeneration was constructed to investigate the roles of permeability and effective diffusivity in regulating bone deposition in scaffolds. The in silico analysis results were confirmed in vivo by examining bone depositions in three diamond lattice scaffolds manufactured using selective laser melting. The findings show that the scaffolds with better permeability and effective diffusivity had deeper bone ingrowth and greater bone volume. Compared to permeability, effective diffusivity exhibited greater sensitivity to the orientation of porous structures, and bone ingrowth was deeper in the directions with higher effective diffusivity in spite of identical pore size. A 4.8-fold increase in permeability and a 1.6-fold increase in effective diffusivity by changing the porous structure led to a 1.5-fold increase in newly formed bone. The effective diffusivity of the porous scaffold affects the distribution of osteogenic growth factor, which in turn impacts cell migration and bone deposition through chemotaxis effects. Therefore, effective diffusivity may be a more suitable indicator for porous scaffolds because our study shows changes in this parameter determine changes in bone distribution and bone volume.

Capture of carbonyl sulfide trace from natural gas by adsorption on zeolitic Nanostructure: Monte Carlo molecular simulation

The economic and environmental challenge for the oil and gas industries is to eliminate carbonyl sulfide (COS) from natural gas selectively. This compound can lead to corrosion and environmental damage, even when it is present in small amounts. The zeolites have been known as the appropriate adsorbent for COS. Grand Canonical Monte Carlo (GCMC) simulation has been used to explore the suitability of zeolite frameworks with different topologies on the adsorption and separation properties of mixtures containing industrial concentrations of COS in order to overcome the experimental tests that are difficult to handle. The adsorption isotherms for pure COS and COS/methane mixture on purely siliceous zeolites such as BEA, FAU, LTL, MFI, and MOR have been recorded at 298 K within a pressure range of 0–100 kPa. MFI zeolite, with its high adsorption capacity and isosteric heat, has been identified as the most suitable candidate for COS adsorption due to its ideal pore size and shape. Examining the density distribution snapshots reveals the preferred locations of zeolites for the COS adsorption. The findings could be systematically used in various case studies, thereby providing insights into selecting the best zeolitic nanostructure for the industrial removal processes of COS.

Advancing 3D Dental Implant Finite Element Analysis: Incorporating Biomimetic Trabecular Bone with Varied Pore Sizes in Voronoi Lattices.

The human mandible's cancellous bone, which is characterized by its unique porosity and directional sensitivity to external forces, is crucial for sustaining biting stress. Traditional computer- aided design (CAD) models fail to fully represent the bone's anisotropic structure and thus depend on simple isotropic assumptions. For our research, we use the latest versions of nTOP 4.17.3 and Creo Parametric 8.0 software to make biomimetic Voronoi lattice models that accurately reflect the complex geometry and mechanical properties of trabecular bone. The porosity of human cancellous bone is accurately modeled in this work using biomimetic Voronoi lattice models. The porosities range from 70% to 95%, which can be achieved by changing the pore sizes to 1.0 mm, 1.5 mm, 2.0 mm, and 2.5 mm. Finite element analysis (FEA) was used to examine the displacements, stresses, and strains acting on dental implants with a buttress thread, abutment, retaining screw, and biting load surface. The results show that the Voronoi model accurately depicts the complex anatomy of the trabecular bone in the human jaw, compared to standard solid block models. The ideal pore size for biomimetic Voronoi lattice trabecular bone models is 2 mm, taking in to account both the von Mises stress distribution over the dental implant, screw retention, cortical bone, cancellous bone, and micromotions. This pore size displayed balanced performance by successfully matching natural bone's mechanical characteristics. Advanced FEA improves the biomechanical understanding of how bones and implants interact by creating more accurate models of biological problems and dynamic loading situations. This makes biomechanical engineering better.

One-step sintering process for high-performance SiC membranes for efficient filtration of dust-laden gas

