Silica Membranes Research Articles

Tailoring Ultramicroporosity To Maximize CO2 Transport within Pyrimidine-Bridged Organosilica Membranes.

Amine-functionalized organosilica membranes have attracted an increasing amount of attention because of significant potential for the capture of postcombustion CO2. The appealing separation performance of these membranes, however, is generally obtained via compromises to gas permeance. In the present study, a novel, ultramicroporosity-tailored composite (organo)silica membrane with high flux was synthesized via sol-gel cocondensation of a pyrimidine-bridged organoalkoxysilane precursor 4,6-bis(3-(triethoxysilyl)-1-propoxy)-1,3-pyrimidine (BTPP) with a second intrinsically rigid network precursor (1,2-bis(triethoxysilyl)ethane or tetraethylorthosilicate). The surface chemistry, ultramicroporosity, and chain-packing state of the initial BTPP-derived membranes can be carefully tuned, which has been verified via Fourier transform infrared spectroscopy, water-contact angle measurement, X-ray diffraction, and positron annihilation lifetime spectroscopy. The composite (organo)silica xerogel specimens presented a slightly improved ultramicroporosity with noticeable increases in gas adsorption (CO2 and N2). However, a surprising increase in CO2 permeance (>2000 GPU), with moderate CO2/N2 selectivity (∼20), was observed in the resultant composite (organo)silica membranes. Furthermore, gas permeance of the composite membranes far surpassed the values based on Maxwell predictions, indicating a possible molecular-scale dispersion of the composite networks. This novel, porosity-tailored, high-flux membrane holds great potential for use in industrial postcombustion CO2 capture.

Assaying for Inorganic Polyphosphate in Bacteria.

Inorganic polyphosphate (polyP) is a biological polymer found in cells from all domains of life, and is required for virulence and stress response in many bacteria. There are a variety of methods for quantifying polyP in biological materials, many of which are either labor-intensive or insensitive, limiting their usefulness. We present here a streamlined method for polyP quantification in bacteria, using a silica membrane column extraction optimized for rapid processing of multiple samples, digestion of polyP with the polyP-specific exopolyphosphatase ScPPX, and detection of the resulting free phosphate with a sensitive ascorbic acid-based colorimetric assay. This procedure is straightforward, inexpensive, and allows reliable polyP quantification in diverse bacterial species. We present representative polyP quantification from the Gram-negative bacterium (Escherichia coli), the Gram-positive lactic acid bacterium (Lactobacillus reuteri), and the mycobacterial species (Mycobacterium smegmatis). We also include a simple protocol for nickel affinity purification of mg quantities of ScPPX, which is not currently commercially available.

Toward the Formulation of Stable Micro and Nano Double Emulsions through a Silica Coating on Internal Water Droplets.

Delivery systems able to coencapsulate both hydrophilic and hydrophobic species are of great interest in both fundamental research and industrial applications. Water-in-oil-in-water (w1/O/W2) emulsions are interesting systems for this purpose, but they suffer from limited stability. In this study, we propose an innovative approach to stabilize double emulsions by the synthesis of a silica membrane at the water/oil interface of the primary emulsion (i.e., inner w1/O emulsion). This approach allows the formulation of stable double emulsions through a two-step process, enabling high encapsulation efficiencies of model hydrophilic dyes encapsulated in the internal droplets. This approach also decreases the scale of the double droplets up to the nanoscale, which is not possible without silica stabilization. Different formulation and processing parameters were explored in order to optimize the methodology. Physicochemical characterization was performed by dynamic light scattering, encapsulation efficiency measurements, release profiles, and optical and transmission electron microscopies.

Extraction of Highly Degraded DNA from Ancient Bones and Teeth.

We provide a DNA extraction protocol optimized for the recovery of highly fragmented molecules preserved within bones and teeth. In this method, the hard tissue matrix is degraded using an EDTA/Proteinase K lysis buffer, and the DNA is purified using spin columns with silica membranes. This method efficiently recovers molecules as short as 35 base-pairs long.

