Wide Pore Size Research Articles

Adsorptive removal of humic acid from aqueous solution by micro- and mesoporous covalent triazine-based framework

Abstract The presence of humic acid (HA) in aquatic environments causes potential human health and biological instability. We synthesized micro- and mesoporous covalent triazine-based framework (CTF) and further conducted batch experiments to systematically examine its adsorption properties toward HA. The adsorbent was characterized by a variety of experimental and spectroscopic techniques with respect to structural, porosity and surface characteristics. Additionally, the mesoporous CTF showed faster adsorption kinetics of HA, which was attributed to its shaped, open and wide pore size distribution. Findings of the present work highlight the potential of using synthesized mesoporous CTF as promising adsorbent for the removal of HA, particularly for the bulky molecular compounds, from aqueous solution.

Hydrophobicity of amorphous silica-based inorganic-organic hybrid materials derived from perhydropolysilazane chemically modified with alcohols

Perhydropolysilazane (PHPS) was chemically modified with various alcohols (ROH, RCH3, n-C3H7, n-C5H11, n-C10H21, CH3OC2H4 or C2H5OC2H4) at a PHPS (Si basis) to ROH molar ratio of 3:1. The resulting alkoxy group-functionalized PHPS materials were successfully converted to amorphous silica-based inorganic-organic hybrids by exposure to vapour from aqueous ammonia at room temperature. Nitrogen sorption analyses demonstrated that these hybrids contained a small quantity of micropores less than 0.9 nm in size along with mesopores having a relatively wide pore size distribution (PSD). The PSD plots of the CH3O, CH3OC2H4O and C2H5OC2H4O functionalized samples had especially wide distributions extending to more than 50 nm. Water sorption tests showed that the hybrid synthesized from PHPS modified with n-C10H21OH was stable and did not exhibit significant capillary condensation even at higher levels of humidity above P/Po = 0.6. As a result, the number of water molecules adsorbed per square nanometre of the sample surface area at P/Po = 0.95 was as low as 4 mol nm−2. The relatively low density of hydrophilic silanol groups (0.21), smaller average mesopore size (3.3 nm) and longer hydrophobic alkyl chain of the n-C10H21O moiety were all thought to contribute to improving the hydrophobicity of this hybrid. These results indicate that n-C10H21OH is a useful alcohol modifier for synthesizing amorphous silica-based inorganic-organic hybrid materials with improved hydrophobic properties through a polymer precursor route.

Petrophysical characterization of tight oil reservoirs using pressure-controlled porosimetry combined with rate-controlled porosimetry

Abstract Tight oil reservoirs typically show a wide pore size distribution with pore sizes ranging from several nanometers to several hundred microns, requiring a combination of several techniques to properly characterize the pore structures. In this paper, scanning electron microscopy, pressure-controlled porosimetry and rate-controlled porosimetry were applied to investigate the pore systems of a tight sandstone oil reservoir in Ordos Basin, Northern China. Pores were identified and classified by scanning electron microscopy; pore size distribution was calculated by pressure-controlled porosimetry and rate-controlled porosimetry; main pore sizes were clarified and an empirical permeability estimation model is proposed by extending Winland’s work. Results indicate that four types of pores exist in tight sandstone oil reservoirs, which are residual interparticle pores, grain dissolution pores, clay dominated pores and micro fractures. A combination of pressure-controlled porosimetry and rate-controlled porosimetry is proposed as a new method to obtain the overall pore size distribution of tight oil reservoirs with pore radii ranging from 9.2 nm to 500 μm. The overall pore size distribution of tight oil reservoirs is polymodal; pores with radii ranging between 80 and 500 μm and distributed around the right peak are composed of residual interparticle pores, while the left peaks show fluctuation because of complexity in pore types and the multi-scale porosity of clays. The average mercury intrusion saturation of the nanopores is 66.50% and that of mesopores is 24.16%. The nanopores and mesopores are considered to be the main pore types. The new permeability estimation equation indicates a throat radius corresponding to 30% mercury saturation is the dominant throat radius, and shows suitable estimation of permeability with an R2 value of 0.95542. The proposed method is effective in obtaining the overall pore size distribution of the tight oil reservoirs, and can further be used for storage capacity evaluation and better permeability estimation.

