Pore Size Distribution Measurements Research Articles

Closure to “A new suction method for the measurement of pore size distribution of filter layer in permeable formwork” by Zhenghong Tian, Xiaodong Wang and Xudong Chen

It is of great help to take a new looking at our findings. For the questions put forward by Dr. Rawal, our response is presented in this paper. The description of permeable formwork in the original paper was simplified due to space limitations. The external pressure has little impact on the pore structure of the permeable formwork.

Vapour phase dehydration of glycerol to acrolein over tungstated zirconia catalysts

Abstract Tetragonal (TZ) and monoclinic (MZ) polymorphs of zirconia supports were synthesised by sol–gel method followed by variation of the calcination temperature. Tungstated (10 wt% WO 3 ) supported on the zirconia polymorphs were prepared by impregnation method by using ammonium metatungstate precursor. The physico-chemical properties of the calcined catalysts were characterised by X-ray diffraction, UV–vis diffused reflectance spectroscopy, X-ray photoelectron spectroscopy (XPS), surface area and pore size distribution measurements to gain insight into the effect of morphology of the catalyst textural properties, and structure. The surface acidic properties have been determined by NH 3 TPD method and also with FT-IR spectra of pyridine adsorption. Vapour phase dehydration of glycerol to acrolein was employed to investigate the catalytic functionalities. Glycerol conversion and acrolein selectivity was mainly dependent on the fraction of moderate acid sites with majority of them are due to Bronsted acidic sites. Monoclinic zirconia based catalysts have shown the highest activity and acrolein selectivity compared to the corresponding tetragonal zirconia catalysts.

Oxidation of Rhodamine B in aqueous medium in ambient conditions with raw and acid-activated MnO2, NiO, ZnO as catalysts

Various catalysts have been utilized for wet oxidation of organic compounds in water. Rhodamine B is a cationic xanthene dye, used in a large number of industries and is considered as an undesirable chemical in water. In the present work, commercially available metal oxides, MnO2, NiO and ZnO, and those activated by treating with 1.0N H2SO4 were used to oxidize the dye in water to innocuous compounds. The catalysts were characterized with FTIR, XRD, SEM, cation exchange capacity and BET surface area, pore volume and pore size distribution measurements. Oxidation was carried out in a batch reactor at ambient temperature and pressure under different conditions of pH, reaction time, dye concentration, catalyst loading, and temperature. Acid-activated MnO2 was the best catalyst with almost 100% Rhodamine B oxidation (dye 1.0mg/L, catalyst loading 2.5g/L). The catalysts could be recovered and reused. Oxidation followed first order kinetics and a reaction mechanism was proposed based on analysis of the products.

Water Adsorption in Nanoporous Carbon Characterized by in Situ NMR: Measurements of Pore Size and Pore Size Distribution

We report an in situ nuclear magnetic resonance (NMR) study of water adsorption in a series of activated carbon samples with pore sizes of a few nanometers down to the subnanometer scale (nanoporous carbon). Water adsorption exhibits S-shaped type V isotherms with a steep increase near a certain vapor pressure. Using a previously proposed water isotherm model, pore size and pore size distribution are derived from the in situ NMR data, and they are shown to be in good agreement with results derived from N2 adsorption. The change of 1H NMR spin–lattice relaxation time of adsorbed H2O with vapor pressure is consistent with the mechanism of water cluster formation at surface groups preceding the occurrence of pore filling. NMR spectra of high pressure H2 gas in nanoporous carbon with preadsorbed D2O proves unambiguously that water preferentially fills the smaller nanopores. These results suggest that water adsorption can potentially be used for the characterization of pore structures of nanoporous carbon, and that in situ NMR is a convenient method for water isotherm measurement with accompanying microscopic information.

Vapour phase hydrogenolysis of glycerol over nano Ru/SBA-15 catalysts on the effect of preparatory routes and metal precursors.

