Adiabatic Calorimetric Studies of the Adsorption of Sulfur Dioxide at 423 °K on Heat-treated Magnesias Characterized by Electron Microscopy

1972 ◽  
Vol 50 (17) ◽  
pp. 2817-2822 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Nitrogen Adsorption ◽  
High Energy ◽  
Structural Features ◽  
Average Particle ◽  
Cubic Form ◽  
Transmission Electron ◽  
Heat Treated ◽  
Calorimetric Studies ◽  
Adsorption Desorption

Calorimetric heats of adsorption of sulfur dioxide at surface coverages from 0.2 to 7.7 μmol m−2 have been measured on a series of magnesias heat-treated at 600, 700, and 800 °C. Structural features of the adsorbents have been characterized by analysis of nitrogen adsorption–desorption isotherms and by transmission electron microscopy.Heats of adsorption at 423 °K for adsorbed amounts of 0.3 μmol m−2 were respectively, 86.0, 87.0, and 77.0 kcal mol−1 for the 600, 700, and 800 °C samples. The values for the 600 and 700 °C samples fell rapidly above a coverage of 2.0 μmol m−2 to around 44.0 kcal mol−1 at 5.0 to 7.0 μmol m−2, while the values for the 800 °C sample decreased continuously to 39.0 kcal mol−1 at the same coverage.Crystallite shapes tended increasingly towards the cubic form as the temperature of heat-treatment was increased and average particle sizes were 80, 240, and 320 Å for the 600, 700, and 800 °C samples, respectively.It is proposed that the very high heats obtained on all the samples are due to interactions with high-energy defect centers in the oxide and with the formation of magnesium sulfite initially, and magnesium sulfate towards monolayer completion.

Surface Studies of Heat-treated γ-Aluminas in the Adsorption of Sulfur Dioxide below Monolayer Coverage

1972 ◽  
Vol 50 (16) ◽  
pp. 2537-2543 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Cross Sections ◽  
Nitrogen Adsorption ◽  
High Energy ◽  
Spherical Particles ◽  
Defect Centers ◽  
Heat Treated ◽  
Adsorption Desorption ◽  
Very High ◽  
Monolayer Coverage

Calorimetric heats of adsorption of sulfur dioxide at surface coverages from 0.1 to 3.5 µmol m−2 have been measured on a series of γ-aluminas heat-treated at 500, 700, and 900 °C. Essential features of the structures of the adsorbents have been characterized by analysis of nitrogen adsorption/desorption isotherms and by both direct and indirect electron microscopy.Heats of adsorption of 423 °K for adsorbed amounts of 0.1 µmol m−2 were 48.0, 59.0, and 85.0 kcal mol−1 for the 500, 700 and 900 °C samples, respectively. The values for the 500 and 700 °C samples fell rapidly with increasing coverage to around 19.0 kcal mol−1 at 3.2 to 3.3 µmol m−2, while the values for the 900 °C sample decreased slowly to 15.0 kcal mol−1 at the same coverage.The pores had circular cross sections and mean diameters of 25, 35, and 40 Å were observed for the 500, 700, and 900 °C samples, respectively. Examination of carbon/platinum replicas of the surface showed the presence of agglomerates of spherical particles approximately 400 Å in diameter.It is proposed that the high initial heats on the 500 and 700 °C samples are due to the formation of a sulfate-like species on the surface and at higher coverage extensive hydrogen bonding is present. The very high heats obtained on the 900 °C sample are believed to be due to interactions with high-energy defect centers in the oxide which were created by heat treatment.

scholarly journals Structural, Mineral and Elemental Composition Features of Iron-Rich Saponite Clay from Tashkiv Deposit (Ukraine)