Adsorption dynamics of hydrogen and deuterium in a carbon molecular sieve bed at 77 K

The adsorption equilibrium and rate of H2 and D2 on a Carbon Molecular Sieve (CMS) with wide pore size distribution were measured at 77K using a volumetric method. The adsorption equilibrium or kinetic ratios for D2 to H2 decreased with increasing pressure. The adsorption uptake curve showed a slow adsorption rate with time after displaying a fast adsorption rate in the initial period. Adsorption rate constants of D2 were larger than those of H2 at low pressure, and the ratio of D2 to H2 decreased with an increase in pressure. However, in breakthrough experiments for dynamic separation efficiency of hydrogen isotope separation, the CMS showed higher breakthrough separation factors than the corresponding adsorption equilibrium or kinetic ratios. The breakthrough separation factor reached 1.53 at a total gas pressure of 400.0kPa and a flow rate of 129.8cm3/min in the adsorption bed length of 1.0m. In addition, the shape of D2 breakthrough curve was slightly affected by the change of flow rate, but that of H2 breakthrough curve showed almost constant pattern. And meso and macropores of the CMS gave a negative effect on the separation of H2 and D2. Therefore, the key factor in separating H2 and D2 from the mixture depended not only on their equilibrium selectivity but also on their dynamic diffusional difference in the CMS bed due to the quantum molecular sieving effect in space-limited pore at low temperature.

High-pressure synthesis of mesoporous stishovite: potential applications in mineral physics

Recently, we have described a successful synthesis route to obtain mesoporous quartz and its high-pressure polymorph coesite by nanocasting at high pressure using periodic mesostructured precursors, such as SBA-16 and FDU-12/carbon composite as starting materials. Periodic mesoporous high-pressure silica polymorphs are of particular interest as they combine transport properties and physical properties such as hardness that potentially enable the industrial use of these materials. In addition, synthesis of mesoporous crystalline silica phases can allow more detailed geology-related studies such as water/mineral interaction, dissolution/crystallization rate and the surface contribution to the associated thermodynamic stability (free energy and enthalpy) of the various polymorphs and their crossover. Here, we present results of synthesis of mesoporous stishovite from cubic large-pore periodic mesoporous silica LP-FDU-12/C composite as precursor with an fcc lattice. We describe the synthesis procedure using multi-anvil apparatus at 9 GPa (about 90,000 atm) and temperature of 500 °C. The synthetic mesoporous stishovite is, then, characterized by wide and small-angle X-ray diffraction, scanning/transmission electron microscopy and gas adsorption. Results show that this new material is characterized by accessible mesopores with wide pore size distribution, surface area of ~45 m2/g and volume of pores of ~0.15 cm3/g. Results from gas adsorption indicate that both porosity and permeability are retained at the high pressures of synthesis but with weak periodic order of the pores.

Bridged mesoporous silsesquioxanes as potential CO2 adsorbents

Mesoporous amino-functionalized adsorbents for post-combustion CO2 capture were synthesized by grafting and sol-gel methods. The silsesquioxane obtained by polycondensation of bis(3-(trimethoxysilyl)-propyl)a- mine without a cross-linker had the highest amount of surface amino groups. Their content was 8.4 times higher than in the grafted material prepared with the same pre- cursor. All obtained materials were tested in CO2 reversible adsorption from a gas stream. The bridged silsesquioxane adsorbent had the adsorption capacity 4.7 times higher than the grafted sample obtained from the same precursor. Porosity study of this material revealed wide pore size distribution with notable fraction of macropores. The na- ture of adsorbed species was determined from the FTIR spectrum after adsorption. It was found that CO2 formed carbamate and bicarbonate species on the surface. Graphical Abstract

Characterization of free thiol variants of an IgG1 by reversed phase ultra high pressure liquid chromatography coupled with mass spectrometry

RP-HPLC has been demonstrated as a powerful tool to study antibody free thiol and disulfide variants. Recently, the introduction of UHPLC columns with wide pore size (300Å) and small particle size (1.7μm) offered the opportunity to further improve the separation of such variants. This paper describes a systematic evaluation of stationary phases, operating parameters, and mobile phases for a UHPLC based method to separate free thiol variants of a recombinant monoclonal antibody (referred as mAb A), targeting high resolution, high throughput and improved recovery. Among the four different stationary phases evaluated, UHPLC diphenyl columns were found to provide the best separation. Using an optimized UHPLC method, free thiol variants of mAb A were separated in 5min. Importantly, the UHPLC method revealed minor variants that had coeluted in an HPLC based method, and the UHPLC method is also applicable as a platform method for characterization of other mAbs as well. Furthermore, an on-line UHPLC–MS method was developed to characterize the separated variants, and this method can streamline the characterization of fully assembled monoclonal and bispecific therapeutic antibodies.