The effect of preparation method and metal precursor of ruthenium employed during the preparation of Ru/SBA-15 catalysts were investigated. The catalytic functionalities are evaluated during the vapour phase hydrogenolysis of glycerol to 1,2-propyleneglycol, 1,3-propylene glycol and ethylene glycol. The catalysts exhibit high conversion/selectivity for 3 wt%Ru (3Ru/SBA-15) catalysts during glycerol hydrogenolysis. CO-chemisorption results suggest that the variation in the dispersion of Ru on SBA-15 support. These catalysts were characterized by XRD, TPR, TEM, BET surface area, pore size distribution and CO-chemisorption measurements. The Ru/SBA-15 catalysts synthesized from micro-emulsion method and polyol method have shown higher catalytic activity than the samples prepared by impregnation method and deposition-precipitation method. The catalytic behavior during glycerol hydrogenolysis is attributed to the formation of nano particles of ruthenium.

A new suction method for the measurement of pore size distribution of filter layer in permeable formwork

A water suction method for determining pore size distributions have been developed that is especially used for, but not restricted to, characterizing filter layer in permeable formwork. The laboratory method was presented for determining the distributions of pore sizes. The construction and the use of the apparatus are outlined. Results from three kinds of permeable formwork are analyzed and interpreted. The test results are compared with that obtained by the existing theories to predict the pore size distribution of nonwoven structures. The comparisons between measured and predicted pore size distributions confirmed the good accuracy of the Faure model.

WO3 Nanolamella Gas Sensor: Porosity Control Using SnO2 Nanoparticles for Enhanced NO2 Sensing

Tungsten trioxide (WO3) is one of the important multifunctional materials used for photocatalytic, photoelectrochemical, battery, and gas sensor applications. Nanostructured WO3 holds great potential for enhancing the performance of these applications. Here, we report highly sensitive NO2 sensors using WO3 nanolamellae and their sensitivity improvement by morphology control using SnO2 nanoparticles. WO3 nanolamellae were synthesized by an acidification method starting from Na2WO4 and H2SO4 and subsequent calcination at 300 °C. The lamellae were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), which clearly showed the formation of single-crystalline nanolamellae with a c-axis orientation. The stacking of each nanolamella to form larger lamellae that were 50-250 nm in lateral size and 15-25 nm in thickness was also revealed. From pore size distribution measurements, we found that introducing monodisperse SnO2 nanoparticles (ca. 4 nm) into WO3 lamella-based films improved their porosity, most likely because of effective insertion of nanoparticles into lamella stacks or in between assemblies of lamella stacks. In contrast, the crystallite size was not significantly changed, even by introducing SnO2. Because of the improvement in porosity, the composites of WO3 nanolamellae and SnO2 nanoparticles displayed enhanced sensitivity (sensor response) to NO2 at dilute concentrations of 20-1000 ppb in air, demonstrating the effectiveness of microstructure control of WO3 lamella-based films for highly sensitive NO2 detection. Electrical sensitization by SnO2 nanoparticles was also considered.

Porosity and pore size distribution measurement of cement/carbon nanofiber composites by 1H low field nuclear magnetic resonance

The dispersion effect of carbon nanofibers (CNFs) in aqueous solution and the mechanical properties, porosity, pore size distribution and microstructure of CNFs reinforced cement-based composites were investigated in this paper. To achieve effective dispersion of CNFs, a method utilizing ultrasonic processing and a commercially surfactant were employed. CNFs were incorporated to cementitious materials with the addition of 0.1 wt% and 0.2 wt% of cement with a water/cement ratio of 0.35. The mechanical properties of CNFs/cement composites were analyzed, the porosity and pore size distribution were characterized by 1H low field nuclear magnetic resonance (NMR), and the microstructure was observed by scanning electron microscopy (SEM). The results indicate that the optimum concentration ratio of MC to CNFs is 2:1 for dispersing in aqueous solution. Moreover, in the field of mechanical properties, CNFs can improve the flexural strength and compressive strength. The increased mechanical properties and the decreased porosity of the matrices correspond to the increasing CNFs content and CNFs act as bridges and networks across cracks and voids.

