Amount Of Specific Surface Area Research Articles

Effect of particle size on CO adsorption and thermodynamic analysis

The liquid nitrogen adsorption method was used to characterize the pore structure of non-cohesive coal in the 061,404 working face of the Lingxin coal mine. The amount of specific surface area of micropores in the sample continuously rose as particle sizes reduced. The volumetric method was used to measure the CO isothermal adsorption curves of three samples (sample I, 0.425–0.25 mm, sample II, 0.18–0.25 mm, and sample III, 0.15–0.18 mm). The experimental results were fitted by the Langmuir model. According to the experimental results, it was conducive to CO adsorption with the conditions of high pressure and low-temperature. The decrease in grain diameter increased the number and volume of micropores in the sample, which improved the adsorption capacity of the sample. In addition, according to the adsorption data, the CO adsorption thermodynamics of three samples were analyzed, including surface potential (Ω), Gibbs free energy change (ΔG) and entropy change (ΔS). The results demonstrated that CO adsorption by coal was a spontaneous process. Sample III has the most substantial adsorption capacity, whereas the sample I has the weakest adsorption capacity.

Biomechanical behavior of diamond lattice scaffolds obtained by two different design approaches with similar porosity; a numerical investigation with FEM and CFD analysis.

Scaffolds provide a suitable environment for the bone tissue to maintain its self-healing ability and help new bone-cell formation by creating structures with similar mechanical properties to the surrounding tissue. In the modeling of the scaffolds, an optimum environment is tried to be provided by changing the geometrical properties of the cell architecture such as porosity, pore size, and specific surface area. For this purpose, different design approaches have been used in studies to change these properties. This study aims to determine whether scaffolds with similar porosities modeled by different design approaches exhibit distinct biomechanical behaviors or not. By using the Diamond lattice architecture, two different design approaches were constituted. The first approach has constant wall thickness and variable cell size, whereas the second approach contains variable wall thickness and constant cell size. The usage of different design approaches affected the amount of specific surface area in models with similar porosity. Mechanical compression tests were conducted via finite element analysis, while the permeability performance of configurations with similar porosities (50%, 60%, 70%, 80%, and 90%) was evaluated by using computational fluid dynamics. The mechanical results revealed that the structural strength decreased with increasing porosity. Since their higher specific surface area causes lower pressure drops, the second group exhibits better permeability. In addition, it was found that to evaluate the wall shear stresses occurring on the scaffold surfaces properly, it is essential to consider the stress distributions within the scaffold rather than the maximum values.

Preparation of clinoptilolite/starch/CoFe2O4 magnetic nanocomposite powder and its elimination properties for cationic dyes from water and wastewater

A new magnetic nanocomposite clinoptilolite (CLT)/Starch/CoFe2O4 was synthesized using co-precipitation method. The prepared magnetic composite powder was utilized for decontamination of methylene blue dye (MBD), methyl violet dye (MVD), and crystal violet dye (CVD) from water media. The BET analysis showed that CLT modification using starch and CoFe2O4 nanoparticles improved its specific surface and the amount of specific surface area for CLT, CoFe2O4, and CLT/Starch/CoFe2O4 powder was reported to be 18.82 m2.g−1, 151.4 m2.g-1, and 104.75 m2.g−1, respectively. Experimental results showed that pH 9 had a vital role in the adsorption process of all three types. Langmuir and Redlich-Petersen isotherm models were well fitted with experimental data. Also, the maximum adsorption capacity of CVD, MBD, and MVD to the desired composite was determined as 32.84 mg.g−1, 31.81 mg.g−1, and 31.15 mg.g−1, respectively. In addition, the kinetic data of the removal process followed a pseudo-first order (PFO) kinetic model. Negative thermodynamic parameters were indicated that the process is spontaneous and exothermic. Finally, ad(de)sorption experiments' results showed that the synthesized nanocomposite adsorbent has an excellent ability to adsorb cationic dyes after several consecutive cycles.

Hydrogen isotope effect of nanoporous palladium

Materials used in hydrogen isotopes separation are crucial in modern hydrogen energy field. In this article, a promising material nanoporous palladium was prepared and its relative properties were studied. Nanoporous palladium with pore scale of about 5 nm was fabricated by free dealloying corrosion. Its kinetic and PCT curves of hydrogen/deuterium adsorption at room temperature were tested using a Sievert-type volumetric apparatus. Microstructures were observed with Scanning Electron Microscopy and Atomic Force Microscopy. Crystalline structure was characterized with X-Ray Diffractometer before and after deuterium adsorption. Comparative experiments with spongy palladium that is commonly used in relative industry were also carried out. According to the results, nanoporous palladium shows faster hydrogen/deuterium adsorption rate than spongy palladium, which is due to its nanoporous structure that supplies a large amount of specific surface area. PCT curves of hydrogen/deuterium adsorption in nanoporous palladium among 298–338 K were tested and plateau pressures at different temperatures were obtained. Deuterium/hydrogen isotopes separation factors were calculated using plateau pressures above and were plotted with temperature. It's found that nanoporous palladium shows larger hydrogen isotope separation factors compared with spongy palladium at temperatures no higher than 323 K. These findings illustrate that nanoporous palladium would be an ideal material for hydrogen isotopes separation applications.