Progress in Modeling of Silica-Based Membranes and Membrane Reactors for Hydrogen Production and Purification

Hydrogen is seen as the new energy carrier for sustainable energy systems of the future. Meanwhile, proton exchange membrane fuel cell (PEMFC) stacks are considered the most promising alternative to the internal combustion engines for a number of transportation applications. Nevertheless, PEMFCs need high-grade hydrogen, which is difficultly stored and transported. To solve these issues, generating hydrogen using membrane reactor (MR) systems has gained great attention. In recent years, the role of silica membranes and MRs for hydrogen production and separation attracted particular interest, and a consistent literature is addressed in this field. Although most of the scientific publications focus on silica MRs from an experimental point of view, this review describes the progress done in the last two decades in terms of the theoretical approach to simulate silica MR performances in the field of hydrogen generation. Furthermore, future trends and current challenges about silica membrane and MR applications are also discussed.

Development of a Membrane Reactor using Silica Membrane and Membrane Durability

Development of a Membrane Reactor using Silica Membrane and Membrane Durability

Pervaporation properties and a semi-empirical model for removal of VOCs from water using a propyl functionalized silica membrane

Pervaporation properties and a semi-empirical model for removal of VOCs from water using a propyl functionalized silica membrane

Atmospheric–pressure Plasma–enhanced CVD of Hybrid Silica Membranes at Ambient Temperature and Pressure

Atmospheric–pressure Plasma–enhanced CVD of Hybrid Silica Membranes at Ambient Temperature and Pressure

Flame Atomic Absorption Determination of Cd and Cu in Biological Samples After Solid Phase Extraction by Octadecyl Silica Membrane Disks Modified With a Schiff Base Ligand

A procedure for separation and preconcentration of trace amounts of Cu 2+ and Cd 2+ from aqueous media is proposed. The procedure is based on the adsorption of Cu 2+ and Cd 2+ ions on octadecyl bonded silica membrane disk modified with, Pyridine 2,6-diylbis{2,2’(azamethane-1-ylidene)4-bromophenol} ( L ) at pH = 8. The ligand has been synthesized by reaction of the 2,6-diamino pyridine and 5-bromo salicylaldehyde at ethanol under refluxing. The structure of the synthesized compound resulted from the Fourier-transform infrared spectroscopy (FTIR), Proton nuclear magnetic resonance ( 1 H NMR), Mass spectrometry ( MS ) and UV spectroscopy and elemental analysis data. The solid phase extraction experimental conditions were optimized by changing several parameters such as volume of eluting solvent, the effect of pH, limit of detection and maximum capacity of the disks for Cu 2+ and Cd 2+ recovery. The retained Cu 2+ and Cd 2+ ions were then stripped from the disk with a minimal amount of 0.7 mol.L -1 nitric acid and 1 mol.L -1 hydrochloric acid solution as eluent respectively, and determined by flame atomic absorption spectrometry. The limit of detection of the proposed method was 7.6 and 3.6 ng.mL -1 for copper and cadmium ions, respectively. The method was successfully applied to determination of copper and cadmium in natural biological samples and the method was quantitative. DOI: http://dx.doi.org/10.17807/orbital.v10i7.1111

Effect of storage and DNA extraction method on 16S rRNA-profiled fecal microbiota in Japanese adults.

The effect of two factors, storage and the bacterial DNA extraction method, that potentially affect the 16S rRNA-based profiling of the microbiota in the feces of Japanese adults, were evaluated. Profiles of the microbiota in feces stored in DESS (DMSO-EDTA-salt solution) for 1, 2 and 3 weeks at room temperature, and for 3 weeks at 4°C were compared with those in fresh feces and feces stored in guanidine thiocyanate solution for 3 weeks at 4°C. None of the storage variables (preservation solution, temperature and duration) considerably affected α- and β-diversity of the fecal microbiota and OTU profiles. Regarding the bacterial DNA extraction methods, four were evaluated; A) silica membrane DNA purification combined with bead-beating bacterial disruption, B) magnetic bead DNA purification combined with bead-beating bacterial disruption, C) manual DNA purification using phenol-chloroform and ethanol precipitation combined with enzymatic bacterial lysis, and D) DNA extraction by a commercially available DNA stool kit. While methods A, B, and C did not markedly affect α- and β-diversity of the fecal microbiota and the OTU profiles, method D noticeably altered both α- and β-diversity. In addition, method D caused significant changes in the abundance of two predominant genera; Bacteroides and Bifidobacterium.