1D and 2D Thiazole-Based Copper(II) Coordination Polymers: Synthesis and Applications in Carbon Dioxide Capture.

The reaction of different copper(II) salts with a class of thiazole-based ligands under solvothermal conditions produces three crystalline 1D/2D coordination polymers: [Cu(κ-N-thiazole)4 (SiF6 )]∞ (1 (1D)), {Cu[μ-(κ-N:κ-COO)-L1 ]2 ⋅(H2 O)}∞ (2 (2D); HL1 =2-aminothiazole-5-carboxylic acid), and {Cu[μ-(κ-N:κ-COO)-L2 ]2 ⋅1.5 (H2 O)}∞ (3 (2D); HL2 =thiazole-5-carboxylic acid). All the materials have been characterized through common solid-state techniques: single-crystal (XRD) and (variable-temperature) powder X-ray diffraction (PXRD), infrared spectroscopy (IR), thermogravimetric analysis combined with mass spectrometry (TGA-MS), and BET surface area and pore-size distribution measurements. Polymer 3 shows a porous structure made of squared channels formed by the ordered stacking of the planar sheets along the a crystallographic axis (inner surface area equal to 15 m2 g-1 , as inferred from N2 adsorption at T=77 K on the pre-activated form), and it has been exploited for CO2 physisorption at ambient temperature (T=303 K) and pressure (p max.=920 torr). A remarkable CO2 uptake equal to 9.0 wt % was recorded under these mild conditions, thereby making the material promising for carbon dioxide capture in post-combustion flue gas, in which the key factor for a successful performance is the high chemical selectivity for CO2 over N2 .

Investigation on a novel CaO–Y2O3 sorbent for efficient CO2 mitigation

Different amounts of Y2O3 were incorporated into CaO through a sol–gel combustion method and compared with two naturally occurring sorbent and CaO derived from calcium acetate on CO2 capture performance. XRD, SEM, TEM and N2 adsorption results revealed that homogeneously dispersed Y2O3 nanoparticles notably improved the sorbent morphology, and therefore the capture performance. The carbonation rate in the fast stage was greatly enhanced via Y2O3 addition and a linear relationship was established between the maximum carbonation rate and the volume of pores with diameters less than 220nm. The sorbent containing 20wt% Y2O3 presented excellent cyclic CO2 capture capacity as well as stability. After 10 cycles it absorbed 0.57g CO2/g sorbent under mild conditions and still 0.49g CO2/g sorbent under realistic conditions, respectively. Finally, calcination conditions significantly influenced the sorption performance and sorbent structure. Combined with pore size distribution measurement, enhanced sintering and reactivation, two counteractive roles brought by CO2 addition during calcination, were elucidated.

Effects of Nanoporous Montmorillonite Types on the Separation Process of Chromium(III)

Bentonites contain a large amount of nanoporous and nanostructured montmorillonite, which is the dominant mineral determining the adsorptive properties of bentonites. In this study, the analyses of the characterization of bentonites for adsorption application include cation exchange capacity (CEC) measurements, swell index, dry screen (granulometric) analysis, x-ray diffraction (XRD), BET-BJH surface area and pore size distribution measurements, and scanning electron microscopy (SEM). The adsorption of chromium(III) from a 0.01 N Cr(III) solution using bentonites has been studied. The results showed that BNT3 and BNT2 have high CEC values of 100 and 95 mEq/100 g and swell index values of 30 and 24 mm, respectively. The high amounts of CEC and the swell index with high amount of granulometric (particles finer than 36 µm) values indicate that the amount of clay minerals (motmorillonite) is very high. Successful chromium removal efficiencies changed from 94.5% for BNT4 to 99.4% for BNT3. The maximum Cr(III) removal of adsorbents decreased in the following order: BNT3 > BNT2 > BNT5 > BNT1 > BNT4. The removal of chromium was correlated with the variation of bentonite types. This study aims at investigating the effects of different bentonite types on the removal of Cr(III) from synthetic wastewater using low-cost bentonites.