2019 ◽  
Vol 3 (1) ◽  
pp. 10 ◽  
Author(s):  
Halyna Sokol ◽  
Myroslav Sprynskyy ◽  
Alla Ganzyuk ◽  
Victoria Raks ◽  
Bogusław Buszewski
Keyword(s):  
Electron Microscopy ◽  
Mineral Resources ◽  
Total Pore Volume ◽  
Nitrogen Adsorption ◽  
Structural Features ◽  
Narrow Slit ◽  
Porous System ◽  
Transmission Electron ◽  
A Charge ◽  
Adsorption Desorption

Low-temperature nitrogen adsorption–desorption isotherms, scanning electron microscopy, transmission electron microscopy, X-ray diffraction, as well as infrared spectroscopy were used to characterize structural features of raw and acid-treated saponite from Tashkiv deposit of Ukraine. It was determined that raw saponite is predominantly composed of trioctahedral saponite with an admixture of dioctahedral nontronite and associated minerals such as quartz, hematite, and anatase. Raw saponite clay was characterized by a high content of iron (19.3%) and titanium (1.1%). Iron is present in the form of hematite particles, isomorphic replacements in octahedral and tetrahedral sheets of a clay structure, or as a charge-balancing cation in the interlayer space. Titanium is homogeneously dispersed as submicrometer anatase particles. The porous structure of both saponite forms consists of micro-meso porous system with narrow slit mesopores dominating. As a consequence of the acid treatment, the specific surface area increased from 47 to 189 m2 g−1, the total pore volume from 0.134 to 0.201 cm3 g−1, and the volume of the micropores increased sevenfold. Using the data of our research allowed us to utilize these mineral resources wisely and to process saponite more efficiently.

The Effects of Milling Methods on Doped LaCrO3 Nanopowder Prepared by Glycine Nitrate Process on Particle Size and Phase Transformation

2012 ◽  
Vol 428 ◽  
pp. 127-132
Author(s):  
Akbar Heidarpour ◽  
Ali Saidi ◽  
Mohamad Hasan Abbasi
Keyword(s):  
Particle Size ◽  
Phase Transformation ◽  
Nitrogen Adsorption ◽  
High Energy ◽  
Lanthanum Chromite ◽  
Second Phase ◽  
Transmission Electron ◽  
Particle Size Analyzer ◽  
Adsorption Desorption ◽  
Glycine Nitrate Process

In this study the effects of milling methods on particle size and phase transformation of strontium and nickel doped lanthanum chromite as an interconnect material for solid oxide fuel cells (SOFC) were investigated. Two compositions of La0.9Sr0.1Cr0.9Ni0.1O3 (LS10N10) and La0.7Sr0.3Cr0.9Ni0.1O3 (LS30N10) were synthesized by glycine nitrate process (GNP). The samples were characterized by means of X-ray diffraction, nitrogen adsorption–desorption, scanning and transmission electron microscope and laser particle size analyzer. Two different milling methods were used, namely, high-energy milling (HEM) and ball milling (BM) and the effects of these milling methods of as-synthesis powders on the particle size distribution, agglomeration behavior and phase transformation were also investigated. The results showed that BM caused reduction of particle size to submicron size with D50 value of 125 nm while HEM resulted in agglomeration. The obtained nanopowders, according to XRD results were single phase with perovskite type crystal structure and only in high content of Sr some SrCrO4 was detected. HEM caused the dissolution of the second phase in LS30N10.

The Effect of Heat Treatment of Silica Gels on the Calorimetric Heats of Adsorption of Sulfur Dioxide up to One-twentieth Monolayer Coverage at 423 °K

1972 ◽  
Vol 50 (8) ◽  
pp. 1241-1245 ◽  
Author(s):  
R. W. Glass ◽  
R. A. Ross
Keyword(s):  
Sulfur Dioxide ◽  
Nitrogen Adsorption ◽  
Silica Gels ◽  
Distribution Data ◽  
Heats Of Adsorption ◽  
Heat Treated ◽  
Adsorbed Complex ◽  
Adsorption Desorption ◽  
Limiting Values ◽  
Dual Site

