Narrow Pore Size Distribution Research Articles

Efficient preparation of P-doped carbon with ultra-high mesoporous ratio from furfural residue for dye removal

P-doped mesoporous carbon material is receiving increasing attention in various fields due to its special physicochemical properties, but the research in the field of pollutant removal is rarely reported. Herein, P-doped furfural residue-based carbon materials (PFRC) with ultra-high mesoporous ratio (93.9%), narrow pore size distribution and large surface area (1769.4 m2 g−1) was prepared by a simple method of fast pyrolysis of phosphoric acid treated furfural residue (FR). A series of characterizations were carried out to explore the physicochemical properties and P-doping mechanism of the materials systematically. With the increase of the activation temperature, the evolution of the P-doped structure is as follows: adsorbed phosphate → P-O-Caromatic → O3P-Caromatic → O2P-C2aromatic → OP-C3aromatic. The PFRC500 prepared at 500 °C has the most abundant P-O-Caromatic and P-Caromatic structures, which lead to a higher specific surface area, more developed pore structure and more graphite edge defects than other PFRCs. Methylene blue (MB) adsorption studies showed that PFRC500 had a good adsorption performance with 486 mg g−1 equilibrium adsorption capacity and 97.2% of removal rate (T = 298 K, C0 = 100 mg L−1). The adsorption kinetics and thermodynamics were studied. The role of P structure in MB adsorption was explored for the first time. the adsorption mechanism was explored. The P-O-Caromatic, O3P-Caromatic and O2P-C2aromatic structures are the main chemical adsorption sites, but C3aromatic-PO is not. This work can provide guidance for the design of P-doped mesoporous carbon materials with better adsorption performance in the future.

Mesoporous alumina-supported layered double hydroxides for efficient CO2 capture

A novel kind of CO2 solid adsorbents (xLDH/MA, x is the loading of LDH) was prepared by loading of layered double hydroxides (LDH) on the mesoporous alumina (MA) support. The LDHs in xLDH/MA were evenly distributed on the surface of MA. xLDH/MA possessed a large BET surface area (278–378 m2/g), narrow pore-size distribution (4.37–6.23 nm), and a highly crystalline framework. Among all of the samples, 30LDH/MA showed an excellent CO2 adsorption capacity at 50 °C (1.56 mmol/g), which was 1.55 times larger than that of unmodified MA. Due to the synergistic effect between MA and LDH, 30LDH/MA exhibited a higher surface area and a more amount of adsorption sites, which were the main factors improving its CO2 adsorption performance. The adsorption process of CO2 on xLDH/MA was dominated by the chemical adsorption, and the adsorbed CO2 was mainly stored in the form of carbonate. In addition, the 30LDH/MA composite material showed fast adsorption kinetics and good regeneration efficiency. We believe that such a kind of porous alumina-supported layered double hydroxides would have a great potential in the applications for the adsorption of CO2.

Efficient conversion of glucose into 5-HMF catalyzed by lignin-derived mesoporous carbon solid acid in a biphasic system

A lignin-derived mesoporous carbon solid acid (LDMCS) catalyst was prepared by high temperature carbonization and subsequent sulfonation treatment using alkali lignin as the carbon source and KCl as a salt template. The prepared LDMCS has an irregular mesoporous structure with a narrow pore size distribution (concentrated at 4 nm), large specific surface area (1123.0 m2 g−1) and high -SO3H group density (2.20 mmol g−1). Compared with other types of solid acids reported in the literature, the prepared LDMCS catalyst has equivalent or better catalytic performance in the catalytic conversion of glucose to 5-hydroxymethylfurfural (5-HMF). A glucose conversion of 97.7% and a 5-HMF yield of 57.8% were obtained with the aqNaCl-THF (1:3) biphasic solvent system under the optimized reaction conditions with reaction temperature of 160 °C, reaction time of 2.5 h, and catalyst loading of 1 mg mg−1. More importantly, the 5-HMF yield still reached 40.9% after 5 cycles of the catalyst use, indicating that there was no significant loss of catalytic activity.