Effect of KCl on the selective catalytic reduction of NO with NH3 over vanadia‐based catalysts for biomass combustion

Effect of KCl on vanadia‐based catalysts for selective catalytic reduction of NO with NH3 was investigated by means of BET and pore size distribution measurements, XRD, XPS, FTIR, and NO reduction measurements. The catalytic activity was found to decrease rapidly with increasing the amount of KCl addition at different reaction temperatures. When the molar ratio of K/V exceeded 2.0, most of the activity was lost. The presence of KCl caused the sintering of the catalysts as well as the decrease in the amount of V atoms and the change of V valence state at the catalyst surface. Based on the analysis of physical and chemical properties of the catalysts, the KCl‐poisoning mechanism model of the vanadia‐based SCR catalysts was proposed. © 2013 American Institute of Chemical Engineers Environ Prog, 33: 390–395, 2014

Pore structure in a gold mine cemented paste backfill

The evolving pore structure of cemented paste backfill (CPB), formed from plant tailings and sand mixtures, is critical to a more thorough and complete understanding of its functionality as a support structure during mining operations. Here we employ Nuclear Magnetic Resonance (NMR) signal relaxation measurements to provide a quantitative measurement of pore size distributions in CPB samples and monitor their progression as hydration of the CBP proceeds over 28days. Three distinct, reproducible peaks are evident in the pore size distributions, which are consistent with cement regions, the bulk of the mixture and a macro-pore backbone. All peaks reduce to smaller pore sizes with hydration time and scale with sample permeability. A novel application of these scaling laws suggest that permeability is dominated by the network of macro-pores, which constitute only ∼4% of the total porosity/moisture content of the samples.

Isotropic yielding of unsaturated cemented silty sand

Unsaturated cemented soils are frequent both as designed materials and as naturally occurring layers. Both desiccation and cementation act separately as hardening mechanisms, but it is not clear how exactly their effects combine. Do they enhance one another? Are they mutually reinforcing? This study presents results from an experimental campaign aimed at answering these questions. Five different mixtures of soil (a granite saprolite) and cement (with cement contents in the range 0% to 7% on a dry weight basis) are tested in isotropic compression at four different water content levels. Initial void ratio is also controlled, using two initial compaction densities. Loading is performed at constant water content and suction is inferred from a set of water retention curves obtained from parallel psychrometric and pore-size distribution measurements. The range of yield stresses explored in this study covers almost two orders of magnitude and extends up to 7 MPa at suction values of up to 14 MPa. Both desiccation and cementation increase yield stress, but their effects are less marked when both act together, and therefore they are not mutually reinforcing.

Characterization and Surface Properties of Bentonites in the Separation Process of Iron(III)

Bentonite is an aluminum phyllosilicate, a clay consisting mainly of nanocrystalin particles of montmorillonite adsorbent. In this study, the physiochemical analyses of cation exchange capacity (CEC) measurements, methylene blue index (MBI), and characterization of bentonites for separation applications are examined. Some characterizations of bentonite particles such as surface properties were examined by scanning electron microscopy (SEM), x-ray diffraction (XRD), x-ray fluorescence (XRF), and Barret-Johner-Halenda (BJH) pore size distribution measurements. The adsorption of Fe(III) from a 0.01 N solution using bentonites has also been studied. The result showed that the amount of clay minerals (motmorillonite) is very high in sample A2 (from deposits of Toroud, Semnan Province of Iran). Results also show the MBI and CEC along with montmorillonite content were effective parameters on Fe(III) separation. Iron separation with removal efficiency of 52% for sample A1 (from deposits of Toroud, Semnan Province of Iran) is due to the difference in surface active doners (like O), silica entities with more homogeneous surface negative charge, interaction forces, and CEC.