Calorimetric heats of adsorption of sulfur dioxide have been determined at 423°K for a series of silica gels heat-treated at 240, 550, 700, 800, and 900 °C. At the lowest surface coverage of 0.01 μmol m−2, heats of 25 to 30 kcal mol−1 were observed. These values dropped rapidly with increasing coverage and approached "limiting" values of 6 to 7 and 12 kcal mol−1 for dehydroxylated and hydroxylated surfaces, respectively. To explain the results at lowest coverages an adsorbed complex involving multiple hydrogen bonds is proposed while at higher coverages it is suggested that single and dual site adsorbed species predominate for the dehydroxylated and hydroxylated surfaces, respectively. Sulfur dioxide adsorption isotherms on all gels at 423 °K obeyed the Langmuir equation.Adsorbents were characterized by nitrogen adsorption–desorption isotherms at 77 °K and pore size distribution data were calculated from the desorption branch.

Texture Evaluation of Sol-Gel Derived Mesoporous Bioactive Glass

2013 ◽  
Vol 284-287 ◽  
pp. 230-234
Author(s):  
Yu Jen Chou ◽  
Chi Jen Shih ◽  
Shao Ju Shih
Keyword(s):  
Surface Area ◽  
Calcination Temperature ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Nitrogen Adsorption ◽  
Bioactive Glasses ◽  
Transmission Electron ◽  
Sol Gel Process ◽  
Adsorption Desorption

Recent years mesoporous bioactive glasses (MBGs) have become important biomaterials because of their high surface area and the superior bioactivity. Various studies have reported that when MBGs implanted in a human body, hydroxyl apatite layers, constituting the main inorganic components of human bones, will form on the MBG surfaces to increase the bioactivity. Therefore, MBGs have been widely applied in the fields of tissue regeneration and drug delivery. The sol-gel process has replaced the conventional glasses process for MBG synthesis because of the advantages of low contamination, chemical flexibility and lower calcination temperature. In the sol-gel process, several types of surfactants were mixed with MBG precursor solutions to generate micelle structures. Afterwards, these micelles decompose to form porous structures after calcination. Although calcination is significant for contamination, crystalline and surface area in MBG, to the best of the authors’ knowledge, only few systematic studies related to calcination were reported. This study correlated the calcination parameters and the microstructure of MBGs. Microstructure evaluation was characterized by transmission electron microscopy and nitrogen adsorption/desorption. The experimental results show that the surface area and the pore size of MBGs decreased with the increasing of the calcination temperature, and decreased dramatically at 800°C due to the formation of crystalline phases.

Positron Annihilation Study of Porous ZnO Synthesized with Soft Template

2017 ◽  
Vol 373 ◽  
pp. 299-302
Author(s):  
Bo Zhou ◽  
Chong Yang Li ◽  
Ning Qi ◽  
Zhi Quan Chen
Keyword(s):  
Pore Size ◽  
Positron Lifetime ◽  
Nitrogen Adsorption ◽  
Soft Template ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Long Lifetime ◽  
Positron Annihilation Study ◽  
Adsorption Desorption

Porous ZnO were synthesized with soft template method using zinc acetate Zn (CH3COO)2·2H2O as precursor and block copolymer F127 as the surfactant. Nitrogen adsorption-desorption measurements indicate that the ZnO sample contains large pores with mean diameter of about 30 nm. However, both small-angle X-ray diffraction and transmission electron microscope measurements indicate that the pore ordering is missing. Positron lifetime measurements reveal two long lifetime components in the porous ZnO. The longest lifetime τ4 (75 ns) corresponds to ortho-positronium (o-Ps) annihilation in large pores. The pore size estimated from τ4 is about 10.6 nm. This is much smaller than that estimated from Nitrogen adsorption-desorption measurements. In addition, the intensity I4 is only about 2.2%. This is probably due to the chemical quenching and/or inhibition of positronium formation induced by ZnO, which reduces o-Ps lifetime and intensity, and leads to under estimation of the pore size.