Selection of carbon materials and modification methods in low-temperature sintering flue gas denitrification

Carbon materials have shown excellent low temperature denitrification characteristic in the flue gas. To improve the denitrification efficiency, metallurgical coke, biomass char and semi-coke were modified by steam or acid. Taguchi experimental design was used to determine the influence of carbon material type, modified time and process temperature etc. on the denitrification rates. Three carbon materials before and after modification were characterized by SEM, BET and FTIR. The results showed that a large amount of specific surface area and smaller pore size were beneficial for NOx removal with NH3, but the surface acidic functional groups were crucial for denitrification. For steam modification, the optimal promotion of denitrification rate was semi-coke, modified by steam at 973K for 140min and the nitrogen oxides removal rate was 16.0%. For acid modification, the optimal combination was biomass char, with the deashing acid treatment before oxidation acid treatment at 353K and the nitrogen oxides removal rate was 24.0%.

The formation of ultralow-density microcellular diane-formaldehyde gels and aerogels

A diane–formaldehyde aerogel is synthesized via a new two-step approach consisting of the sol–gel polycondensation of diane and formaldehyde. The first stage affords individual polymethylol phenols; at the second stage, these are cured in an alkaline solution at 225°С via the introduction of an additional amount of formaldehyde. The diane–formaldehyde gel is isolated for the first time from the initial solution at a minimum possible concentration of gel formation of 1 mg/mL. The aerogel is obtained during supercritical drying of the diane–formaldehyde gel. The density of the ultralow-density microcellular aerogels reaches 10.9 mg/cm3, and their specific surface area amounts to 340–716 m2/g. The features, structures, and properties of the resulting diane–formaldehyde gels are studied.

Characterizing the pore structure in the Silurian and Permian shales of the Sichuan Basin, China

Nitrogen sorption and mercury intrusion methods were applied to characterize the pore structure of the Lower Silurian shales of the Long-ma-xi Formation and Upper Permian shales of the Da-long Formation in the Sichuan Basin. The results indicate that the specific surface areas and porosities of the Silurian shales are in the range of 17.83–29.49 m2/g and 3.65–18.26%, respectively. The Silurian shales show a bimodal pore-size distribution, and consist of both micropores and nanopores, ranging from 30 to 60 μm and 1.7–20 nm, respectively. A strong positive linear correlation between the surface areas and total organic carbon content (TOC) suggests that the organic matter contributes mostly to the amount of specific surface area of the Silurian shales, whereas the contribution of clay minerals appears to be negligible. The organic matter also accounts for 50–70% of the porosity in the Silurian shales. Soluble organic matter in the form of bitumen, however has a negative impact on the surface area and porosity of the Silurian shales and reduce the amount of surface area and porosity in these shales. For the Permian shales, their surface area and porosity are lower than those of the Silurian shales, and are in the ranges of 2.20–3.52 m2/g and of 1.30–4.15%, respectively. The pore-size distribution of the Permian shales shows a unimodal pattern of micropores in a size range of 30–60 μm. Their TOC and clay mineral contents display poor correlation with the surface areas and suggest that both the organic matter and clay minerals have very low surface areas. A clear negative correlation between the porosity and TOC in the Permian shales indicates that organic matter contributes little or insignificantly to the porosity due to poorly developed organic pores in kerogen because the Permian shales are much lower in thermal maturity than the Silurian shales. Furthermore, there is a consistent negative linear correlations between the bitumen content and the porosity for both the Permian shales and Silurian shales and indicate that the bitumen may significantly reduce the porosity of the shales by occupying the pore spaces in the mineral and organic matrix. Finally, it is clear that the Lower Silurian shales have a greater shale gas potential than the Upper Permian shales do based on their surface area and porosity.

Determining the size distribution-defined aspect ratio of platy particles

Mineral particles are used in many industrial applications as fillers, in coatings, as ad- and absorbers or in catalysis. In these manifold fields the particle size and shape control the final performance and properties of the minerals. Much has been published using different techniques to describe the aspect ratio of platy particles. This study describes a simple method to calculate aspect ratios for platy particles based on particle size data and specific surface area determined by nitrogen adsorption, exemplified with three different talc grades which vary in their amount of specific surface area and geological origin, as well as with one nano-sized synthetic Laponite (Laponite® RD) to illustrate the sensitivity to input parameters and their physical interpretation. The contrast between mass/volume and number probability distribution of particle size is discussed and illustrated.

Effects of beryllium metal particles on the viability and function of cultured rat alveolar macrophages

The physicochemical properties of particles influence their in vivo toxicity following deposition in the respiratory tract. To evaluate the relative contributions of mass and surface area to particle-induced toxicity, rat pulmonary alveolar macrophages (PAM) were exposed to four types of particles in vitro. We used three beryllium metal samples: relatively large (Be-II) and relatively small (Be-V) sized fractions of beryllium metal obtained from an aerosol cyclone, and a beryllium metal aerosol generated by laser vaporization of bulk beryllium metal in an argon atmosphere (Be-L). We also used glass beads (GB) as a negative control particle. End points examined included cell viability, determined by trypan blue dye exclusion, and changes in phagocytic ability, measured by counting the number of sheep red blood cells internalized by the PAM. Phagocytic ability was inhibited by exposure to beryllium particles at concentrations that did not cause appreciable cell death. Results describing effects based on the mass concentration of particles in culture medium were transformed by the amount of specific surface area of the particles to permit the expression of toxicity relative to the amount of particle surface per unit volume of culture medium. On a mass basis, the order of particle-related cytotoxicity was Be-L greater than Be-V greater than Be-II greater than GB, and for inhibition of phagocytosis, the order was Be-L approximately Be-V greater than Be-II greater than GB. When analyzed on a specific surface area basis, the cytotoxicity of the different materials became more similar in a fashion that was largely predicted by the amount of surface of the particles administered. However, because differences in specific surface area among the beryllium particle samples did not entirely predict cytotoxicity, we concluded that factors in addition to specific surface area influenced the expression of toxic effects in cultures of PAM exposed to beryllium metal.