The power of power: Electrokinetic control of PAH interactions with exfoliated graphite

Exfoliated graphite (EG) exhibits exceptional sorption capacity for petroleum and dissolved hydrocarbons owing to its highly hydrophobic surface and wide pore size distribution. The high price of preparing EG, however, restricts its application. Methods which increase the rate or extent of sorption to EG even further are thus longed for. Here, we assess the effects of weak direct current (DC) fields on the sorption of the polycyclic aromatic hydrocarbon phenanthrene (PHE) to EG. DC applied to an ionic solution in a solid matrix invokes electroosmotic flow (EOF), i.e., the surface charge-induced movement of the solution. EG was exposed to weak DC fields in the presence of dissolved PHE to test if EOF increases transport of PHE to poorly accessible sorption sites. DC fields increased PHE sorption rates in EG sevenfold and reduced the desorption rate of sorbed PHE by >99%. EOF thus appeared to be highly effective in translocating PHE into pores, which contribute most of the sorption sites, but are difficult to access in the absence of EOF by molecular diffusion only. The observed ‘power of power’ may be used to kinetically regulate the interaction of sorbates with EG or other porous sorbents in environmental (bio-) technology.

PORE STRUCTURE CHARACTERIZATION OF CHEMICALLY MODIFIED BIOCHAR DERIVED FROM RICE STRAW

Biochar derived from agricultural biomass waste is increasingly recognized as multifunctional material for various applications according its characteristics. It is therefore essential to investigate biochar properties before large-scale application. In this study, rice straw-derived biochars produced at different temperature (550, 650, 750 oC). The resulting biochars were subjected to liquid-phase oxidation by different agents including KOH, HNO3, H2SO4, H2O2 and KMnO4 to obtain biochar with different properties. Pore structure characteristics including surface area, micro and meso pore volume, and pore size distribution were studied. Biochar surface is sensitive to the type of modifying reagent. Biochars treated by KOH, KMnO4 and H2O2 give higher nitrogen uptake in the range of micropores and mesopores. The rice straw-derived biochars especially produced at 650oC and treated by KOH have the highest surface area (179.7 m2/g) and micropore volume (0.081 cc/g) than the rest of biochars. In contrast, biochars treated by H2SO4 and HNO3 give lower nitrogen uptake and lead to loss of the biochars porosity. Loss of micropore volume is as low as 10-40% of pore volume in H2SO4 and HNO3 treated biochars. Biochars exhibit wide pore size distribution, from narrow micropores to wide mesopores. One modal distribution was obtained with peak oscillate in region of 1.0 to 1.3 nm in the case of micropore region. However, for mesopore region, two minima at about 3.0 nm and 5.0 nm were observed. More homogonous micropore distribution was produced from KOH and H2O2 treatment in contrast to that of HNO3 and H2SO4 treatment, which give heterogeneous micropore distribution.

Facile simulation of carbon with wide pore size distribution for electric double-layer capacitance based on Helmholtz models

Incorporation of surface-based capacitances (C/S) simulated by Helmholtz models with pore size distribution obtained from the non-local density functional theory precisely predicts the double-layer capacitance of distinct forms of carbon.

Fast diffusion supercapacitors via an ultra-high pore volume of crumpled 3D structure reduced graphene oxide activation

In order to obtain a high performance supercapacitor, our a-NSrGO for crumpled 3D structure graphene maintains a high specific surface area and total pore volume with a wide pore size distribution, leading to the fast diffusion rate of electrolyte ions.

