scholarly journals Effect of Carbon Deposits on the Structure of Hybrid C/TiO2/SiO2 Adsorbents

2001 ◽  
Vol 19 (5) ◽  
pp. 385-395 ◽  
Author(s):  
R. Leboda ◽  
V.M. Gun'ko ◽  
M. Marciniak ◽  
W. Grzegorczyk ◽  
J. Skubiszewska-Zięba
Keyword(s):  
Silica Gel ◽  
Fumed Silica ◽  
Structural Characteristics ◽  
Nitrogen Adsorption ◽  
Structural Features ◽  
Carbon Phase ◽  
Pore Size Distributions ◽  
Improved Technique ◽  
Adsorption Desorption ◽  
Desorption Method

The structural characteristics of pyrocarbon/X (X = fumed silica, mesoporous silica gel, fumed titania/silica, CVD-TiO2/fumed silica, CVD-TiO2/silica gel) prepared using several precursors [CH2Cl2, cyclohexene and TiO(AcAc)2, where Ac = acetylacetonate] were studied using the nitrogen adsorption/desorption method and an improved technique to allow the calculation of pore size distributions applying regularization procedures. Various pore models were used for the carbon phase. The pyrocarbon structure and distribution on the TiO2/SiO2 supports depends primarily on the structural features of the titania phase which exhibits catalytic activity in the pyrolysis of organic materials. The formation of relatively large concentrations of pyrocarbon typically reduces the porosity and specific surface area of the hybrid adsorbents produced.

scholarly journals The Morphology and Conductive Properties of Composite Material SiO2 – C

2015 ◽  
Vol 16 (4) ◽  
pp. 700-705
Author(s):  
I.F. Myronyuk ◽  
V.I. Mandzyuk ◽  
V.M. Sachko ◽  
Yu.O. Kyluk
Keyword(s):  
Composite Material ◽  
Fumed Silica ◽  
Silica Surface ◽  
Weight Ratio ◽  
Nitrogen Adsorption ◽  
Carbon Phase ◽  
Fumed Silica Nanoparticles ◽  
Structure Morphology ◽  
Open Porous Structure ◽  
Conductive Properties

The article explores the structure, morphology and conductive properties of composite material SiO2 – C using XRD, SAXS, low-temperature nitrogen adsorption, and impedance spectroscopy methods. It is set that SiO2 – C composite obtained by thermolytic decomposition of D-lactose, previously chemisorbed on fumed silica nanoparticles surface, has an open porous structure, in which mesopores of 6-12 nm in size are dominate. At weight ratio SiO2/C = 5/1 nanocrystallites of carbon phase in form of lamellar sheets of 0,4 × 0,4 × 5,0 nm3 in size contact with entire silica surface that results in composite material conductivity is 49 Оhm-1·m-1.

Low Surface Coverage Interactions of Sulfur Dioxide on Selected Transition Metal Catalysts from 273 to 423 °K

1971 ◽  
Vol 49 (17) ◽  
pp. 2832-2839 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Transition Metal ◽  
Silica Gel ◽  
Surface Coverage ◽  
Nitrogen Adsorption ◽  
Metal Catalysts ◽  
Transition Metal Catalysts ◽  
Hydrogen Bond Formation ◽  
Support Medium ◽  
Adsorption Desorption

Calorimetric beats of adsorption for sulfur dioxide at low surface coverages from 0.004 to 0.600 μmol m−2 on a number of supported transition metal catalysts have been measured between 273 and 423 °K mainly by an adiabatic technique. The catalysts included Fe2O3, Mn2O3, V2O5, MnSO4, and "NiS" ail supported on silica gel.Sulfur dioxide adsorption/desorption isotherms, nitrogen adsorption data, and chemical and infrared analyses were also determined to provide further ancillary information.Heats of adsorption at 423 °K for adsorbed amounts of 0.004 μmol m−2 varied with the adsorbent from nearly 39.0 for Mn2O3 on silica gel to 23.0 kcal mol−1 for the silica gel support medium. With increase in surface coverage to 0.600 μmol m−2 the heat values begin to steady at 6 to 7, 7 to 8, and 8 to 9 kcal mol−1 at 423, 373, and 323 °K, respectively, and less discrimination is observed among the various materials. Preadsorption of small amounts of sulfur dioxide on the supported oxides followed by oxygen admission caused sharp initial falls of as much as 7 to 8 kcal mol−1 in the heat values whereas preadsorption of oxygen followed by sulfur dioxide gave only slight heat increases of around 1 kcal mol−1.It is proposed that sulfur dioxide is chemisorbed on all surfaces with the strongest interactions occurring at the lowest coverages. Sulfates are formed on the oxides as confirmed by chemical analysis, and it is postulated that multiple hydrogen bond formation occurs on silica gel through the interaction of sulfur dioxide oxygen atoms with surface hydroxy groups.