PENGELOLAAN LINGKUNGAN DENGAN CARA MEMANFAATKAN FLY ASH BATUBARA SEBAGAI BAHAN BAKU MEMBRAN SILIKA DALAM UPAYA MEMINIMALISIR LIMBAH B3 DI PT SEMEN BATURAJA OKU

The target of community service assignments in 2018 is productive communities that need development in the field of environmental management, namely employees of the Quality Control Laboratory of PT. Semen Baturaja OKU. Coal ash is a waste unlike gas from combustion, because it is a solid material that is not easily dissolved and is not volatile so it will be more troublesome in handling. If the amount is large and is not handled properly, then the coal ash can pollute the environment especially caused by fly ash and can be sucked by humans and animals can also affect the condition of the surrounding water and soil so that it can kill the plants. The chemical composition of Fly ash is silica, alumina and iron with little calcium, magnesium, sulfate, and other components. Currently coal fly ash is used in cement plants as a mixture of concrete makers. Because of the smoothness and round shape of the granules, the use of fly ash on the concrete mixture can increase the slack on the concrete mixture. The advantages of using fly ash include increasing the strength of concrete, filling the pores in the concrete so that the porosity of the concrete becomes low, while increasing the density of concrete so that it can increase the tightness of concrete to water. The coal fly ash waste that accumulates also occurs in the industry of PT Semen Baturaja Ogan Komering Ulu. PT. Semen Baturaja is one of the largest cement industries in Sumatra that produces PCC (Portland Composite Cement). PCC type cement is cement made by utilizing inorganic additives such as fly ash and trass. Aside from being an additional material for cement, fly ash can also be used as a raw material for making silica membranes which serves to reduce metal content in acid mine drainage. So that the author wishes to socialize the employees and employees of PT Semen Baturaja especially in the BTA II Quality Control laboratory division to disseminate knowledge about the benefits of coal fly ash as raw material for silica membranes in minimizing B3 waste so that environmental management with a friendly environment will achieved.

Estimation of Pore Size Distribution of Amorphous Silica-Based Membrane by the Activation Energies of Gas Permeation

Cobalt oxide silica membranes were prepared and tested to separate small molecular gases, such as He (dk = 2.6 Å) and H2 (dk = 2.89 Å), from other gases with larger kinetic diameters, such as CO2 (dk = 3.47 Å) and Ar (dk = 3.41 Å). In view of the amorphous nature of silica membranes, pore sizes are generally distributed in the ultra-microporous range. However, it is difficult to determine the pore size of silica derived membranes by conventional characterization methods, such as N2 physisorption-desorption or high-resolution electron microscopy. Therefore, this work endeavors to determine the pore size of the membranes based on transport phenomena and computer modelling. This was carried out by using the oscillator model and correlating with experimental results, such as gas permeance (i.e., normalized pressure flux), apparent activation energy for gas permeation. Based on the oscillator model, He and H2 can diffuse through constrictions narrower than their gas kinetic diameters at high temperatures, and this was possibly due to the high kinetic energy promoted by the increase in external temperature. It was interesting to observe changes in transport phenomena for the cobalt oxide doped membranes exposed to H2 at high temperatures up to 500 °C. This was attributed to the reduction of cobalt oxide, and this redox effect gave different apparent activation energy. The reduced membrane showed lower apparent activation energy and higher gas permeance than the oxidized membrane, due to the enlargement of pores. These results together with effective medium theory (EMT) suggest that the pore size distribution is changed and the peak of the distribution is slightly shifted to a larger value. Hence, this work showed for the first time that the oscillator model with EMT is a potential tool to determine the pore size of silica derived membranes from experimental gas permeation data.