The effect of analytical particle size on gas adsorption porosimetry of shale

Gas storage capacity and gas producibility of shale gas reservoirs are critically limited by shale porosity. In spite of its importance, porosimetric characterization of shale remains challenging due to highly heterogeneous structures, small average pore sizes, and wide pore size distributions. This study utilizes low-pressure N2 and CO2 gas adsorption porosimetry to investigate the evolution of micro- and mesopores in a suite of 11 New Albany Shale samples across a wide range of thermal maturity corresponding to vitrinite reflection Ro values from 0.35 to 1.41%. Mesopore volumes follow a nonlinear evolutionary path starting with a maximum in immature shale (sample 472-1). Subsequent intermittent minima in mesopore volumes during early and late maturity are consistent with the transformation of kerogen during the early mature stage (sample 554-2) and secondary cracking of bitumen/oil at the late mature stage (sample IL2), respectively. Micropore volumes display a varying trend throughout thermal maturation, and are significantly controlled by total organic carbon contents. Both meso- and micropore volumes are positively correlated with clay content and tend to decrease with an increase in feldspar content.A reduction in grain size of shale samples for gas adsorption porosimetry prominently enhances mesopore volumes, whereas the effects on micropore volumes are variable. These findings may be associated with the fact that smaller particles are able to attain complete adsorption equilibrium quickly, which in turn reduces experimental artefacts during gas adsorption porosimetry. Crushing of shale not only alters the shape of gas adsorption hysteresis loops, but also tends to tighten the openings of hysteresis loops by enhancing the connectivity of pores and reducing the likelihood of gas being trapped during desorption.

Adsorption of Polychlorinated Dibenzo-p-Dioxins and Dibenzofurans Vapors on Activated Carbon

Activated carbon (AC) adsorption is an important method to control the emission of dioxins and dioxin-like congeners (polychlorinated dibenzo-p-dioxins and dibenzofurans [PCDD/Fs] and polychlorinated biphenyls [PCBs]), of other semi-volatiles (such as Polycyclic Aromatic Hydrocarbons) and heavy metals (mainly mercury) arising from municipal waste incineration and other effluents. Investigating the adsorption characteristics of AC for PCDD/Fs allows selection of the best AC types, to meet the new and more stringent PCDD/F emission standards. In this study, the adsorption of dioxins on three kinds of commercial AC was evaluated through three bench-scale experiments. A dioxin generator was applied to generate a PCDD/Fs containing gas stream with constant concentration. Physical properties of AC, including its density, Brunauer–Emmet–Teller–surface, pore volume, and pore size distribution, were considered. The results show that the removal efficiencies of PCDD/Fs correlate more strongly with pore volume (r2>0.93) than with the surface area (r2<0.48). Among the three types of AC tested, the coconut shell sample with wide pore size distribution reached the highest adsorption efficiency. Under the testing conditions used, the total removal efficiency reached over 96%, much more than the 81.7% efficiency achieved by lignite AC. In addition, the selectivity of lignite AC for 17 toxic PCDD/F congeners is distinct from the two other samples.

Characterizing soil pore structure using nitrogen adsorption, mercury intrusion porosimetry, and synchrotron-radiation-based X-ray computed microtomography techniques

Purpose Soils have a wide range of pore size distribution (PSD) from nanometer to micrometer scale. The detailed characterization of soil pore structure in a wide pore size range is important for understanding the soil processes. In this study, three different techniques are used to quantitatively describe the soil pore characteristics in a wide pore size range and to evaluate whether different pedogenic processes affect porosity and PSD of the soils.

Fluctuations of the number of neighboring pores and appearance of multiple nonergodic states of a nonwetting liquid confined in a disordered nanoporous medium

Abstract Multiple nonergodic states have been observed for nonwetting liquid in the Fluka100 C18 and Fluka100 C8 porous media with broad pore size distributions having different widths. The dispersion transition where the volume of confined liquid depends critically on the degree of filling of the porous medium and temperature is observed in the temperature range 293–343 K under study for the Fluka100 C18 porous medium and is not observed for the Fluka100 C8 porous medium. A mechanism of the appearance of multiple nonergodic states has been proposed. It has been shown that fluctuations of the number of the nearest neighbors in the disordered system are mainly responsible for the features of confinement of nonwetting liquid and nonergodic states of nonwetting liquid in the nanoporous media under investigation with wide pore size distributions.

Promontofixation : quelles prothèses choisir ? Étude expérimentale et clinique

BackgroundSacrocolpopexy is the standard surgical treatment of genital prolapse of the upper vaginal wall. Nowadays, the laparotomy approach is progressively supplanted by the laparoscopic procedure for the same anatomical results. About sacrocolpopexy, to date it still remains details of the technique, which differ with surgical teams maintaining controversy. Among them, the choice of the meshes certainly creates debate. ObjectivesTo state the basic physicochemical principles which are necessary for surgeons to select the most suitable prosthetic material to obtain the most beneficial anatomic and functional outcomes for patients. Material and methodsThe concepts of prosthetic biocompatibility, strength, shrinkage, deformation and elasticity are discussed. They are illustrated by experimental animal references and also human clinical references. ResultsMacroporous polypropylene and polyester prostheses (pore size>1mm) are properly integrated. Collagen prosthetic coating improves tissue integration. Absorbable and nonabsorbable ultralight prostheses expose patients to a high risk of recurrence. Multifilament polyester wide pore-side prostheses have less retraction and are more flexible than monofilament polypropylene prostheses. Discussion and conclusionThe prosthetic cut-off weight below which the mesh does not offer any guarantee of strength is not precisely known. Moreover, the benefit of weight reduction is not proved. Currently, heavy weight multifilament polyester prostheses with wide pore size, more than 1mm, appear to be the most appropriate meshes for sacrocolpopexy without vaginal incision.