Silicon carbide (SiC) ceramic membranes are known for their remarkable attributes, including resistance to acid and alkali corrosion, exceptional tolerance to thermal shock, and high mechanical strength. These properties have garnered considerable attention for dust-laden gas filtration. However, large-scale applications of SiC membranes are limited because of the high sintering energy consumption in membrane formation. In this study, a preparation method for high-performance and low-cost SiC membranes using a co-sintering process was proposed. In this method, SiC particles with a 100-μm average particle size were uniformly mixed with sintering aids and SiC green supports were prepared via a dry pressing process. Subsequently, SiC dispersion was coated on the SiC green supports via a spray coating method to prepare membrane layer. Through optimization of the sintering process and sintering atmosphere, the sintering stress difference during co-sintering was released. Finally, a defect-free membrane surface was fabricated. The carbon powder in the green supports was utilized as a pore-forming agent and to prevent small particles in the SiC membrane layers from infiltrating the SiC green supports, decreasing the mass transfer resistance in the application process. The SiC ceramic membrane had a mean pore size and a gas permeance of 3.90 μm and 246.33 m3 m−2 h−1. In addition, when subjected to identical average pore size and porosity conditions, it exhibited a high Darcy's permeability coefficient, indicating favorable structural characteristics for the membrane. Additionally, the membrane was optimized to have a 99.9 % rejection of solid particles in dusty gases, including nanometer (0.3 μm) and micron (2.5 μm) solid particles. This study has introduced a preparation method for low-cost and high-performance SiC membranes for industrial dust-laden gas filtration.

Permeable and antifouling PSf‐Cys‐CuO ultrafiltration membrane for separation of biological macromolecules proteins

AbstractMembrane technology has been extensively applied for protein separation. A membrane with reliable filtration performance and high removal efficiency is required. In this study, an ultrafiltration (UF) membrane was fabricated by dry‐wet phase inversion to incorporate copper oxide nanoparticles (CuO NPs) with a different ratio of L‐cysteine (Cys) in polysulfone (PSf). The characterization of the membrane involves using scanning electron microscopy (SEM), water contact angle, water content, pore size, and porosity analysis. The membrane performance evaluation includes flux permeation and bovine serum albumin (BSA) removal as a protein foulant. The membrane antifouling feature was examined by dynamic filtration of BSA. It was found that the Cys to CuO NPs ratio of 1.7:1 gives an optimal value on flux permeation and protein removal. The membrane exhibited high removal of BSA with 96.3%, and optimum water flux was achieved at 173.3 L/m2h, respectively. The highest permeability of aqueous BSA permeate at 500 ppm was about 111 L/m2h and 82.5 L/m2h for 1000 ppm. The enhancement of PSf‐Cys‐CuO membrane performance could be due to its lower contact angle (68.7°), high porosity (68%), and ideal pore size (46 nm) as well as showing good morphological structure. Most significantly, the inclusion of Cys improves antifouling capabilities. The membrane showed a lower chance of fouling based on the evaluation of the relative flux reduction and flux recovery ratio. Hence, the availability of Cys has a better impact on the polymer‐based membrane and seems promising for protein separation applications.

Axial tension/compression and torsional loading of diamond and gyroid lattice structures for biomedical implants: Simulation and experiment

Lattice structures are increasingly used in biomedical implants, notably intervertebral cages, requiring a better understanding of their behavior for the different types of loading they undergo during application. Strut-based diamond and sheet-based gyroid structures with porosity levels ranging from 50 to 80 % and an identical pore size of 750 μm were manufactured from Ti6Al4V alloy, tested experimentally and simulated numerically in axial tension/compression and in torsion to simulate flexion/extension, compression and rotation of the human spine. The manufactured structures were within 5 % of the targeted porosity. However, numerical simulations overestimated the experimental apparent (effective) stiffness and strength of the structures by an average of 25 %, likely due to the presence in them of manufacturing defects, especially in the higher porosity lattices. Experimental and numerical results showed that the structures have quasi-identical mechanical properties in compression and in tension. However, a comparison of the torsion and axial results indicated that conventional bulk material failure theories such as the von Mises limitation criterion do not apply to the apparent properties of lattice structures. Studied lattices exhibited adequate resistance for use in intervertebral cages, however their stiffness was greater than those of the vertebrae, while situated in the stiffness range of cortical bone.

Effects of Porous Size and Membrane Pattern on Shear Stress Characteristic in Gut-on-a-Chip with Peristalsis Motion.

Dynamic gut-on-a-chip platform allows better recreation of the intestinal environment in vitro compared to the traditional static cell culture. However, the underlying mechanism is still not fully discovered. In this study, the shear stress behavior in a gut-on-a-chip device with porous membrane subjected to peristalsis motion is numerically investigated using CFD simulation for three different pore sizes and two pattern layouts. The results reveal that, in the stationary microchannel, the average shear stress on the porous membrane is approximately 15% greater than that of the flat membrane, regardless of the pore size. However, when subjected to cyclic deformation, the porous membrane with smaller pore size experiences stronger variation of shear stress which is ±5.61%, ±10.12% and ±34.45% from its average for the pore diameters of 10 μm, 5 μm and 1 μm, respectively. The shear stress distribution is more consistent in case of the staggered pattern layout while the in-line pattern layout allows for a 32% wider range of shear stress at the identical pore size during a cyclic deformation. These changes in the shear stress caused by peristalsis motion, porous size and membrane pattern could be the key factors that promote cell differentiation in the deforming gut-on-a-chip model.

