scholarly journals Catalytic Decomposition of H2O2 over Pure and Li2O-Doped Co3O4 Solids

1998 ◽  
Vol 16 (9) ◽  
pp. 733-746 ◽  
Author(s):  
Gamil A. El-Shobaky ◽  
Nagi R.E. Radwan ◽  
Farouk M. Radwan
Keyword(s):  
Heat Treatment ◽  
Specific Surface ◽  
Catalytic Decomposition ◽  
Nitrogen Adsorption ◽  
Progressive Increase ◽  
Lithium Oxide ◽  
Lithium Nitrate ◽  
Surface Areas ◽  
Catalytically Active ◽  
Cobaltic Oxide

Pure and doped Co3O4 samples were prepared by the thermal decomposition at 500–900°C of pure and lithium nitrate-treated basic cobalt carbonate. The amounts of dopant added were varied in the range 0.75–6 mol% Li2O. The effects of this treatment on the surface and catalytic properties of cobaltic oxide solid were investigated using nitrogen adsorption at −196°C and studies of the decomposition of H2O2 at 30–50°C. The results obtained revealed that Li2O doping of Co3O4 followed by heat treatment at 500°C and 600°C resulted in a progressive increase in the value of the specific surface area, SBET, to an extent proportional to the amount of dopant present. However, the increase was more pronounced in the case of solid samples calcined at 500°C. This increase in the specific surface areas has been attributed to the fixation of a portion of the dopant ions on the uppermost surface layers of the solid leading to outward growth of the surface lattice. The observed increase in SBET due to Li2O doping at 500°C might also result from a narrowing of the pores in the treated solid as a result of the doping process. Lithium oxide doping of cobaltic oxide followed by heat treatment at 700–900°C resulted in a significant decrease in the SBET, Vp and r̄ values. Pure and doped solids precalcined at 500°C and 600°C exhibited extremely high catalytic activities which were not much affected by doping with Li2O. On the other hand, doping followed by calcination at 700–900°C brought about a considerable and progressive increase in the catalytic activity of the treated solids. This treatment did not modify the activation energy of the catalysed reaction, i.e. doping of Co3O4 solid followed by heating at 700°C and 900°C did not alter the mechanism of the catalytic reaction but increased the concentration of catalytically active constituents taking part in the catalytic process without altering their energetic nature.

scholarly journals Study of sepiolite from Goles (Kosovo, Yugoslavia). II. Acid activation

2002 ◽  
Vol 67 (7) ◽  
pp. 499-506 ◽  
Author(s):  
Marina Radojevic ◽  
Vidojko Jovic ◽  
Dragomir Karaulic ◽  
Dragomir Vitorovic
Keyword(s):  
Specific Surface ◽  
Chemical Treatment ◽  
Acid Treatment ◽  
Nitrogen Adsorption ◽  
Adsorption Properties ◽  
Acid Activation ◽  
Surface Areas ◽  
Bet Method ◽  
Specific Surface Areas ◽  
Enhanced Adsorption

The changes in the pore structure and adsorption properties of sepiolite from Goles resulting from treatment with 4MHCl for various periods of time were investigated. The BET method specific surface areas, pore volumes and f ? plots were determined by nitrogen adsorption. The surface area progressively increased during the 70 hours of acid treatment, when a maximum was attained. The differences in the adsorption properties of the original and the acid treated sepiolite were evaluated by comparison of adsorption isotherms obtained with benzene, n-hexane, methanol and isooctane. The enhanced adsorption of isooctane was of great interest, since the sorption of this compound on natural sepiolites is generally very limited. The results suggest that chemical treatment of sepiolite with 4MHCl for 70 h produces an adsorbent of optimal porosity and other adsorption properties.

Elimination of Chromium (VI) by Adsorption onto Natural and/or Modified Kaolinite

2018 ◽  
Vol 18 ◽  
pp. 106-112 ◽  
Author(s):  
Nouel Hezil ◽  
Mamoun Fellah ◽  
Omar Assala ◽  
Mohamed Zine Touhami ◽  
Kamel Guerfi
Keyword(s):  
Specific Surface ◽  
Cationic Surfactant ◽  
Interlayer Space ◽  
Nitrogen Adsorption ◽  
Surface Areas ◽  
Chromium Vi ◽  
Two Samples ◽  
Modification Method ◽  
Aqueous Effluents ◽  
Chromate Ion