Hierarchical Catalysts Prepared by Interzeolite Transformation.

Interzeolite transformation has been used to produce a novel family of hierarchical catalysts featuring excellent textural properties, strong acidity, and superior catalytic performance for the Friedel–Crafts alkylation of indole with benzhydrol, the Claisen–Schmidt condensation of benzaldehyde and hydroxyacetophenone, and the cracking of polystyrene. Intermediate solids of the FAU interzeolite transformation into BEA display both increased accessibility—due to the development of mesoporosity—and strong acidity—caused by the presence of ultrasmall crystals or zeolitic fragments in their structure. The use of surfactants allows for the development of the hierarchical catalysts with very narrow pore size distribution. The properties of interzeolite transformation intermediates (ITIs) can be fine-tuned simply by stopping the interconversion at different times.

Polyarylester thin films with narrowed pore size distribution via metal-phenolic network modulated interfacial polymerization for precise separation

Traditional nanofiltration (NF) membranes meet a bottleneck in throughput due to the lack of flexibility in pore structure control of the polyamide selective layer. This work developed a highly-permselective NF membrane by creating a controlled polyarylester selective layer via a facile method of metal-phenolic network (MPN) modulated interfacial polymerization between 5,5,6′,6′-tetrahydroxy-3,3,3′,3′-tetramethyl spirobisindane (TTSBI) and trimesoyl chloride (TMC). It was hypothesized that in the presence of FeCl3, the catechol groups of TTSBI first formed a Fe3+/TTSBI complex to construct the MPN and subsequently reacted with TMC, eliminating structural defects in the selective layer. The solution chemistry studies and membrane optimization results verified the significant role of Fe3+ in forming metal-phenolic coordination and thus defectless pore structure. The resulted Fe-TTSBI-TMC membrane exhibited greatly reduced pore size of 0.68 nm and narrow pore size distribution. The rigid and twisted feature of TTSBI endowed the polyarylester layer with high porosity. This ingeniously designed synergistic effect rendered the resulted membrane with a high pure water permeability of 15 L m−2 h−1 bar−1, about 3 times higher than typical polyamide NF membrane prepared by piperazine and TMC; while achieved high salt and molecular rejections (e.g., 98% rejection of Na2SO4, 100% rejection of vitamin B12), exhibiting superior perm-selective properties as compared to most NF membranes incorporating microporous materials. Accurate separation between molecules of different sizes of vitamin B2 and vitamin B12 was achieved with 100% efficiency. Hence, this work provides a promising alternative for skillful control of NF membrane pore structure towards efficient and precise molecular separation.

Supercritical Foaming and Impregnation of Polycaprolactone and Polycaprolactone-Hydroxyapatite Composites with Carvacrol

Polycaprolactone (PCL) and polycaprolactone-hydroxyapatite (PCL-HA) scaffolds were produced by foaming in supercritical carbon dioxide (scCO2) at 20 MPa, as well as in one-step foaming and impregnation process using carvacrol as an antibacterial agent with proven activity against Gram-positive and Gram-negative bacteria. The experimental design was developed to study the influence of temperature (40 °C and 50 °C), HA content (10 and 20 wt.%), and depressurization rate (one and two-step decompression) on the foams’ morphology, porosity, pore size distribution, and carvacrol impregnation yield. The characterization of the foams was carried out using scanning electron microscopy (SEM, SEM-FIB), Gay-Lussac density bottle measurements, and Fourier–transform infrared (FTIR) analyses. The obtained results demonstrate that processing PCL and PCL-HA scaffolds by means of scCO2 foaming enables preparing foams with porosity in the range of 65.55–74.39% and 61.98–67.13%, at 40 °C and 50 °C, respectively. The presence of carvacrol led to a lower porosity. At 40 °C and one-step decompression at a slow rate, the porosity of impregnated scaffolds was higher than at 50 °C and two- step fast decompression. However, a narrower pore size distribution was obtained at the last processing conditions. PCL scaffolds with HA resulted in higher carvacrol impregnation yields than neat PCL foams. The highest carvacrol loading (10.57%) was observed in the scaffold with 10 wt.% HA obtained at 50 °C.

