Helium permeability of microspherical membranes based on mullitized cenospheres

Fomenko, Elena V.; Anshits, N. N.; Pankova, M. V.; Solovyov, Leonid A.; Верещагин, С. Н.; Anshits, A. G.; Фомин, В. М.

doi:10.1134/s0012501610120031

Cited by 12 publications

(6 citation statements)

References 7 publications

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“…In recent years, new functional materials have been developed based on a detailed characterization of narrow fractions of cenospheres with specific composition and structure. , Among these materials are high-selectivity microspherical membranes for diffusion separation of gases, − effective composite sorbents, , including those capable of operating in corrosive medium, , magnetically controlled encapsulated pH-sensitive spin probes for the examination of biological objects, supported catalyst systems, − and emulsion explosive sensitizers capable of replacing expensive hollow synthetic microspheres …”

Section: Introductionmentioning

confidence: 99%

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

et al. 2015

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The relationship between the chemical composition and shell structure of cenospheres with a low bulk density of 0.40−0.45 g/cm 3 and a high Al 2 O 3 content of 33−38 wt % has been systematically studied. It was established that the composition of the narrow fractions of cenospheres can be described by the general regression equation SiO 2 /Al 2 O 3 = 4.34 − 0.08[Al 2 O 3 ] with the correlation coefficient of r = −0.99. The phase composition includes the glass phase (57−73 wt %), mullite (25−40 wt %), and quartz (1.2−2.5 wt %). An increase in the Al 2 O 3 content leads to an increase in the size of particles and the porosity of their shells. In the obtained fractions of cenospheres, there are two types of globules: spherical globules with a singlering structure and foamy globules with a network structure. It is established that the composition of individual particles with a network structure localized in the range of the Al 2 O 3 content from 43 wt % to 51 wt % and can be described by the regression equation SiO 2 /Al 2 O 3 = 2.71 − 0.04[Al 2 O 3 ] with the correlation coefficient of r = −0.97. The framework of these particles permeated by mullite microcrystallites and coated with a nanoscale surface film. The structure-forming mineral precursor of these particles is kaolinite. The gross composition of the shell of individual globules with a single-ring structure localized in the range of the Al 2 O 3 content from 26 wt % to 42 wt % and can be described by the general regression equation SiO 2 /Al 2 O 3 = 4.71− 0.09[Al 2 O 3 ] with the correlation coefficient of r = −0.98. The outer and inner surfaces of the shell are covered by large and small in-plane localized mullite crystals hidden by the nanoscale film. The spherical shape and their crystalline framework are formed from the illite melt with inclusions of products of the thermal conversion of other mineral forms. ■ INTRODUCTIONIn the process of generating power from coal, large quantities of coal combustion products (CCPs) are produced. According to the various estimates, combustion of coal in the Russia alone generates ∼25 million tons of CCPs per year but utilization rate does not exceed 15%. 1 The complex composition of CCPs, including the fly ash, has proven to be a barrier to its bulk utilization in many fields. Extraction of concentrates of microspherical components with specific characteristics from fly ashes of variable composition provides wider opportunities for the multicomponent use of fly ashes produced from coal combustion. 2,3 The unique properties of cenospheres, namely, their low density, sphericity of particles, and high strength and nontoxicity, make them useful for a variety of fields of applications. Thus, concentrates of cenospheres are used as fillers of lightweight composite materials, such as concretes, 4,5 polymers and resins, 6−8 and metal alloys. 9,10 Also, they are been studied for the production of ceramic composite foams with different properties. 11,12 In recent years, new functional materials have been developed based on a d...

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Section: Introductionmentioning

confidence: 99%

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

et al. 2015

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“…21 The stabilization of composition and, correspondingly, properties of cenospheres, owing to the differences in physical characteristics of individual globules (size, density, and magnetic properties), makes it possible to use them instead of expensive synthetic microspheres in the fabrication of new functional materials. In particular, narrow fractions of cenospheres have been used in the fabrication of microspherical sorbents with zeolite/mullite composite shells, 22 sensitizers of commercial emulsion explosives, 23 multifunctional porous materials for liquid radioactive waste treatment, 24 sorbents, 25 pH-sensitive spin probes of molecular systems, 26 microspherical membranes for selective separation of helium, 27,28 metal-matrix syntactic foams, 29 and composite sorbents with a deposited magnetic component and a functionalized surface for extraction of phenolic compounds from aqueous media. 30 In each case where cenospheres are used for the production of functional materials with predictable properties, it is necessary to know the chemical and phase compositions of their narrow fractions.…”