Theoretical Performance Evaluation of Inorganic (Non Pd-Based) Membranes for Hydrogen Separation

The aim of this work theoretical study is to theoretically investigate a inorganic membrane assisted purifcation process of an H2-rich stream derived from a conventional methanol steam reforming stage. In particular, a black-box model for multicomponent gas mixture purifcation is developed to evaluate the H2 separation performance of such non-palladium based membranes such as silica, polymeric and carbon membranes, by varying design and processing variables such as stage cut and feed pressure. The most signifcant modeling result is achieved by using a silica membrane based separation module in which 98% of H2 purity and 0.3% of carbon monoxide in the permeate side are reached, operating with a transmembrane pressure of 4.0 bar.

High-Q inverted silica microtoroid resonators monolithically integrated into a silicon photonics platform.

We report on the monolithic integration of a new class of reflown silica microtoroid resonators with silicon nanowaveguides fabricated on top of the silica film. Connectivity with other silicon photonics devices is enabled by inversion of the toroid geometry, defined by etching a circular opening rather than a disk in an undercut silica membrane. Intrinsic quality factors of up to 2 million are achieved and several avenues of process improvement are identified that can help attain the higher quality factors (> 108) that are possible in reflown microtoroids. Moreover, due to the microtoroid being formed by standard microfabrication and post-processing by local laser induced heating, these devices are in principle compatible with monolithic co-fabrication with other electro-optic components.

From amorphous to crystalline: Transformation of silica membranes into silicalite-1 (MFI) zeolite layers

The transformation of microporous, amorphous silica membranes into b-oriented silicalite-1 (MFI) zeolite layers via in-situ crystallisation was investigated. The effect of synthesis parameters, such as the type and concentration of the silica precursor, crystallisation time and temperature, on the morphology of silicalite-1 (MFI) zeolite layers was studied. By optimizing these parameters, silicalite-1 zeolite layers were formed from the already-deposited silica layers, which promotes the crystallisation from the surface in the preferred b-orientation. The use of a monomeric silica precursor, which has slower hydrolysis kinetics than a colloidal one, resulted in the formation of zeolite crystals via heterogeneous nucleation on the surface and suppressed the formation of crystal nuclei in the liquid media via homogeneous nucleation, which then would further deposit onto the surface in a random orientation. Lastly, by optimizing the crystallisation time and temperature of the synthesis, thickness, coverage and orientation of silicalite-1 zeolite layers were controlled.

Structure-induced superhydrophilicity of silica membranes through hybridization and self-assembly of different dispersed nanoparticles

Self-assembled membranes with remarkable superhydrophilicity and high optical transparency are prepared by hybridizing dispersed silica nanoparticles of mean diameters, DS and DL (DS « DL). It has been found out in the previous work that the hybridized silica sol consisting of two dispersed nanoparticles that differ greatly in size would help lead to a smaller water contact angle for the final membrane. Among the results, one hybridized membrane containing silica nanoparticles of 45 nm and 483 nm exhibits 8.9 ± 1° as for water contact angle and 90% as for transmittance within UV–Visible region. Morphology of the membranes shows hierarchical structure or cracky layer, while the specific architecture is still influenced by the gap in particle size. As a conclusion, the process of hybridization enhances the hydrophilicity and adjusts the transmittance of membranes as well. The new method is a feasible simplification comparing with the traditional ways in attaining superhydrophilicity and we hope it will apply for other hydrophilic materials to improve their wetting ability.