Poly(vinylidene fluoride) (PVDF) membrane fabrication with an ionic liquid via non-solvent thermally induced phase separation (N-TIPs)

In this paper, ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate was the first time successfully utilized as single solvent in preparing the PVDF membrane with a good performance by N-TIPs method. The effects of quenching temperature and hydrophilic additive content on the morphology, permeability, and strength of the membranes were studied. All the prepared PVDF membranes were proved to be a pure β phase by FTIR and XRD, possessing a narrow pore size distribution. By adjusting quenching temperature and additive content, membranes with a flux of 383.2 L/m2 h and concentrated pore diameter of 26 nm obtained.

Effect of pore structure on Ni/Al2O3 microsphere catalysts for enhanced CO2 methanation

An understanding of the support effect is fundamental for guiding the rational design of heterogeneous catalysts. Herein, the role of pore structure on metal dispersion and catalytic performance was comprehensively investigated using Ni/Al2O3 catalysts. Three different Al2O3 supports, including Al2O3 microspheres prepared in microchannels and two commercially available Al2O3 supports named Sample 1 and Sample 2, were used and the Ni/Al2O3 catalysts were prepared by wetness impregnation method. X-ray diffraction, transmission electron microscopy, H2 temperature-programmed reduction, X-ray photoelectron spectroscopy, N2 adsorption–desorption, and H2 pulse chemisorption analyses combined with a sintering kinetic model were used to investigate the effect of the support pore structure. The narrow pore size distribution (3–15 nm) of Al2O3 microspheres and Sample 1 led to a uniform NiO dispersion for the calcined catalysts. Moreover, the high specific surface area (291 m2/g) and large pore volume (1.0 mL/g) of the Al2O3 microspheres were beneficial for the deposition of NiO particles inside mesopore to obtain a stronger metal–support interaction. Owing to the smaller NiO nanoparticles and stronger metal–support interaction, the reduced Ni/Al2O3 microspheres exhibited an average Ni particle size of 10.2 nm under 36 wt% nickel loading, whereas the average Ni particle size loaded on Sample 1 and Sample 2 were 12.6 nm and 13.2 nm, respectively. The optimized CO2 conversion of 87.0% at 300 °C under atmospheric pressure was attributed to the large pore volume and uniform Ni dispersion of Ni/Al2O3 microsphere catalysts while the same value for Sample 1 and Sample 2 catalysts was 81.5% and 55.0%, respectively. This work provides valuable guidelines for designing effective CO2 methanation support and proves the potential application of Al2O3 microspheres for CO2 methanation.

Mesoporous Bioglasses Enriched with Bioactive Agents for Bone Repair, with a Special Highlight of María Vallet-Regí's Contribution.

Throughout her impressive scientific career, Prof. María Vallet-Regí opened various research lines aimed at designing new bioceramics, including mesoporous bioactive glasses for bone tissue engineering applications. These bioactive glasses can be considered a spin-off of silica mesoporous materials because they are designed with a similar technical approach. Mesoporous glasses in addition to SiO2 contain significant amounts of other oxides, particularly CaO and P2O5 and therefore, they exhibit quite different properties and clinical applications than mesoporous silica compounds. Both materials exhibit ordered mesoporous structures with a very narrow pore size distribution that are achieved by using surfactants during their synthesis. The characteristics of mesoporous glasses made them suitable to be enriched with various osteogenic agents, namely inorganic ions and biopeptides as well as mesenchymal cells. In the present review, we summarize the evolution of mesoporous bioactive glasses research for bone repair, with a special highlight on the impact of Prof. María Vallet-Regí´s contribution to the field.