scholarly journals Surfactant-Free Solvothermal Method for Synthesis of Mesoporous Nanocrystalline TiO2Microspheres with Tailored Pore Size

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Yajing Zhang ◽  
Sujuan Zhang ◽  
Kangjun Wang ◽  
Fu Ding ◽  
Jing Wu
Keyword(s):  
Pore Size ◽  
Anatase Phase ◽  
Nitrogen Adsorption ◽  
Ethanol Solution ◽  
Tetrabutyl Titanate ◽  
Size Distributions ◽  
Pore Size Distributions ◽  
Structure Morphology ◽  
Mesoporous Microspheres ◽  
Adsorption Desorption

TiO2mesoporous microspheres self-assembled from nanoparticles were synthesized by a surfactant-free solvothermal route. The TiO2precursors were fabricated by tetrabutyl titanate, glacial acetic acid, and urea in the ethanol solution at 140°C for 20 h, and TiO2mesoporous microspheres were obtained by a postcalcination at temperatures of 450°C for promoting TiO2crystallization and the removal of residual organics. The phase structure, morphology, and pore nature were characterized by XRD, SEM, and nitrogen adsorption-desorption measurements. The as-prepared TiO2microspheres are in anatase phase, with 2-3 μm in diameter, and narrow pore distribution range is 3-4 nm. The adjustments of the synthetic parameters lead to the formation of the mesoporous TiO2microspheres with tuned pore size distributions and morphology.

scholarly journals Ordered Mesoporous Silica Materials for Protein Adsorption

2010 ◽  
Vol 636-637 ◽  
pp. 54-59 ◽  
Author(s):  
F. Sezões ◽  
Manuela M.L. Ribeiro Carrott ◽  
Paulo A.M. Mourão ◽  
P.A. Russo ◽  
Peter J.M. Carrott
Keyword(s):  
Mesoporous Silica ◽  
Protein Adsorption ◽  
Structural Characteristics ◽  
Structural Features ◽  
Ordered Mesoporous Silica ◽  
Ordered Mesoporous ◽  
Pore Size Distributions ◽  
Silica Materials ◽  
Mesoporous Silica Materials ◽  
Mcm 41

Lysozyme and BSA were used, as model proteins of considerably different dimensions, in order to evaluate the influence of the distinct pore structural characteristics of three types of ordered mesoporous silica materials (MCF, SBA-15 and MCM-41) on protein adsorption. Characterisation by X ray diffraction and nitrogen adsorption at 77K revealed the typical pore structural features of each type of material. The maximum of the pore size distributions indicated that the width of the windows of MCF (2) (mesitylene/P123 of 2) was larger than the pore diameter of the unidirectional tubular pores of SBA-15. All the materials presented similar small external surface areas but high pore volumes, with that of MCF (2) being the highest. The adsorption of lysozyme at pH=8 increased in the order MCM-41<< SBA-15< MCF (2), and the uptakes were well above those of BSA at pH=5. Although BSA is not completely excluded from the mesopores of SBA-15 and MCF (2), as happens with MCM-41, the adsorption occurs to a very limited extent. The overall behaviour of these SBA-15 and MCF (2) samples was not significantly different and both revealed potential for the separation of these proteins.

scholarly journals Influence of yttrium and niobium oxides modifiers on physicochemical and photocatalytic properties of titanium (IV) oxide

2021 ◽  
Vol 4 (6(112)) ◽  
pp. 67-74
Author(s):  
Svitlana Kyrii ◽  
Tetiana Dontsova ◽  
Iryna Kosogina ◽  
Valeriia Podopryhor ◽  
Alla Serhiienko
Keyword(s):  
Structural Characteristics ◽  
Surface Acidity ◽  
Nitrogen Adsorption ◽  
Photocatalytic Properties ◽  
Commercial Sample ◽  
Niobium Oxides ◽  
Oxide Powders ◽  
Adsorption Desorption ◽  
Modification Of Titanium

The photocatalytic and physicochemical properties of titanium (IV) oxide modified by yttrium and niobium oxides were studied. It is shown that modification is a powerful way to increase the efficiency of catalysts' photocatalytic properties and improve the photocatalytic process as a whole. Commercial and laboratory-synthesized titanium (IV) oxides were used as catalysts for modification. Modification of titanium (IV) oxide powders in an amount of 1 wt. % by appropriate modifiers was performed by the hydrothermal method, after which they were characterized by diffraction and X-ray fluorescence methods. The structural characteristics of modified and non-modified titanium (IV) oxide samples by the method of low-temperature nitrogen adsorption-desorption have been studied. A slight increase in the specific surface area was found: from 61 m2/g to 70 m2/g for the commercial sample and from 172 m2/g to 180 m2/g for the synthesized one in this work. Similar dependencies are observed when studying the optical properties by the spectrophotometric method. Determination of surface properties (surface acidity) of modified and non-modified photocatalysts based on TiO2 showed different effects of modifiers on TiO2 acidity: in the modification by yttrium oxide, the acidity decreases, and in the case of niobium oxide – increases. Studies of photocatalytic and sorption activities with respect to dyes of different nature are not the same – the photocatalytic activity after modification increases, the sorption capacity with the cationic dye decreases, anionic – increases. Additional studies on dye destruction are in full accordance with photocatalytic and sorption experiments.