Physico-biological evaluation of 3D printed dECM/TOCN/alginate hydrogel based scaffolds for cartilage tissue regeneration

Cartilage damage is the leading cause of osteoarthritis (OA), especially in an aging society. Mimicking the native cartilage microenvironment for chondrogenic differentiation along with constructing a stable and controlled architectural scaffold is considerably challenging. In this study, three-dimensional (3D) printed scaffolds using tempo-oxidized cellulose nanofiber (TOCN), decellularized extracellular matrix (dECM), and sodium alginate (SA) were fabricated for cartilage tissue regeneration. We prepared three groups (dECM80, dECM50, dECM20) of 3D printable hydrogels with different ratios of TOCN and dECM where SA concentration remained the same. Two-step crosslinking was performed with CaCl2 solution to achieve the highly stable 3D printed scaffolds. Finally, the fundamental physical characterizations showed that increasing the ratio of TOCN with dECM significantly improved the viscoelastic behaviour, stability, mechanical properties, and printability of the scaffolds. Based on the results, the 3D printed dECM50 scaffolds with controlled and identical pore sizes increased the whole-layer integrity and nutrient supply in each layer of the scaffold. Furthermore, evaluation of in vitro and in vivo biocompatibility of the scaffolds with rBMSCs indicated that dECM50 scaffolds provided a suitable microenvironment for cell proliferation and promoted chondrogenesis by remarkably expressing the cartilage-specific markers. This study demonstrates that 3D printed dECM50 scaffolds provide a favourable and promising microenvironment for cartilage tissue regeneration.

ZSM-5 Catalysts for MTO: Effect and Optimization of the Tetrapropylammonium Hydroxide Concentration on Synthesis and Performance

Light olefin production from methanol using various zeolite catalysts has industrial and economic importance considering the growth of the petrochemical market. Zeolites are generally synthesized using various organic templates as structure-directing agents (SDAs). In this study, synthesis of a series of ZSM-5 zeolites was performed systematically using the microwave-assisted crystallization method, and these samples were analyzed in detail to understand the effect of the SDA concentration. Powder diffraction, N2 adsorption, scanning electron microscopy, ammonia adsorption desorption, and 27Al and 29Si NMR spectroscopies were used for the characterization. The organic SDA tetrapropyl ammonium hydroxide (TPAOH/SiO2 mole ratio = 0.0500) is found to have an optimum concentration against the silica precursor for achieving the highest crystallinity, suitable morphology, ideal pore size, effective pore volume, and tuned microporous/mesoporous area. For samples with a template concentration ratio of 0.050 or higher, 29Si and 27Al NMR data revealed the presence of an intact ZSM-5 structure. Using a fixed bed reactor at 500 °C and atmospheric pressure, the catalytic performance of the selected catalysts from the series is investigated for the methanol-to-olefin conversion reaction. The sample with the highest crystallinity showed the best conversion, selectivity toward light olefins, and time on stream stability. It is also worth noting that the highest crystallinity, micropore area, and micropore volume are reached for the optimum value rather than the highest template concentration. This allows for a reduction in the template concentration and a move closer to a synthesis pathway benign to environment and economics.

An Environmentally Friendly Approach for the Synthesis of Au Nanoparticles Supported Mesoporous Silica for Catalytic Applications

Mesoporous silica has received much attention as an attractive support material for metal nanoparticles (NPs) with good dispersion and exceptional stability for various catalytic reactions. However, the lack of synthetic protocols to controlled synthesis of mesoporous silica with high surface area and ideal pore size for supporting metal NPs significantly reduces the catalytic performance and stability of the catalysts. This work reports a facile synthetic route to prepare mesoporous silica-supported Au NPs (Au/SiO2) for efficient catalytic reduction of 4-nitrophenol. An environmentally friendly synthetic route was exploited to prepare mesoporous silica using deep eutectic solvent (DES) derived from choline chloride/urea as an efficient solvent and template in solvothermal reaction. The mesoporous silica was first functionalized with –NH2 groups, and subsequently, Au NPs with an average size of 10 nm were deposited onto the mesoporous silica matrix. Owing to the strong interaction of supported Au NPs with the mesoporous silica support, the resultant composite exhibited excellent catalytic performance towards the reduction of 4-NP to 4-aminophenol with a rate constant of Kapp= 3.04 x10-1 min-1 and exceptionally high stability compared to bare mesoporous silica catalyst. The current green approach to fabricating mesoporous silica and Au/SiO2 catalysts holds great promise since it is a much cheaper and environmentally friendly method for large-scale fabrication of other supported catalysts for different catalytic reactions.