Mesoporous alumina: A comprehensive review on synthesis strategies, structure, and applications as support for enhanced H2 generation via CO2-CH4 reforming

Lately, the generation of hydrogen out from carbon dioxide (CO2) - methane (CH4) reforming has been touted as a feasible option for reducing two of the most harmful greenhouse gases (CO2 and CH4) in the atmosphere. However, this technology typically suffered from catalyst deactivation triggered by sintering and coke deposition. Therefore, designing a feasible catalyst by making efficient support selections is vital for overcoming this challenge. Mesoporous alumina (MA) has aroused great attraction attributed to their potential applications as catalysis supports resulted from their high surface areas combined with tunable, narrow, and uniform pore size distribution, as well as their ability to constrain active metal from sintered and deactivated during the reaction. These materials' morphology, composition, and pore structure can be directly tailored during synthesis by altering the synthesis parameters like the type of the surfactants/templates employed, pH conditions, or selection of alumina precursors. As a result, this review's major focus is on synthesizing unique MA using a range of synthesis routes and conditions. Apart from that, this review also focuses on the applications and performance of MA as catalyst support during the CO2-CH4 reforming. We believe that this effort provides the complete grasp of MA contribution towards improving the CO2-CH4 reforming activity.

Structure and Pore Size Distribution in Nanoporous Carbon

We study the structural and mechanical properties of nanoporous (NP) carbon materials by extensive atomistic machine-learning (ML) driven molecular dynamics (MD) simulations. To this end, we retrain a ML Gaussian approximation potential (GAP) for carbon by recalculating the a-C structural database of Deringer and Csányi adding van der Waals interactions. Our GAP enables a notable speedup and improves the accuracy of energy and force predictions. We use the GAP to thoroughly study the atomistic structure and pore-size distribution in computational NP carbon samples. These samples are generated by a melt-graphitization-quench MD procedure over a wide range of densities (from 0.5 to 1.7 g/cm3) with structures containing 131 072 atoms. Our results are in good agreement with experimental data for the available observables and provide a comprehensive account of structural (radial and angular distribution functions, motif and ring counts, X-ray diffraction patterns, pore characterization) and mechanical (elastic moduli and their evolution with density) properties. Our results show relatively narrow pore-size distributions, where the peak position and width of the distributions are dictated by the mass density of the materials. Our data allow further work on computational characterization of NP carbon materials, in particular for energy-storage applications, as well as suggest future experimental characterization of NP carbon-based materials.

Preparation of high pore volume γ-Al2O3 nanorods via “gibbsite-AACH” precursor route in a membrane dispersion microreactor

In this work, several mesoporous γ-Al2O3 nanorods with high pore volume and narrow pore size distribution were controllable prepared via “gibbsite-AACH (ammonium aluminum carbonate hydroxide)” precursor route in a membrane dispersion microreactor. The effects of reaction temperature, (NH4)2CO3 concentration and calcination temperature on the samples were intensively studied. The highly uniformed morphology was assured due to the high mixing intensify in the membrane dispersion microreactor and the successful conversion of the precursor in the slurry. Under optimal conditions, these as-prepared γ-Al2O3 nanorods behaved high pore volume of 1.65 mL/g and narrow pore size distribution of 3–20 nm with a length and width of 150–200 nm and 30–60 nm, respectively. Furthermore, the adsorption experiment of the prepared samples were carried out under natural pH value, and the as-prepared sample of AACH-500 exhibited favorable adsorption performance for Congo red (CR) solution. The maximal adsorption capacity was up to 2006.7 mg/g, thus indicating that the as-prepared mesoporous γ-Al2O3 nanorods are in adsorption and other application potential of the field.