Novel Route for Incorporation of Palladium Nanoparticles into Mesostructured Silicas Sba 15 and Sba-16

2013 ◽  
Vol 22 (3) ◽  
pp. 096369351302200
Author(s):  
N. Ivashchenko ◽  
V. Tertykh ◽  
J. Skubiszewska-Zięba ◽  
R. Leboda ◽  
S. Khainakov ◽  
...  
Keyword(s):  
Palladium Nanoparticles ◽  
Nitrogen Adsorption ◽  
Pd Nanoparticles ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Adsorption Desorption ◽  
Desorption Method ◽  
Material Study

Palladium nanoparticles with controlled size were synthesized within the pores of the mesoporous SBA-15 and SBA-16 silicas with grafted silicon hydride groups. Nitrogen adsorption-desorption method, X-ray diffraction and transmission electron microscopy (TEM) were used for characterization of palladium-containing composites. Results of material study clearly revealed that Pd nanoparticles prepared by this method were located inside the porous channels and were quite uniform in size (mostly 5–6 nm). The influence of metal content on the particles size and porous structure of supports was investigated.

scholarly journals Nanostructured Polymethylsiloxane/Fumed Silica Blends

Materials ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 2409 ◽  
Author(s):  
Iryna Protsak ◽  
Volodymyr M. Gun’ko ◽  
Volodymyr V. Turov ◽  
Tetyana V. Krupska ◽  
Eugeniy M. Pakhlov ◽  
...  
Keyword(s):  
Mechanical Loading ◽  
Fumed Silica ◽  
Silica Surface ◽  
Nitrogen Adsorption ◽  
Drug Carriers ◽  
Point Of View ◽  
Sem Images ◽  
Textural Characteristics ◽  
Adsorption Desorption ◽  
Cp Mas Nmr

Polymethylsiloxane (PMS) and fumed silica, alone and in a blended form (1:1 w/w), differently pretreated, hydrated, and treated again, were studied using TEM and SEM, nitrogen adsorption–desorption, 1H MAS and 29Si CP/MAS NMR spectroscopy, infrared spectroscopy, and methods of quantum chemistry. Analysis of the effects of adding water (0–0.5 g of water per gram of solids) to the blends while they are undergoing different mechanical treatment (stirring with weak (~1–2 kg/cm2) and strong (~20 kg/cm2) loading) show that both dry and wetted PMS (as a soft material) can be grafted onto a silica surface, even with weak mechanical loading, and enhanced mechanical loading leads to enhanced homogenization of the blends. The main evidence of this effect is strong nonadditive changes in the textural characteristics, which are 2–3 times smaller than additive those expected. All PMS/nanosilica blends, demonstrating a good distribution of nanosilica nanoparticles and their small aggregates in the polymer matrix (according to TEM and SEM images), are rather meso/microporous, with the main pore-size distribution peaks at R > 10 nm in radius and average <RV> values of 18–25 nm. The contributions of nanopores (R < 1 nm), mesopores (1 nm < R < 25 nm), and macropores (25 nm < R < 100 nm), which are of importance for studied medical sorbents and drug carriers, depend strongly on the types of the materials and treatments, as well the amounts of water added. The developed technique (based on small additions of water and controlled mechanical loading) allows one to significantly change the morphological and textural characteristics of fumed silica (hydrocompaction), PMS (drying–wetting–drying), and PMS/A-300 blends (wetting–drying under mechanical loading), which is of importance from a practical point of view.

scholarly journals Influence of the Synthesis Method on the Structural Characteristics of Novel Hybrid Adsorbents Based on Bentonite

2019 ◽  
Vol 3 (1) ◽  
pp. 18 ◽  
Author(s):  
Dariusz Sternik ◽  
Mariia Galaburda ◽  
Viktor Bogatyrov ◽  
Volodymyr Gun’ko
Keyword(s):  
Structural Characteristics ◽  
Synthesis Method ◽  
Nitrogen Adsorption ◽  
Inert Atmosphere ◽  
Scanning Calorimetry ◽  
Resorcinol Formaldehyde ◽  
X Ray Scattering ◽  
Adsorption Desorption ◽  
Tga And Dsc ◽  
Thermal Stability Of