A Phenomenological Interpretation of Two-Step Adsorption Kinetics of Humic Acids on Zeolitic Tuff

In this study, the kinetics of adsorption of humic acid (HA) from aqueous solution onto a zeolitic tuff were investigated. X-ray diffraction, scanning electron microscopy, porosity and pore-size distribution measurements indicate that macromolecules can diffuse into the material. The kinetic curves show a two-stage adsorption. The adsorbed amount increases up to 2 days, remains constant and then increases again to attain equilibrium. There is a remarkable similarity between this adsorption behaviour of HA on zeolitic tuff and the behaviour observed when ultrathin multi-layers of polymeric materials are fabricated by self-assembly technique. Experiments reveal two distinct stages: the first corresponds to the macromolecules being driven towards the substrate, while the second is the result of arrangement of macromolecules. The first stage is a first-order kinetics with characteristic lifetime of 1-2 days, whereas the second stage is a Johnson-Mehl-Avrami function with (tm) in the exponential and slower cha...

The influence of different carbon sources in the carbothermal reduction and nitridation (CRN) synthesis of SiAlON from nanocomposite precursors based on Al–SBA-15

Abstract Nanocomposites of Al–SBA-15 with the organic polymers poly-4-vinyl pyridine (P4VP) and polyacrylamide (PAM) were synthesized to produce SiAlON precursors containing various carbon contents. These CRN precursors, and their products after firing under N 2 at 1450 °C for 3 h were investigated by XRD, SEM/EDS and surface area analysis (BET) to compare the influence of the organic polymer carbon source. The results were also compared with those from precursors containing carbon black as the carbon source. XRD and SEM/EDS analysis of the Al–SBA-15 confirmed the formation of mesoporous structures, while BET and pore size distribution measurements indicated that the entry of P4VP into the Al–SBA-15 nanocomposite precursor is significantly more efficient than that of PAM. Firing these precursors in nitrogen produced β-SiAlON and β-cristobalite. At all carbon concentrations the P4VP nanocomposite precursors formed significantly more SiAlON than those of the PAM and carbon black precursors, due to the proximity of a greater amount of the organic carbon source to the silica template in the P4VP composite, and possibly also to the lack of oxygen in the P4VP monomer, in contrast with PAM. At least twice the stoichiometric amount of carbon was required in all cases, with optimal SiAlON formation occurring in the P4VP precursor containing 6 times the stoichiometric amount of carbon. Increasing the carbon content further suppresses SiAlON formation, possibly due to the build-up of back pressure of CO by-products in the pores of the nanocomposite.

日本海東縁海底下に分布する砂層の孔隙特性と年代 : MD179航海

In 2010 the MD179 project was undertaken aiming at recovery of deep seated gas hydrate, methane induced carbonate, and deep sediments older than 300 ka. Sediment samples were obtained in the Umitaka Spur, Joetsu Channel, Toyama Trough, Japan Basin, Nishi Tsugaru and Okushiri Ridge areas. Small amounts of sandy sediment have been retrieved as thin intercalations in Pleistocene and Holocene muddy layers, where trace fossils and strong bioturbations are commonly observed.Those sandy sediments consist of very fine- to fine-grained sand grains, and are sometimes tuffaceous. Pore-size distribution measurements and thin-section observations of these sands were undertaken, which indicated that porosities of muddy sediments are around 50 % but those of arenites range from 42 to 52%. Mean pore sizes and permeabilities of those arenites are larger than those of mudstones. While the presence of gas hydrate in intergranular pores of sands has not been confirmed, the soupy occurrence in recovered sediments may strongly indicate the presence of hydrate filling the intergranular pore system of sands. Such arenites have been recognized till now in the Mallik, NW Territory Canada, as well as in the Nankai Trough areas, which are expected common even in the subsurface sandy sediments at the eastern margin of Japan Sea. Concentration of gas hydrate may need primary intergranular pores large enough for gas hydrate to occur within host sediments likely deposited in the sedimentary environment such as deep sea channels. Small amounts of sandy sediment were retrieved as thin intercalations in Pleistocene silty layers, because supplying sediments may not be abundant due to sea level fluctuation during Pleistocene ice age. As time of deposition of coarse-grained sediments can be recognized by the thermoluminescence (TL) dating method, sandy sediments are usually tuffaceous and contain a small amount of quartz grains, and TL dating has been completed only for seven samples, which indicate 48 to 980 ka in age. This study was performed as a part of the MH21 Research Consortium.