Improvement of barium tungsten cathode and investigation of thermionic emission performance

<sec>The Ba-W cathode consists of the porous W matrix and the aluminate. During cathode operation, the Ba atoms are generated in the pores through the thermal reaction between the W and aluminate, and then diffuse along the pore channels to the W surface, lowering the work function. Therefore, the Ba yield and the Ba diffusion are significantly influenced by the micro pore structure of the matrix and the phase composition of the aluminate.</sec><sec>Firstly, the matrix is fabricated with the narrow particle size distribution powder by the spark plasma sintering (SPS) technique, which shows the narrow pore size distribution (FWHM = 0.43 μm). Then the spherical powder with good fluidity and high tap density is prepared using the RF induction thermal plasma. The matrix prepared with spherical powder exhibits narrower pore size distribution (FWHM = 0.4 μm), smooth pore channels and good inter-pore connectivity. The two matrixes prepared with narrow particle powder and spherical powder are named N-matrix and S-matrix, respectively.</sec><sec>The aluminates are prepared using the solid phase method and the liquid phase method, separately. The particles of solid phase aluminate precursor present all shapes and all sizes, while the particles of the liquid phase aluminate precursor are uniform in size and identical in shape. The phase of solid phase aluminate and the phase of liquid phase aluminate are analyzed by XRD, the results show that the former consists of the effective Ba<sub>3</sub>CaAl<sub>2</sub>O<sub>7</sub> phase and other impurity phases, while the latter is composed of two effective phases of Ba<sub>3</sub>CaAl<sub>2</sub>O<sub>7</sub> and Ba<sub>5</sub>CaAl<sub>4</sub>O<sub>12</sub>.</sec><sec>The N+S and S+S cathodes are obtained by using the solid phase aluminate to impregnate the N-matrix and the S-matrix, and the <i>U</i>-<i>j</i> characteristics of the two cathodes are investigated. The double logarithmic curves of <i>U</i> and <i>j</i> show that the slope of 1.37 in the space charges limited (SCL) region for the S + S cathode is higher than that of 1.25 for the N+S cathode, so the S+S cathode exhibits better emission uniformity. The current density at the deviation point (<i>j</i><sub>DEV</sub>) of the N+S cathode and that of the S+S cathode are 6.6 A·cm<sup>–2</sup> and 6.96 A·cm<sup>–2</sup>, respectively. So the improvement on the matrix obviously raises the emission uniformity of cathode, but the current density is increased less.</sec><sec>Based on the excellent matrix of the S+S cathode, the S+L cathode is obtained by improving the aluminate of the S+S cathode with liquid phase aluminate. The <i>U</i>-<i>j</i> characteristics show the slope of the S+L cathode reaches to 1.44, and the <i>j</i><sub>DEV</sub> is 21.2 A·cm<sup>–2</sup>. So the improvement on the aluminate not only increases the uniformity, but also raises the current density.</sec><sec>The present study shows that the <i>U-j</i> curve calculated from the classical thermionic emission (TE) theory accords well with that of the S + L cathode at 1000 ℃, which indicates that the Ba-W cathode follows the classical TE theory rather than other emission theories, and the Ba-O dipole layer just changes the work function of the cathode.</sec>

Effect of surface area on electrical properties of NiCo2O4-reduced graphene oxide nanocomposites for supercapacitor electrodes applications

Based on the method of electrical charge storage, supercapacitors are divided into two categories, double-layer electrical capacitor (EDLC) and pseudocapacitors. Utilizing three processes—reversible adsorption, redox reactions on metal oxides, and reversible electrochemical—pseudocapacitors are utilized for high power applications involving metal oxide electrodes and the transfer of electric charge based on a reversible faradaic. In the fabrication of supercapacitors, a high specific surface area with a relatively narrow pore size distribution is essential. Therefore, it is required to increase the capacitance of the material. In this work, nickel cobaltite (NiCo2O4) synthesized from nanocomposite NiS·5H2O and Co2SO4·7H2O precursors were mixed with reduced graphene oxide (rGO). Coprecipitation and calcination were used to create the nanocomposites. The produced NiCo2O4/rGO nanocomposite was used as a pseudocapacitive supercapacitor electrode. The results showed that sample code S2 with mass variations of NiO, Co3O4, and rGO at a ratio of 2:3:2 had the best performance. The sample had a hexahedron-shaped surface morphology, an average particle size of about 0.005 m2, a specific surface area of 12.75 m2/g, an average pore radius of 9.534 nΩ.m, and a pore volume of 0.06404 cm3/g. It also performed exceptionally well in terms of electrical conductivity of 6.078 S/m,electrical resistivity of 0.16 nΩ.m, and capacitance of 289.93 F/g.