New hybrid composite materials were prepared by polymerization of resorcinol–formaldehyde resins in the presence of bentonite with various contents of polymer and water, and then exposed to pyrolysis in an inert atmosphere at 800 °C. The influence of the filler and synthesis method on the morphological, textural and structural characteristics has been described. The materials were characterized using low temperature nitrogen adsorption–desorption, small angle X-ray scattering, scanning electron microscopy, Raman spectroscopy, differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). The maximal values of the specific surface area of organo-bentonite and carbonized samples were 254 and 200 m2/g, respectively, which is much larger than that of the initial bentonite. The TGA and DSC experiments showed changes in the thermal stability of samples depending on their composition. The obtained data could provide a better understanding of the principles of preparing hybrid bentonite-containing composites that may provide an additional incentive to develop advanced technologies.

scholarly journals Structural properties and adsorption of uranyl ions on the nanocomposite hydroxyapatite/white clay

2021 ◽  
Author(s):  
E. Broda ◽  
A. Gładysz-Płaska ◽  
E. Skwarek ◽  
V. V. Payentko
Keyword(s):  
Zeta Potential ◽  
Surface Charge Density ◽  
Potential Surface ◽  
Nitrogen Adsorption ◽  
Uranyl Ions ◽  
Uranium Removal ◽  
Nanocrystalline Composites ◽  
Adsorption Desorption ◽  
Desorption Method ◽  
White Clay

AbstractUranium is more and more extensively applied as a source of energy and can be potentially used for nuclear weapon production. Owing to that fact, the problem of uranium expansion in the environment is the object of research and draw attention many scientists. One of the most effective methods of uranium removal from the wastewater (where uranium is present in a low concentration and occurs mainly in the form of uranyl ion, UO22+) is the adsorbent usage. It is important to discover an adsorbent which will be effective, widely available and cheap. The paper discusses properties and the ability of U (VI) adsorption on a clay and nanocomposite clay/Hap (hydroxyapatite) obtained by wet method. The adsorbents were characterized by the mentioned below tests: XRD, XRF, the porosity (nitrogen adsorption–desorption method), zeta potential, surface charge density and sorption of U (VI). It was shown that nanocrystalline composites Hap/white clay can be appropriate adsorbent for removal of uranyl ions. The adsorption depends on the temperature and pH of the solution.

scholarly journals Insight into Relationship between Thermal Dissolution of Low-Rank Coals and Their Subsequent Oxidative Depolymerization

Energies ◽  
2021 ◽  
Vol 15 (1) ◽  
pp. 32
Author(s):  
Yugao Wang ◽  
Xiaochen Liu ◽  
Zhilei Wang ◽  
Chuan Dong ◽  
Jun Shen ◽  
...  
Keyword(s):  
Nitrogen Adsorption ◽  
Structural Features ◽  
Space Structure ◽  
Oxidation Products ◽  
Low Rank ◽  
Thermal Dissolution ◽  
Physico Chemical ◽  
Adsorption Desorption ◽  
The Relationship ◽  
Low Rank Coals

Oxidative depolymerization of low-rank coals is promising for obtaining benzene carboxylic acids (BCAs). However, it is hindered by the low yield of BCAs along with a large number of alphatic acids. Thermal dissolution could modify the physico-chemical structural features of low-rank coals, which is expected to improve the oxidation of LRCs. In this paper, lignite and subbituminous coal were firstly subjected to thermal dissolution with cyclohexane at 250 °C for 2 h. Then, the raw coal and the corresponding thermal insoluble portion (TIP) were oxidized by NaOCl under the same conditions. The residual yields of TIPs oxidation were both lower than those of raw coals oxidation, indicating that TIPs were more easily oxidized than the raw coals. The yield of BCAs obtained by TIPs oxidation was above 19% higher than that from the oxidation of raw coals. Meanwhile, the selectivity of BCAs was improved in the resulting oxidation products from TIPs compared with that from the raw coals. The relationship between BCAs generation and thermal dissolution of low rank coals was investigated by ultimate analysis, Fourier transform infrared spectroscopy, and nitrogen adsorption-desorption analysis. The results suggested that thermal dissolution could enrich aromatic portion in the remaining TIPs, resulting in an increasing of the yield and selectivity of BCAs. Simultaneously, thermal dissolution raised the specific surface area and expanded the looser space structure of TIPS, which were beneficial for the sufficient collision between aromatic structures and oxidant, facilitating the oxidative depolymerization of TIPs. This investigation would provide a novel route for promoting BCAs production by mild oxidative depolymerization of low-rank coals.

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