Recycling of Solid Waste Material In Hong Kong: I. Properties of Modified Clay Mineral Waste Material and its Application for Removal of Cadmium In Water

Large quantities of solid waste are disposed to landfill sites in Hong Kong each year and these landfill sites will be filled within five years. Recycling of solid waste material has become a very urgent task and evaluation of its application in environmental remediation has been functioned recently. Mineral-containing waste material, which is one of the common solid waste components to be disposed to landfill sites in Hong Kong, was used to produce the modified clay mineral waste material (MCMWM) for removal of cadmium (Cd) in water. The physical, chemical and mineralogical properties of MCMWM related to Cd adsorption were investigated using scanning electron microscopy (SEM) coupled with energy dispersive X-ray analysis (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), BET specific surface area (SSA) and pore size distribution (PSD) measurements, and inductively coupled plasma optical emission spectroscopy (ICP-OES). The particle size of MCMWM ranged from less than a few to tens of micrometers, and the particles had rough surface and structural defects. Specific surface area was 5.6 m2/g, with different types of external and internal pores being observed. The minerals in MCMWM were mainly 2:1 clay minerals. Smectite, illite, chlorite, feldspars, quartz, and calcium hydroxide were detected. Heavy metals including arsenic, cadmium, chromium, mercury and lead detected in MCMWM were much lower than the maximum allowed level for each kind of heavy metal based on the Dutch Standard that has been used worldwide. Cadmium adsorption by MCMWM was very rapid in solid/liquid interface as up to 90% of Cd2+ can be adsorbed within half hour of reaction. The amount of Cd2+ adsorbed increased but the rate of adsorption decreased with increasing concentration of Cd2+ in solution. The Cd2+ adsorption was related to the surface structure and chemistry, including SSA, PSD, surface defect, charge and bonding in MCMWM.

Characterisation, phase stability and surface chemical properties of photocatalytic active Zr and Y co-doped anatase TiO2 nanoparticles

We report on the characterization, phase stability, surface chemical and photocatalytic properties of Zr and Y co-doped anatase TiO2 nanoparticles prepared by homogenous hydrolysis methods using urea as precipitating agent. The materials were analyzed by scanning electron microscopy, X-ray diffraction, Raman spectroscopy, BET isotherm and BJH pore size distribution measurements. It is shown that Y and Zr ions replace Ti ions in the anatase TiO2 structures up to a critical total dopant concentration of approximately 13wt%. The co-doped particles show increased phase stability compared to pure anatase TiO2 nanoparticles. The anatase to rutile phase transformation is shown to be preceded by cation segregation and dissolution with concomitant precipitation of Y2Ti2−xZrxO7 and ZrTiO4. Co-doping modifies the optical absorption edge with a resulting attenuation of the Urbach tail. The band gap is slightly blue-shifted at high doping concentrations, and red shifted at lower doping concentrations. Formic acid adsorption was used as a probe molecule to investigate surface chemical properties and adsorbate structures. It was found that the relative abundance of monodentate formate compared to bidentate coordinated formate decreases with increasing doping concentration. This is attributed to an increased surface acidity with increasing dopant concentration. Photodegradation of formic acid occurred on all samples. With mode-resolved in situ FTIR spectroscopy it is shown that the rate of photodegradation of monodentate formate species are higher than for bidentate formate species. Thus our results show that the trend of decreasing photo-degradation rate with increasing dopant concentration can be explained by the adsorbate structure, which is controlled by the acidity of the surface.