Catalytic Activity of Argentum-loaded MCM-41 for Ozonation of p- Chlorobenzoic Acid (p-CBA) in Aqueous Solution

2015 ◽  
Vol 18 (1) ◽  
Author(s):  
Zhaoqi Pan ◽  
Junyu Zeng ◽  
Bingyan Lan ◽  
Laisheng Li
Keyword(s):  
Aqueous Solution ◽  
Nitrogen Adsorption ◽  
Hexagonal Structure ◽  
Bet Surface Area ◽  
X Ray Diffraction ◽  
Chlorobenzoic Acid ◽  
Transmission Electron ◽  
Initial Ph ◽  
Adsorption Desorption ◽  
Mcm 41

AbstractArgentum-loaded MCM-41 (Ag/MCM-41) was synthesized successfully by a hydrothermal method and used as a catalyst for the ozonation of p-chlorobenzoic acid (p-CBA) in aqueous solution. Ag/MCM-41 was characterized by low angle X-ray diffraction (XRD), nitrogen adsorption-desorption and transmission electron microscopy (TEM). Characterizations suggest that the prepared samples retained a highly regulated mesopores of hexagonal structure and a high BET surface area. The influences of argentum content, initial pH, reaction temperature on the catalytic ozonation were also evaluated. Ag/MCM-41/O

Synthesis and Characterization of Mesoporous Molecular Sieve Al-MCM-41 Using Kaolin as Raw Material

2013 ◽  
Vol 779-780 ◽  
pp. 201-204
Author(s):  
Miao Li ◽  
Hong Wang ◽  
Xian Qing Li ◽  
Jin Rong Liu
Keyword(s):  
Molecular Sieve ◽  
Nitrogen Adsorption ◽  
Mesoporous Molecular Sieve ◽  
Raw Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Adsorption Desorption ◽  
Calcined Kaolin ◽  
Mcm 41

Ordered hexagonally mesoporous molecular sieve Al-MCM-41 with Si/Al (atom) ratio=9 was prepared by hydrothermal synthesis using raw kaolin. X-ray diffraction (XRD), Nitrogen adsorption desorption, Transmission Electron Microscope (TEM) and Energy Dispersive X-ray Detector (EDX) were employed to characterise raw kaolin, calcined kaolin, as-synthesized and calcined Al-MCM-41. The results indicated that characteristic reflections of raw kaolin disappeared after calcination, both of as-synthesized and calcined Al-MCM-41 exhibited well ordered hexagonally mesoporous molecular sieve structure.

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 Synthesis and Properties of Magnetic Carbon Nanocages Particles for Dye Removal

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Hengfei Qin ◽  
Yongkui Huang ◽  
Siyu Liu ◽  
Yao Fang ◽  
Xi Li ◽  
...  
Keyword(s):  
Raman Spectrum ◽  
Textile Wastewater ◽  
Nitrogen Adsorption ◽  
Cage Structure ◽  
X Ray ◽  
Transmission Electron ◽  
Magnetic Carbon ◽  
Hierarchical Pore ◽  
Adsorption Desorption ◽  
High Degree

Magnetic carbon nanocages (MCNCs) with multiform pore structure have been synthesized by a simple low temperature carbonization process. Biorenewable lignin was used as a cheap and carbon-rich precursor for the first time. The products were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, energy dispersive X-ray spectroscopy (EDS), vibrating sample magnetometer (VSM), transmission electron microscopy (TEM), and Raman spectrum. XRD pattern and Raman spectrum showed that the product has a high degree of graphitization crystallinity. TEM micrograph indicated that the synthesized MCNCs have the hierarchical pore and cage structure. Due to these characteristics, the obtained magnetic carbon nanocages can be used as efficient and recycled adsorbents in the removal of dye staff from textile wastewater.

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