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Abstract  

Pure silica zeolite ZSM-5 has been synthesised in a slightly acidic aqueous fluoride medium which produces the protonated form of the zeolite ZSM-5 [1]. Tetrahalometallate [2] species of cobalt and manganese have been synthesised and increasing mole fractions incorporated into the zeolite synthesis gel. The products have been analysed and characterised using simultaneous thermogravimetric-derivative thermogravimetric analysis (TG-DTG). The thermal decomposition, under nitrogen of the associated tetraethylammonium (TEA+) and tetrapropylammonium (TPA+) cations occluded within the zeolite channels is indicative and characteristic of the incorporation of the heteroatoms into the zeolitic framework. Analysis by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray fluorescence (XRF), and Fourier transform infrared spectroscopy (FTIR) has confirmed the reliability of thermogravimetric (TG) and derived thermogravimetric analysis (DTG) as a diagnostic tool.

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Abstract  

Binding properties and structural changes of human growth hormone (hGH) due to the interaction by cobalt ion (Co2+) were done at 27°C in NaCl solution, 50 mM, using different techniques of UV-Vis spectroscopy, circular dichroism (CD), isothermal titration calorimetry (ITC) and differential scanning calorimetry (DSC) techniques. There is a set of three identical and non-interacting binding sites for cobalt ions. The intrinsic association equilibrium constant and the molar enthalpy of binding obtained by ITC are 0.80 mM−1 and −16.70 kJ mol−1, respectively. The intrinsic association equilibrium constant obtained by a standard isothermal titration UV-Vis spectrophotometry method is also 0.79 mM−1, which is in good agreement with the value obtained from ITC. The Gibbs free energy and entropy changes due to the binding of cobalt ion on hGH are −16.67 kJ mol−1 and −0.1 J K−1 mol−1, respectively. Energetic domains analysis by DSC shows that phase transition of hGH in the presence of cobalt occurs at one main transition. Deconvolution of the main transition provides two sub-transitions with different values of the melting point and enthalpy of unfolding (33°C and 164 kJ mol−1 for the first and 49°C and 177 kJ mol−1 for the second, respectively). Interaction of cobalt ions with hGH prevents aggregation by an affect on the hydrophobicity of the protein macromolecule and provide useful information about its structure due to becoming reversible of protein thermal denaturation.

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Abstract

Cobalt nanoparticles were synthesized using continuous-flow (CF) chemistry in a stainless steel microreactor for the first time at high output based on the ethanol hydrazine alkaline system (EHAS) producing a yield as high as 1 g per hour [1, 2]. Continuous-flow (CF) synthetic chemistry provides uninterrupted product formation allowing for advantages including decreased preparation time, improved product quality, and greater efficiency. This successful synthetic framework in continuous-flow of magnetic Co nanoparticles indicates feasibility for scaled-up production. The average particle size by transmission electron microscopy (TEM) of the as-synthesized cobalt was 30±10 nm, average crystallite size by Scherrer analysis (fcc phase) was 15±2 nm, and the estimated magnetic core size was 6±1 nm. Elemental surface analysis (X-ray photoelectron spectroscopy [XPS]) indicates a thin CoO surface layer. As-synthesized cobalt nanoparticles possessed a saturation magnetization (M s) of 125±1 emu/g and coercivity (H c) of 120±5 Oe. The actual M s is expected to be greater since the as-synthesized cobalt mass was not weight-corrected (nonmagnetic mass: reaction by-products, solvent, etc.). Our novel high-output, continuous-flow production (>1 g/hr) of highly magnetic cobalt nanoparticles opens an avenue toward industrial-scale production of several other single element magnetic nanomaterials.

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Journal of Thermal Analysis and Calorimetry
Authors: D. Melo, F. Borges, F. Lima, H. Scatena, L. Zinner, V. Fernandes, W. Souza and Z. Silva

Abstract  

In this work, a cobalt complex with dmit (1,3-dithiol-2-thione-4,5-dithiolate) as ligand was prepared and its thermal stability was studied by thermogravimetric analysis and kinetics by means of the Zsak method and a non-linear method. For both methods, numerical binomial and polynomial filters were used, where points in the central interval were utilized.

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Abstract  

Molybdotellurates [M(H2O)6]3[TeMo6O24], with M=Ni(II) and Co(II), were synthesized and characterized by single-crystal X-ray diffraction for compound 1 and X-ray powder diffraction for compound 2, EDAX, IR, electronic spectra in the solid phase and in solution, and magnetic properties. Thermogravimetry and differential scanning calorimetry of both compounds revealed a loss of 11 water molecules through an endothermal process with ΔH=800 kJ mol−1 for the nickel compound and ΔH=833 kJ mol−1 for the cobalt compound. The residual compounds were characterized by chemical analysis, IR and XPS spectroscopy

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Azooz, M. M. (2009): Antioxidant potentials protect Vigna radiata (L.) Wilczek plants from soil cobalt stress and improve growth and pigment composition. - Plant Omics J. 2 (3): 120–126. Azooz M M

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Introduction Fischer–Tropsch synthesis (FTS) is a part of gas-to-liquids (GTL) technology, which produces clean fuels from natural gas. Cobalt-based FTS catalysts are usually preferred for the synthesis of long-chain paraffins

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Introduction Raney metal type catalysts are prepared by leaching the reactive material out from alloys of catalytically active transition metals such as nickel, cobalt, iron, copper and a reactive material such as aluminum with

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Reaction Kinetics, Mechanisms and Catalysis
Authors: Soipatta Soisuwan, Benjamas Netiworaruksa, Channarong Charoendechanukor, Tassanee Tubcharoen, Joongjai Panpranot and Piyasan Praserthdam

, the potential commercial cobalt catalysts are typically composed of four components: Co metal, a small amount of a second metal, oxide promoters (alkali, rare earth, and/or transition metal oxide such as ZrO 2 ) and supports (silica, alumina or titania

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Abstract  

Sorption of Co on bentonite has been studied by using a batch technique. Distribution coefficients (K d) were determined for the bentonite-cobalt solution system as a function of contact time, pH, sorbent and sorbate concentration and temperature. Sorption data have been interpreted in terms of Freundlich, Langmuir and Dubinin-Radushkevich equations. Thermodynamic parameters for the sorption system have been determined at three different temperatures. The positive value of the heat of sorption, H 0=22.08 kJ/mol at 298 K shows that the sorption of cobalt on bentonite is endothermic, where as the negative value of the free energy of sorption, G 0=–10.75 kJ/mol at 298 K shows the spontaneity of the process. G 0 becomes more negative with an increase in temperature which shows that the sorption process is more favourable at higher temperatures. The mean free energyE 7.7 kJ/mol for sorption of cobalt on bentonite shows that ion-exchange is the predominant mode of sorption in the concentration range of the metal studied i.e. 0.01 to 0.3 mol/dm3. The presence of some complementary cations depress the sorption of cobalt on bentonite in the order of K+>Ca2+>Mg2+>Na+. Some organic complexing agents and natural ligands also affect the sorption of cobalt. The desorption studies with ground water at low cobalt loadings on bentonite show that about 97% metal is irreversibly sorbed.

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