Bifunctionalized Metal–Organic Frameworks for Pore‐Size‐Dependent Enantioselective Sensing

AbstractPorosity is a fundamental property of metal–organic frameworks (MOFs). However, the role of the pore size has always been underestimated in MOF‐based luminescent sensors for enantioselective sensing. The construction of isoreticular MOFs (IRMOFs) with variable pore sizes and the synergy between chirality and luminescence is challenging. Herein, a general strategy was developed to introduce chirality into two well‐known IRMOF‐74 analogs with nanochannels of identical shapes but different pore sizes by functionalizing the open metal site under mild conditions. To enhance the detection accuracy, a second luminescent center was introduced into the IRMOF‐74 system to achieve ratiometric sensing. The two bifunctionalized IRMOF‐74 compounds exhibited pore‐size‐dependent sensing performance for enantiomers. This study not only provides a convenient method to construct chiral MOFs as advanced sensing materials but also reveals the fundamental of the pores in MOF‐based luminescent sensors.

Bifunctionalized Metal-Organic Frameworks for Pore-Size-Dependent Enantioselective Sensing.

Porosity is a fundamental property of metal-organic frameworks (MOFs). However, the role of the pore size has always been underestimated in MOF-based luminescent sensors for enantioselective sensing. The construction of isoreticular MOFs (IRMOFs) with variable pore sizes and the synergy between chirality and luminescence is challenging. Herein, a general strategy was developed to introduce chirality into two well-known IRMOF-74 analogs with nanochannels of identical shapes but different pore sizes by functionalizing the open metal site under mild conditions. To enhance the detection accuracy, a second luminescent center was introduced into the IRMOF-74 system to achieve ratiometric sensing. The two bifunctionalized IRMOF-74 compounds exhibited pore-size-dependent sensing performance for enantiomers. This study not only provides a convenient method to construct chiral MOFs as advanced sensing materials but also reveals the fundamental of the pores in MOF-based luminescent sensors.

Enhancing water flux and antifouling properties of PES hollow fiber membranes via incorporation of surface‐functionalized Fe3O4 nanoparticles

AbstractBACKGROUNDIn this study, polyethersulfone (PES) hollow fiber membranes incorporated with surface‐functionalized iron oxide (Fe3O4) nanoparticles were developed in order to improve water flux and antifouling properties of PES membrane. Commercial Fe3O4 nanoparticles was coated by polydopamine (PDA), followed by functionalization using (3‐aminopropyl)triethoxysilane (APTES) and sulfonic acid to produce Fe3O4/PDA‐Amine and Fe3O4/PDA‐Sulf nanoparticles, respectively. All the nanoparticles‐modified membranes were synthesized using dope solution composed of different nanoparticles, followed by a series of instrumental characterization and filtration assessments.RESULTSIt is found that the membrane incorporated with Fe3O4/PDA‐Amine exhibited the best filtration performance, achieving water flux of 137.23 L m−2 h−1 bar−1 and bovine serum albumin (BSA) rejection of 92.16%. As a comparison, the pristine PES membrane only showed 82.60 L m−2 h−1 bar−1 and 71.92%, respectively. The membrane with Fe3O4/PDA‐Sulf also showed lower performance, recording 129.88 L m−2 h−1 bar−1 and 88.39%, respectively. The improved performance of the Fe3O4/PDA‐Amine‐modified PES membrane could be attributed to its lowest water contact angle (65.10°), highest porosity (68.14%), ideal pore size (65 nm) as well as good structural integrity. More importantly, the improved surface properties also led to outstanding fouling resistance, achieving flux recovery rate of 97%. This membrane also achieved excellent chemical oxygen demand (95.17%) and color (89.86%) reduction when tested using river water sample.CONCLUSIONOur work demonstrated a simple approach to functionalize the surface of Fe3O4 nanoparticles and showed the effectiveness of the surface‐functionalized Fe3O4 nanoparticles in improving not only the surface properties of PES membrane but also its filtration performance in terms of permeability, rejection and antifouling property. © 2021 Society of Chemical Industry (SCI).