Study on the removal of the static Cr (VI) in water by graphene hydrogel (rGH)

In this study, the reduced graphene hydrogel rGH with three-dimensional structure was prepared by chemical reduction method, that the adsorption and removal performance of heavy metal Cr (VI) in water was discussed. Graphene hydrogel is capable of high specific surface area, three-dimensional structure and narrow pore size distribution. Moreover, there are a large number of oxygen-containing functional groups such as hydroxyl groups on the surface of the material. Graphene hydrogel can remove Cr (VI) in water efficiently and continuously, and the removal of Cr (VI) in 1 ppm can keep over 99.5% in 6 hours, indicating the excellent application.

MESOPOROUS Na2Ti3O7 NANOTUBE-CONSTRUCTED MATERIALS WITH HIERARCHICAL ARCHITECTURE: SYNTHESIS AND PROPERTIES

Recently, design of hierarchical materials with remarkable and unusual properties, useful for practical applications, has become more and more meaningful in nanosciences and nanoengineering. This report presents a method of fabricating Na2Ti3O7-based materials with hierarchical two-level (micro/nano) architecture. The products are microparticles constructed of thin-walled nanotubes having an outer diameter of 6–9 nm, wall thickness of 2–3 nm, and length of several hundred nanometers. The synthesis was carried in hydrothermal conditions at 130 °C for 36 h in a highly alkaline medium (10M NaOH aqueous solution). The obtained hierarchical materials exhibit surface roughness and porosity (specific surface area of 314 m2/g and pore volume of 0.54 cm3/g are achieved) with a narrow pore-size distribution in the mesopore range (average pore diameter is around 5.7 nm). Phase formation of products has been studied as a function of calcination temperature. It was found that Na2Ti3O7-based materials is obtained for calcination conditions of near 350 °C. Higher temperatures (more than 500 °C) favored anatase TiO2 formation. There are no significant changes were detected in morphology and texture of products calcined at 350 °C. An electrical conductivity of over 10–3 S/cm at room temperature was registered for materials. Besides, it is increased for three times after thermal treatment at 350 °C. The results suggest that obtained hierarchical nanotube-constructed porous Na2Ti3O7 microparticles can be involved for various industrial uses, including next generation electrochemical power sources.

Pore size control of monodisperse mesoporous silica particles with alkyl imidazole ionic liquid templates for high performance liquid chromatography applications

The control of pore size in mesoporous silica particles is still a topic of considerable research attention for the preparation of chromatographic packing materials. In this study, three alkyl imidazole ionic liquid surfactants ([BRIJOn-MIM]Ts (n = 2, 10, 20)) were synthesized from polyoxyethylene oleyl ether (BRIJ™On, n = 2, 10, 20), 1-methylimidazole, and p-toluenesulfonyl chloride. [BRIJOn-MIM]Ts (n = 2, 10, 20) exhibited different template behaviors in the preparation of mesoporous silica, and hollow silica with worm-like vesicle structures, spherical silica, and gel were obtained, respectively. Monodisperse sub-3 µm core-shell silica particles (CSSPs) with narrow pore size distribution were successfully prepared by the ultrasound-assisted sol-gel method using [BRIJO10-MIM]Ts as the template. A shell thickness of up to 300 nm was obtained, and the pore size was expanded from 4.7 to 7.3 nm by adjusting the reaction parameters, overcoming the limitation of pore size to less than 4 nm when using organic alkyl quaternary ammonium or alkyl imidazolium surfactants as the templates. The synthesized 2.7 µm CSSPs were functionalized with tert-butylcarbamoylated quinine and used as an anion exchange chiral stationary phase, exhibiting excellent separation performance for N-substituted amino acid enantiomers.