Ausencia del virus de Necrosis Hematopoyética Epizoótica (EHNv) en truchas arcoíris (Oncorhynchus mykiss) enfermas en piscigranjas de la sierra del Perú

El objetivo del presente trabajo fue monitorear la detección del virus Necrosis Hematopoyética Epizoótica (EHNv) en truchas (Oncorhynchus mykiss) de piscigranjas de la Sierra del Perú. Se tomaron muestras de 111 peces enfermos (hígado, bazo, riñón anterior) de piscigranjas de las regiones de Áncash, Junín y Huancavelica, Perú. Las muestras de tejidos fueron procesados de inmediato para el aislamiento bacteriano y otro grupo de muestras fueron conservadas a -196 °C para el PCR. El ADN de cada tejido fue extraído mediante el método del Trizol y luego purificado con membranas de sílica (PureLinkGenomic DNA kit). El PCR se realizó utilizando los cebadores MCP-1 específicos para el EHNv siguiendo la metodología propuesta por la OIE y con el kit comercial VetPCRTM EHNV Detection para su confirmación. El aislamiento bacteriano se realizó con el sembrado en agar TSA y Anacker-Ordal (agar citófaga) de cada tejido y la identificación mediante tinción Gram y bioquímica bacteriana. No se detectó el ADN del EHNv en las muestras indicando que la prevalencia del virus es menor al 5% o no está presente en las piscigranjas muestreadas. Se aisló Yersinia ruckeri y Aeromonas spp en todas las muestras, indicando que la causa de la enfermedad y mortalidad presente en las piscigranjas se debían a la infección con estas bacterias.

Sol–gel-derived multifunctional nanoporous ceramic membranes

The sol–gel process offers a wide range of opportunities in terms of tailored nanostructures and nanoporous layers. Here, this is illustrated with various examples of sol–gel-derived multifunctional nanoporous membranes. Hierarchically porous silica membranes and the implementation of different strategies for their functionalization as catalytic membranes are first described. The second part deals with sol–gel-derived photocatalytic membranes and with sol–gel-derived nanoporous membranes enabling reversible chemisorption of hydrogen sulfide.

Fabrication of Silica Membrane through Surface‐Induced Condensation on Porous Block Copolymer

AbstractNanoporous structures generated from micro‐phase separation of block copolymers (BCPs) have been used as templates for fabrication of inorganic materials through atomic layer deposition (ALD), chemical vapor deposition, sol‐gel process, and electrodeposition. However, the previous deposition methods are suffering from unmanageable preparation conditions and demanding technical requirements. In this work, bioinspired synthesis was used as replicating technique to fabricate silica porous membrane on swelling‐induced polystyrene‐block‐poly (2‐vinyl pyridine) (PS‐b‐P2VP) membrane with bicontinuous nanopores. It was found that silica nanoporous membranes were successfully obtained on PS‐b‐P2VP under benign conditions (near‐neutral pH, low temperature, and ambient pressure) from tetraethoxysilane (TEOS). Moreover, the thickness of silica films could be regulated by the amount of water in the TEOS solution. The mechanism could be inferred that pyridine groups in P2VP domains can act as a catalyst for the insertion and polymerization reactions of silanol from hydrolysis of TEOS to form silica due to the hydrogen bonding between pyridine groups and Si‐OH in silanol. The proposed method offers a facile and controllable synthesis strategy to fabricate nanoporous silica membrane.

Modeling and Optimization on the Carbon Dioxide Separation from Natural Gas Using Hydrotalcite-Silica Membrane

The process modeling and optimization of carbon dioxide (CO2) separation from carbon dioxide-methane (CH4) binary gas mixture through hydrotalcite (HT)-silica membrane using statistical design of experiments (DoE) is reported in this study. The effect of three important process variables, pressure difference across the membrane (100-500 kPa), temperature (30-190oC) and CO2 feed concentration (10-50%) on the CO2 separation performance of the membrane were investigated. The response surface methodology (RSM) coupled with central composite design (CCD) was used to build up two models to correlate the effect of process conditions to CO2 permeance and CO2/CH4 separation selectivity. The analysis of variance (ANOVA) of the quadratic model at 95% confidence interval confirmed that the model was highly significant. The CO2 feed concentration with 43% showed the best performance with a CO2 permeance of 6.0x10-7 mol.m-2.s-1.Pa-1 and a CO2/CH4 separation selectivity of 109 at 100 kPa pressure difference across the membrane and temperature of 30oC