The purpose of this study is to compare the effectiveness of a natural and / or modified kaolinite to adsorb chromium-containing aqueous effluents in its most toxic form (the hexavalent chromate ion (Cr (VI)). Adsorbant used in the present study is a kaolinite of hydrothermal origin. The modified kaolinite has been prepared by insertion of a cationic surfactant DTAC in interlayer space of this clay. The modification method is generally performed by the cation exchange reaction in the liquid state. The specific surface areas determined by nitrogen adsorption at 77 K for the two samples of kaolinite (natural and modified) are succinctly 48.75 and 63.72 m2/g. Scanning electron microscopy has shown that the used clay is in tubular form. The treatment of natural kaolin by the intercalation of cationic surfactant increased its specific surface of about 18 %. Therefore its power sorptif increased which was found by a comparative study of adsorption of Cr (VI) on natural kaolin and / or modified.

Nitrogen adsorption on synthetic akaganeite and its structural implications

Clay Minerals ◽  
1977 ◽  
Vol 12 (4) ◽  
pp. 345-352 ◽  
Author(s):  
E. Paterson ◽  
J. M. Tait
Keyword(s):  
Specific Surface ◽  
Electron Micrographs ◽  
Nitrogen Adsorption ◽  
Structural Scheme ◽  
Qualitative And Quantitative ◽  
Surface Areas ◽  
Two Samples ◽  
Specific Surface Areas ◽  
Adsorptive Properties ◽  
Quantitative Assessments

AbstractComparison of the adsorptive properties of two samples of akaganéite prepared by different methods shows that a structural scheme based upon solid rods is much more likely than a previously proposed scheme involving tubes. Specific surface areas, qualitative and quantitative assessments of porosity' and electron micrographs strongly support this structure.

scholarly journals Sorption of Methylene Blue for Studying the Specific Surface Properties of Biomass Carbohydrates

Coatings ◽  
2020 ◽  
Vol 10 (11) ◽  
pp. 1115
Author(s):  
Tatiana Skripkina ◽  
Ekaterina Podgorbunskikh ◽  
Aleksey Bychkov ◽  
Oleg Lomovsky
Keyword(s):  
Methylene Blue ◽  
Specific Surface ◽  
Surface Area ◽  
Surface Characterization ◽  
Gas Adsorption ◽  
Comparative Method ◽  
Nitrogen Adsorption ◽  
Surface Areas ◽  
Nitrogen Adsorption Isotherms ◽  
Adsorption Desorption

The surface area is an important parameter in setting any biorefining technology. The aim of this study was to investigate the applicability of sorption of methylene blue to characterize the surface of the main biomass carbohydrates: α-cellulose, sigmacell cellulose, natural gum, β-glucan, and starch. The morphology of particles of the model objects was studied by scanning electron microscopy. Nitrogen adsorption isotherms demonstrate that the selected carbohydrates are macroporous adsorbents. The monolayer capacities, the energy constants of the Brunauer–Emmett–Teller (BET) equation, and specific surface areas were calculated using the BET theory, the comparative method proposed by Gregg and Sing, and the Harkins–Jura method. The method of methylene blue sorption onto biomass carbohydrates was adapted and mastered. It was demonstrated that sorption of methylene blue proceeds successfully in ethanol, thus facilitating surface characterization for carbohydrates that are either soluble in water or regain water. It was found that the methylene blue sorption values correlate with specific surface area determined by nitrogen adsorption/desorption and calculated from the granulometric data. As a result of electrostatic attraction, the presence of ion-exchanged groups on the analyte surface has a stronger effect on binding of methylene blue than the surface area does. Sorption of methylene blue can be used in addition to gas adsorption/desorption to assess the accessibility of carbohydrate surface for binding large molecules.

scholarly journals Structural and Textural Studies of ZnO Modified with Dodecyltrimethylammonium Chloride

1998 ◽  
Vol 16 (6) ◽  
pp. 465-485 ◽  
Author(s):  
Christine A. Philip
Keyword(s):  
Heat Treatment ◽  
Thermal Treatment ◽  
Cationic Surfactant ◽  
Structural Changes ◽  
Nitrogen Adsorption ◽  
Aqua Complex ◽  
Carbonate Complex ◽  
Oh Groups ◽  
Surface Areas ◽  
Dodecyltrimethylammonium Chloride

