Search results for "Thermogravimetry"
showing 10 items of 150 documents
Conversion of Organic Dyes into Pigments: Extraction of Flavonoids from Blackberries (Rubus ulmifolius) and Stabilization
2021
The blackberry’s color is composed mainly of natural dyes called anthocyanins. Their color is red–purple, and they can be used as a natural colorant. Anthocyanins are flavonoids, which are products of plants, and their colors range from orange and red to various shades of blue, purple and green, according to pH. In this study, the chemical composition of an extract obtained from blackberries was defined by LC-ESI/LTQOrbitrap/MS in positive and negative ionization mode. Furthermore, we investigated the adsorption process of blackberry extract using several inorganic fillers, such as metakaolin, silica, Lipari pumice, white pozzolan and alumina. The pigments exhibit different colors as a func…
Halloysite nanotubes sandwiched between chitosan layers: novel bionanocomposites with multilayer structures
2018
This work is a contribution to the design of multilayer biocomposites based on halloysite nanotubes (HNTs) and chitosan. Both the polymer and nanotubular inorganic additive have been selected among easily available green materials. An innovative preparation procedure based on the sequential casting of chitosan and HNTs has been proposed in order to obtain multilayer composite biofilms. A physico-chemical investigation (contact angle measurements, differential scanning calorimetry, thermogravimetry) has been conducted to characterize the bionanocomposites. As evidenced by scanning electron microscopy, the nanocomposites possess an intermediate halloysite layer between the chitosan ones. The …
Characterization and utilization of MFI zeolites and MCM-41 materials for gaseous pollutant adsorption
1999
Physisorption of n-hexane, trichloroethylene, tetrachloroethylene, carbon and nitrogen oxides on a microporous ZSM-5 (Si/Al=339) zeolite and an amorphous mesoporous MCM-41 (Si/Al=∞) sample was examined by isothermal thermogravimetry, manometry and calorimetry to evaluate the feasibility of using these porous materials for gaseous pollutant adsorption at room temperature. The adsorbents showed very interesting adsorption properties for hydrocarbons. ZSM-5 exhibited the strongest adsorption affinity and MCM-41 showed the largest adsorption capacity. Another main feature in this work was to observe a stepped-isotherm for the adsorption of C2Cl4 on ZSM-5. Such a substep located at very low rela…
A new approach to the synthesis of intermetallic compounds: mild synthesis of submicrometric CoxMy (M = Mo, W; x∶y = 3∶1 and 7∶6) particles by direct…
2002
A simple processing route to cobalt–molybdenum and cobalt–tungsten intermetallics (CoxMy, where M = Mo and W, and x∶y = 3∶1 and 7∶6) has been developed, on the basis of the use of precursors resulting from freeze-drying of aqueous solutions of the appropriate common metal salts. The influence of the preparative variables on the outcomes of this procedure is examined. These compounds are prepared as single phases by thermal reduction of amorphous freeze-dried powders under a hydrogen–argon atmosphere (8% H2), followed by slow cooling of the samples. The materials have been characterised by X-ray powder diffraction, metal analysis, scanning electron microscopy and thermogravimetry under an ox…
Cadmium(II) complexes of cytosine
1990
Complexes of cadmium(II) with cytosine obtained from aqueous or physiological solutions at room temperature are reported. The complexes were characterized by spectroscopic, conductometric,1H-NMR, and13C-NMR measurements and also by thermogravimetry.
Synthesis of new vanadium–chromium and chromium–molybdenum oxynitrides by direct ammonolysis of freeze-dried precursors
2000
Interstitial vanadium–chromium and chromium–molybdenum oxynitrides in the solid solution series V1 − zCrz(OxNy) and Cr1 − zMoz(OxNy) (z = 0.0, 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) have been obtained by direct ammonolysis of precursors resulting from the freeze-drying of aqueous solutions of the appropriate metal salts. A study of the influence of the preparative variables on the outcomes of this procedure is presented. Compounds in the V1 − zCrz(OxNy) series are prepared as single phases by nitridation at 1073 K, followed by fast cooling of the samples. Compounds in the Cr1 − zMoz(OxNy) series are prepared as nearly single phases by nitridation at different temperatures, optimized for each composi…
Influence of drying to the structure of lactitol monohydrate
1997
The purpose of this study is to find out the effect of the crystal water content on the crystal structure of lactitol monohydrate. Crystal water was removed by drying over silicagel at 40°C and by using phosphorus pentoxide as drying agent at 20°C. The amouts of water removals were identified by thermogravimetry, the melting points and the heat of fusions were calculated from the results of differential scanning calorimetry measurements and the structure of samples were identified by X-ray powder diffraction method. Over 23 w/w% of total water content could removed by gently drying until significant structural changes could be detected. The melting point of anhydrous lactitol obtained by dr…
Effect of some additives on the reactions in fly ASH-Ca(OH)2system
2004
Differential thermal analysis and thermogravimetry were used to evaluate the effect of some additives, such as CaSO4, CaCl2 and silica fume amorphous silica from ferrosilicon synthesis on the mechanism and kinetics of reactions occurring in fly ash-Ca(OH)2 system. The accelerating role of these additives was demonstrated from the data relating to Ca(OH)2 consumption in hydrated pastes, determined by TG measurements.
Gravimetric characterisation of the surface properties of a porous drug carrier
1995
The gas adsorption method is the most common means to characterise the topology of solid surfaces with regard to its use as an adsorbent. Adsorption isotherms are determined advanta-geously using a vacuum microbalance: Thermogravimetric techniques allow the observation of sample degassing and its optimization. The dry mass is determined in situ, the mass of gas adsorbed is measured directly and different gases can be used without calibration. From the isotherm the pore size distributions, specific surface area, fractal dimension and density can be derived. Commercially available gravimetric sorption apparata and vacuum balances as well as software for data evaluation are reviewed in tables.…
Gravimetric and FTIR study of the interaction of tetramethylethylene on a MFI zeolite
2005
The adsorption of tetramethylethylene on a high siliceous ZSM-5 zeolite was performed by thermogravimetry, in situ FTIR spectroscopy and molecular dynamics simulation. Sorption and spectroscopic data were analysed as a function of loading and compared with molecular dynamics simulated results to characterize the adsorption process. The isotherm at 298 K does not show any deviation from the type I behaviour. The presence of admolecules in micropores does not or weakly affect zeolite framework vibration bands but induces an additional band at around 1715 cm−1 mainly due to a contribution of the microporous surface of the adsorbent. A confinement effect of the adsorbate is characterized during…