A study on the mechanism of pore formation through VIPS-NIPS technique for membrane fabrication

In this research, the pore formation mechanism of the membranes through the vapor-induced phase separation (VIPS) technique is studied. Polyvinylidene Fluoride (PVDF) microfiltration membranes are successfully fabricated by a combination of the vapor-induce phase separation (VIPS) and non-solvent-induced phase separation (NIPS), known as VIPS-NIPS method, and the influence of exposure time is investigated on the characteristics of the fabricated membranes. The membranes are characterized by scanning electron microscope (SEM) images, porosity, maximum pore radius, pore size distribution (PSD), liquid entry pressure of water (LEPw), mechanical strength, and flux of ethanol through the membrane. The results demonstrated the pore radius of the membranes increased, then decreased, and then increased again by increasing the exposure time. The narrowest pore size distribution was obtained for the membranes when the polymeric film was exposed to the humid environment for five minutes. The pore size distribution results confirmed the four-step mechanism for pore formation in the VIPS process. The nucleation points are formed on the membrane surface in the VIPS step. At low exposure times, the number of nuclei is low and they grow in the coagulation bath and form large pores. By increasing the exposure time, the number of nuclei is increased and reaches a maximum value. At this point, the growth of nuclei in the coagulation bath is minimum and results in a membrane with a smaller pore radius. Afterward, by increasing the VIPS time, the nuclei become larger and join each other to make larger pores, therefore, a wider pore size distribution with a larger average pore radius of the membrane would be expected.

Effect of parameters on ME process by near-field electrospun PTFE membrane

BackgroundMembrane emulsification (ME) is an attractive membrane process to produce various kind of simple or multiple emulsions. The membrane utilized in ME process should have high dispersed phase flux, narrow pore size distribution and excellent antifouling property. MethodsThis work proposed a novel near-field electrospun (NFES) poly(tetrafluoroethylene) (PTFE) membranes with ordered rectangular pore geometry. Compared with other membranes, the order pore geometry of NFES PTFE membrane was helpful to obtain a more homogeneous and more stable water-in-oil (W/O) emulsion. Significant findingsThe droplet size was simply controlled by the NFES PTFE membrane pore size. And NFES PTFE membrane was more conducive to the formation of droplets with narrow droplet size distribution because of its unique straight rectangular membrane pore geometry. In addition, W/O emulsion droplet size be regulated in coordination with operating parameters and phase parameters. Results indicated that a smaller rectangular pore area of PTFE membrane would lead to a smaller droplet size. Introducing of shear stress in the continuous phase was contributed to the generation of monodisperse droplets. When the emulsifier (Span 80) content was 1wt%, the smallest droplet size (∼103.6 nm) was obtained.

Dynamic streaming potential coupling coefficient in porous media with different pore size distributions

SUMMARY Seismoelectric signals are generated by electrokinetic coupling from seismic wave propagation in fluid-filled porous media. This process is directly related to the existence of an electrical double layer at the interface between the pore fluid and minerals composing the pore walls. The seismoelectric method attracts the interest of researchers in different areas, from oil and gas reservoir characterization to hydrogeophysics, due to the sensitivity of the seismoelectric signals to medium and fluid properties. In this work, we propose a physically based model for the dynamic streaming potential coupling coefficient (SPCC) by conceptualizing a porous medium as a bundle of tortuous capillaries characterized by presenting different pore size distributions (PSD). The results show that the dynamic streaming potential coupling coefficient is a complex function depending on the properties of pore fluid, mineral–pore fluid interfaces, microstructural parameters of porous media and frequency. Parameters influencing the dynamic SPCC are investigated and explained. In particular, we show that the PSD affects the transition frequency as well as the shape of the SPCC response as a function of frequency. The proposed model is then compared with published data and previous models. It is found that the approach using the lognormal distribution is in very good agreement with experimental data as well as with previous models. Conversely, the approach that uses the fractal distribution provides a good match with published data for sandstone samples but not for sand samples. This result implies that the fractal PSD may not be pertinent for the considered sand samples, which exhibit a relatively narrow distribution of pore sizes. Our proposed approach can work for any PSD, for example, including complex ones such as double porosity or inferred from direct measurements. This makes the proposed models more versatile than models available in literature.