The effect of dodecyltrimethylammonium chloride — a cationic surfactant — on the texture and structure of ZnO, which is commonly used in the photocatalytic degradation of surfactants, has been investigated together with the effect of thermal treatment of the resulting materials at temperatures ≤350°C. Structural changes were followed by combining diffraction and infrared (IR) spectroscopic measurements while textural variations were monitored via low-temperature nitrogen adsorption studies. In addition, the effect of soaking the original sample of ZnO in water for 5 d has been monitored together with the effect of heat treatment on the resulting products. Bands corresponding to a carbonate complex were observed in the IR spectrum of all samples subjected to thermal treatment below 275°C. This complex gave rise to new bands in the XRD patterns of such samples situated at d-distances of 2.339, 2.023 and 1.431 Å, respectively, which disappeared when the samples were subjected to heat treatment above 275°C. The intensities of such bands decreased when increasing surfactant concentrations were employed in the initial treatment of the ZnO solid. Acid OH groups on the surface of the solid appear to provide sites for the formation of the carbonate complex. Such sites are attacked either by the aqua complex [Zn(H2O)6]2+ formed from dissolved ZnO in the presence of water alone or by the cationic surfactant when the latter is present in the system. Attack of the surfactant on the surface probably occurs through exchange with an H+ ion. The cationic surfactant was also adsorbed on to basic sites present on the surface of the solid since the concentration of such sites diminished as the surfactant concentration was increased. Measurements of the specific surface areas and pore structural analyses for all the samples studied indicated the presence of micro- and meso-pores in most cases, the former being absent from the parent ZnO employed. A comparison between the application of the V l versus t plot and the α s-plot for such pore structural analyses is presented together with a discussion of the criteria necessary for the application of the αs-method.

scholarly journals Adsorption of water vapour and the specific surface area of arctic zone soils (Spitsbergen)

2018 ◽  
Vol 32 (1) ◽  
pp. 19-27 ◽  
Author(s):  
Jolanta Cieśla ◽  
Zofia Sokołowska ◽  
Barbara Witkowska-Walczak ◽  
Kamil Skic
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Water Vapour ◽  
Specific Surface Area ◽  
Nitrogen Adsorption ◽  
Total Carbon ◽  
Arctic Zone ◽  
Surface Areas ◽  
Arctic Soils ◽  
Specific Surface Areas

AbstractWater vapour/nitrogen adsorption were investigated and calculated the specific surface areas of arctic-zone soil samples (Turbic Cryosols) originating from different micro-relief forms (mud boils, cell forms and sorted circles) and from different depths. For the characterisation of the isotherms obtained for arctic soils, the Brunauer-Emmet-Teller model was then compared with the two other models (Aranovich-Donohue and Guggenheim-Anderson-de Boer) which were developed from Brunauer-Emmet-Teller. Specific surface area was calculated using the Brunauer-Emmet-Teller model at p p0−1range of 0.05-0.35 for the water vapour desorption and nitrogen adsorption isotherms. The values of total specific surface area were the highest in Cryosols on mud boils, lower on cell forms, and the lowest on sorted circles. Such tendency was observed for the results obtained by both the water vapour and nitrogen adsorption. The differences in the values of specific surface area at two investigated layers were small. High determination coefficients were obtained for relationships between the specific surface areas and contents of clay and silt fraction in Cryosols. No statistically significant correlation between the total carbon amount and the values of specific surface area in Cryosols has been found.

Synthesis of Ytterbium Sulfides by the Sulfurization and Heat Treatment

2015 ◽  
Vol 655 ◽  
pp. 224-229 ◽  
Author(s):  
Liang Li ◽  
Shinji Hirai ◽  
Hai Bin Yuan ◽  
Eiji Nakamura
Keyword(s):  
Heat Treatment ◽  
Specific Surface ◽  
Single Phase ◽  
Polymorphic Form ◽  
Particle Sizes ◽  
Orthorhombic Structure ◽  
Surface Areas ◽  
Plasma Sintering ◽  
Heat Treated ◽  
Spark Plasma