Determination of the pore size distribution of high-performance liquid chromatography stationary phases via inverse size exclusion chromatography

Stationary phases in liquid chromatography exhibit quite different pore structures. Whereas most of the fully porous packing materials possess a narrow pore size distribution, core–shell particles are usually of rather wide pore size distribution. Recently a novel theory of size exclusion chromatography was introduced to model the effect of pore size distribution. The molecular theory of chromatography allows taking into account the kinetics of the pore ingress and egress processes, the heterogeneity of the pore sizes and polymer polydispersity as well. The novel model was applied to inverse size exclusion chromatography data. In this study, we have determined the actual pore size distribution of a number of HPLC stationary phases. Our results agree well with the results obtained with the model introduced by Knox and Scott.

Sponge‐Templated Preparation of High Surface Area Graphene with Ultrahigh Capacitive Deionization Performance

Capacitive deionization (CDI) is a competent water desalination technique offering an appropriate route to obtain clean water. However, a rational designed structure of the electrode materials is essentially required for achieving high CDI performance. Here, a novel sponge‐templated strategy is developed for the first time to prepare graphene sheets with high specific surface area and suitable pore size distribution. Sponge is used as the support of graphene oxide to prevent the restack of graphene sheets, as well as to suppress the agglomerate during the annealing process. Importantly, the as‐fabricated graphene sheets possess high specific surface area of 305 m2 g−1 and wide pore size distribution. Ultrahigh CDI performance, a remarkable electrosorptive capacity of 4.95 mg g−1, and siginificant desorption rate of 25 min, is achieved with the sponge‐templated prepared graphene electrodes. This work provides an effective solution for the synthesis of rational graphene architectures for general applications in CDI, energy storage and conversion.

Molecular theory of size exclusion chromatography for wide pore size distributions

Chromatographic processes can conveniently be modeled at a microscopic level using the molecular theory of chromatography. This molecular or microscopic theory is completely general; therefore it can be used for any chromatographic process such as adsorption, partition, ion-exchange or size exclusion chromatography. The molecular theory of chromatography allows taking into account the kinetics of the pore ingress and egress processes, the heterogeneity of the pore sizes and polymer polydispersion. In this work, we assume that the pore size in the stationary phase of chromatographic columns is governed by a wide lognormal distribution. This property is integrated into the molecular model of size exclusion chromatography and the moments of the elution profiles were calculated for several kinds of pore structure. Our results demonstrate that wide pore size distributions have strong influence on the retention properties (retention time, peak width, and peak shape) of macromolecules. The novel model allows us to estimate the real pore size distribution of commonly used HPLC stationary phases, and the effect of this distribution on the size exclusion process.

Synthesis of an organic conductive porous material using starch aerogels as template for chronic invasive electrodes

We report the development of an organic conducting mesoporous material, as coat for invasive electrodes, by a novel methodology based on the use of starch aerogel as template. The poly(3,4-ethylenedioxythiophene) (PEDOT) aerogel was synthesized by polymerization of 3,4-ethylenedioxythiophene within a saturated starch aerogel with iron (III) p-toluenesulfonate (oxidizing agent) and subsequent removal of the polysaccharide template, followed by supercritical CO2 drying. The chemical structure and oxidation state of the resulting material were studied by Raman spectroscopy. The morphology and surface properties of the obtained nanoporous material were investigated by scanning electron microscopy (SEM), micro computed tomography (μCT) and nitrogen adsorption–desorption techniques. The composition and thermal behaviour were evaluated by energy dispersive spectroscopy (EDS) and thermogravimetric analysis (TGA) respectively. A preliminary biocompatibility test verified the non-cytotoxic effects of the PEDOT aerogel. The large surface area and wide pore size distribution of the PEDOT conductive aerogel, along with its electrical properties, enable it to be used as extracellular matrix scaffold for biomedical applications.