Section: ■ Introductionmentioning

confidence: 99%

Composition and Morphology of Fly Ash Cenospheres Produced from the Combustion of Kuznetsk Coal

et al. 2013

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The chemical and phase composition, morphology, and shell structure of narrow fractions of nonmagnetic and magnetic low-density nonperforated cenospheres separated from fly ash concentrates produced via the pulverized combustion of coal from the Kuznetsk Basin (Russia) have been studied. Narrow fractions of nonmagnetic cenospheres contain 2.6–3.5 wt % Fe2O3 and include globules with a uniform smooth or relief surface and shells with different degrees of porosity. For nonmagnetic cenospheres, the aluminum concentration increase leads to an increase in the mullite phase content and a decrease in the average sphere diameter, glass-crystalline shell thickness and porosity, and the crystalline quartz content. The quartz phase comprises two modifications with different lattice parameters. The narrow fractions of magnetic cenospheres contain 3–21 wt % Fe2O3 and include globules with thick porous shells covered by heterogeneous regions of ferrospinel on their outer surface. In magnetic cenospheres, an increase in the iron concentration leads to an increase in the ferrospinel phase content and crystallite size, accompanied by a decrease in the degree of substitution of magnesium and aluminum for iron.

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“…High-quality separation of ash into fractions with a certain size and composition and with predictable properties enables conversion of large-scale waste of thermal power plants into valuable mineral raw materials of technogenic origin. In recent years, production of functional materials based on individual fly ash components, such as adsorbents, catalysts, carriers, ceramic materials, and zeolites, has attracted great interest of researchers. ,,,− For example, narrow fractions of 50–250 μm hollow aluminosilicate microspheres (cenospheres) separated from fly ash − were used to fabricate hydrogen storage containers and highly selective membranes for diffusion-based extraction of helium, − emulsion explosive sensitizers, encapsulated pH-sensitive spin probes for studying biological objects, and composite sorbents for extraction of radionuclides from liquid radioactive waste. , …”

Section: Introductionmentioning

confidence: 99%

Separation of Nonmagnetic Fine Narrow Fractions of PM₁₀ from Coal Fly Ash and Their Characteristics and Mineral Precursors

et al. 2019

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Nonmagnetic fine narrow fractions of particles with mean diameters of 2, 3, 6, and 10 μm were for the first time separated from fly ash produced by pulverized combustion of Ekibastuz coal using aerodynamic classification with subsequent magnetic separation. These fractions were characterized by the size distribution, bulk density, and chemical and phase compositions. The particle size distributions correspond to d 50 values of 1.9, 2.3, 5.1, and 9.2 μm. As the fraction particle size increases, the bulk density was found to rise gradually from 0.90 to 1.07 g/cm3. The main components of the chemical composition were SiO2 (65–70 wt %) and Al2O3 (23–28 wt %). The phase composition was represented by the glass phase (64–69 wt %), mullite (17–21 wt %), and quartz (10–18 wt %). The main morphological particle types were microspheres with a nonporous smooth surface and microspheres with a porous shell. With an increase in the fraction particle size, the percentage of microspheres with a porous shell increases. The largest fraction contains particles with a network structure. Single-particle scanning electron microscopy–energy dispersive X-ray spectroscopy analysis of nonporous microspheres with a diameter of 1–2 μm, approximate in composition to the internal coal minerals, indicated that, depending on the content of SiO2, Al2O3, and FeO, they form several groups differing in mineral precursors. Thus, for microspheres of group 1 (SiO2 + Al2O3 > 95 wt %), the mineral precursors are NH4-illite and montmorillonite; group 2 (SiO2 + Al2O3 = 90–95, FeO ≤ 4 wt %)minerals of the isomorphic montmorillonite-illite series, including phases with a low level of iron cation substitution; group 3 (SiO2 + Al2O3 = 90–95, 4 < FeO ≤ 6 wt %) and group 4 (SiO2 + Al2O3 < 90, 3 < FeO ≤ 9 wt %)minerals of the illite-montmorillonite series, with a high level of iron cation substitution and with Fe3+ in interlayer sites.

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Helium permeability of microspherical membranes based on mullitized cenospheres

Cited by 12 publications

References 7 publications

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

Composition and Morphology of Fly Ash Cenospheres Produced from the Combustion of Kuznetsk Coal

Separation of Nonmagnetic Fine Narrow Fractions of PM₁₀ from Coal Fly Ash and Their Characteristics and Mineral Precursors

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Helium permeability of microspherical membranes based on mullitized cenospheres

Cited by 12 publications

References 7 publications

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

Characterization of Fly Ash Cenospheres Produced from the Combustion of Ekibastuz Coal

Composition and Morphology of Fly Ash Cenospheres Produced from the Combustion of Kuznetsk Coal

Separation of Nonmagnetic Fine Narrow Fractions of PM10 from Coal Fly Ash and Their Characteristics and Mineral Precursors

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Separation of Nonmagnetic Fine Narrow Fractions of PM₁₀ from Coal Fly Ash and Their Characteristics and Mineral Precursors