Single-phase ytterbium sulfides (Yb2S3 and YbS) were synthesized by sulfurization of Yb2O3 with CS2 gas and heat treatments. Four kinds of Yb2O3 powders with different particle sizes and specific surface areas were employed as starting materials. When specific surface area of Yb2O3 powder is about 50 m2/g, a new polymorphic form Yb2S3 with an orthorhombic structure could be obtained by the sulfurization at 600°C for 8 hr. Single-phase hexagonal Yb2S3 was also synthesized form former three kinds of Yb2O3 powders by sulfurization above 1000 °C for 8 hr. Subsequently, the synthesized Yb2S3 powders were heat-treated under different conditions. Upon heat treatment at 1000 °C for 3 hr in Ar/CS2 atmosphere, orthorhombic Yb2S3 phase underwent phase transition to hexagonal Yb2S3 phase. Moreover, XRD results showed that orthorhombic Yb3S4 was main phase after heat treatment at 1050°C for 8 hr under Ar atmosphere and Yb2S3 disappeared upon prolonged (12 hr) heat treatment. Single Yb3S4 phase could be obtained after treatment at 1000 °C for 3 hr, or at 1200 °C for 1 hr, under vacuum (~1.2×10-3 Pa). YbS was formed upon treatment at 1200 °C for 5 hr. Single-phase YbS with a homogeneity range of YbS1.11-1.15 could be synthesized by treatment at 1500 °C for 3 hr. PartialYb2S3 transformed to Yb3S4 at 1300 °C for 1 hr by spark plasma sintering.

Effect of Heat-Treatment on the Microstructure and Properties of SiO2-TiO2 Aerogels Synthesized via Supercritical Drying

2016 ◽  
Vol 848 ◽  
pp. 770-776 ◽  
Author(s):  
Yong Gang Jiang ◽  
Yan Qing Qin ◽  
Jun Zong Feng ◽  
Jian Feng ◽  
Lin Xu
Keyword(s):  
Heat Treatment ◽  
Specific Surface ◽  
Three Dimensional ◽  
Supercritical Drying ◽  
High Specific Surface Area ◽  
Sem Images ◽  
Average Pore ◽  
Microstructure And Properties ◽  
Surface Areas ◽  
Heat Treated

Monolithic SiO2-TiO2 aerogels were prepared via supercritical drying using tetraethoxysilane and tetrabutyltitanate as precursors and ethanol as solvent. Influence of the heat-treatment on the microstructure and properties of SiO2-TiO2 aerogels were investigated in detail. The results showed that the as-prepared SiO2-TiO2 aerogels had low densities, high specific surface areas, small average pore diameters, and three-dimensional nanoporous structures. The anatase TiO2 phase of SiO2-TiO2 aerogels could form during supercritical drying process, and the transition to rutile TiO2 phase occurred after experiencing 1200°C for 2 h. SiO2-TiO2 aerogels containing 30 wt% TiO2 (ST3) still presented relatively high specific surface area of 451 m2/g even they undergo the treatment of 1000°C for 2 h. And the SEM images indicated that the agglomerated particles derived from ST3 appeared gradually to some extent. The glassy luster of ST3 heat-treated at 1200°C for 2 h illuminates SiO2 started to vitrify. Besides, the thermal conductivity of ST3 at room temperature is up to 0.03257 W·m-1·K-1.

scholarly journals Preparation Method of Co3O4Nanoparticles Using Degreasing Cotton and Their Electrochemical Performances in Supercapacitors

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Hongyan Xu ◽  
Libo Gao ◽  
Qiang Zhang ◽  
Junyang Li ◽  
Jiangtao Diwu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Specific Surface ◽  
Photoelectron Spectroscopy ◽  
Nitrogen Adsorption ◽  
Electrochemical Performances ◽  
X Ray ◽  
Surface Areas ◽  
Synthetic Strategy ◽  
Different Temperatures ◽  
Specific Surface Areas

Co3O4nanoparticles were fabricated by a novel, facile, and environment-friendly carbon-assisted method using degreasing cotton. Structural and morphological characterizations were performed using X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The component of the sample obtained at different temperatures was measured by Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Nitrogen adsorption and desorption isotherms were utilized to reveal the specific surface areas. The formation mechanism of Co3O4nanoparticles was also proposed, demonstrating that the additive degreasing cotton played an indispensable role in the process of synthesizing the sample. The resultant Co3O4sample calcined at 600°C exhibited superior electrochemical performance with better specific capacitance and long-term cycling life, due to its high specific surface areas and pores structures. Additionally, it has been proved that this facile synthetic strategy can be extended to produce other metal oxide materials (e.g., Fe3O4). As a consequence, the carbon-assisted method using degreasing cotton accompanied a promising prospect for practical application.

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