Boosting formate production from CO2 electroreduction over gas diffusion electrode with accessible carbon mesopores

Electroreduction of CO2 to formate (ERCF) over a gas diffusion electrode with a Nafion-bonded carbon-supported Sn-based catalyst layer provides a promising approach for formate production. The ERCF performance is largely dependent on the carbon supports. However, the key influencing factors of the carbon supports for the ERCF performance have not yet been elucidated. We employed a variety of carbon supports with different pore structure features (activated carbon, acetylene black, and ordered mesoporous carbon) to explore the main factors influencing ERCF performance. The results showed that the pore size distribution was crucial for the ERCF performance. The ideal pore size was 5–20 nm. As it had the highest specific surface area within this pore size range among all the carbon supports examined, the ordered mesoporous carbon support obtained the highest ERCF performance (Faraday efficiency and current density for formate were 97.45 ± 2.97% and 80.12 ± 5.91 mA cm−2, respectively). Further analyses revealed that the increased ERCF performance was likely due to the large electroactive surface area, enhanced surface adsorption and activation capability of CO2, mesopore-induced proton transfer limitations for the hydrogen evolution reaction, and excellent charge transfer. This work is of significance for the further design of high-performance gas diffusion electrodes for the ERCF process.

Reproducible synthesis of all-silica CHA zeolite membranes in a homogeneous mother liquor

All-silica CHA zeolite membrane is superior to other small pore zeolite membranes because of its outstanding stability, ideal pore size and high porosity. However, the conventional synthesis of all-silica CHA membranes was constrained in a solid-like precursor which created issues like excessive consumption of raw materials and poor reproducibility. Herein, all-silica CHA membranes were prepared in a homogeneous mother liquor with (NH4)2SiF6 as silica source, which resulted into fast synthesis of thin all-silica CHA membranes with high reproducibility. Outstanding CO2-CH4 separation performance (CO2 permeance ~ 2.5 × 10-6mol/(m2 s Pa) and decent CO2-CH4 selectivity ~ 150 at room temperature and 0.14 MPa) were obtained on the 1.3 μm thick CHA membrane. This method not only simplified the conventional synthesis of all-silica CHA membranes, but also improved membrane performance with substantially reduced material cost.

Relative Importance of Stochastic Assembly Process of Membrane Biofilm Increased as Biofilm Aged.

The relative importance of different ecological processes controlling biofilm community assembly over time on membranes with different surface characteristics has never been investigated in membrane bioreactors (MBRs). In this study, five ultrafiltration hollow-fiber membranes – having identical nominal pore size (0.1μm) but different hydrophobic or hydrophilic surface characteristics – were operated simultaneously in the same MBR tank with a constant flux of 10 liters per square meter per hour (LMH). In parallel, membrane modules operated without permeate flux (0 LMH) were submerged in the same MBR tank, to investigate the passive microbial adsorption onto different hydrophobic or hydrophilic membranes. Samples from the membrane biofilm were collected after 1, 10, 20, and 30days of continuous filtration. The membrane biofilm microbiome were investigated using 16S rRNA gene amplicon sequencing from DNA and cDNA samples. Similar beta diversity trends were observed for both DNA- and cDNA-based analyses. Beta diversity analyses revealed that the nature of the membrane surface (i.e., hydrophobic vs. hydrophilic) did not seem to have an effect in shaping the bacterial community, and a similar biofilm microbiome evolved for all types of membranes. Similarly, membrane modules operated with and without permeate flux did not significantly influence alpha and beta diversity of the membrane biofilm. Nevertheless, different-aged membrane biofilm samples exhibited significant differences. Proteobacteria was the most dominant phylum in early-stage membrane biofilm after 1 and 10days of filtration. Subsequently, the relative reads abundance of the phyla Bacteroidetes and Firmicutes increased within the membrane biofilm communities after 20 and 30days of filtration, possibly due to successional steps that lead to the formation of a relatively aged biofilm. Our findings indicate distinct membrane biofilm assembly patterns with different-aged biofilm. Ecological null model analyses revealed that the assembly of early-stage biofilm community developed after 1 and 10days of filtration was mainly governed by homogenous selection. As the biofilm aged (days 20 and 30), stochastic processes (e.g., ecological drift) started to become important in shaping the assembly of biofilm community.