Search Results

You are looking at 1 - 6 of 6 items for

  • Author or Editor: Flavio Carvalho x
  • All content x
Clear All Modify Search
Journal of Thermal Analysis and Calorimetry
Authors: Marilda Vianna, Jo Dweck, Frank Quina, Flavio Carvalho, and Claudio Nascimento

Abstract  

This study investigates the sorption of toluene and naphthalene by a sodium bentonite (BFN), an organoclay (WS35) and by their respective iron oxide hydrate composites Mag_BFN and Mag_S35. The organic matter content of WS35 and Mag_S35, determined by thermogravimetry, was used to obtain their organic matter sorption coefficients, which show that they are effective sorbents to remove organic contaminants from water, with a higher selectivity for naphthalene than for toluene sorption. The main iron oxide phase present in Mag_BFN and Mag_S35 is maghemite (γ-Fe2O3), which allows these sorbents to be separated from the effluent by a magnetic separation process after use.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Marilda Vianna, Jo Dweck, Frank Quina, Flavio Carvalho, and Claudio Nascimento

Abstract  

Commercial bentonite (BFN) and organoclay (WS35), as well as iron oxide/clay composite (Mag_BFN) and iron/oxide organoclay composite (Mag_S35) were prepared for toluene and naphthalene sorption. Mag_BFN and Mag_S35 were obtained, respectively, by the precipitation of iron oxide hydrates onto sodium BFN and S35 clay particles. The materials were characterized by powder X-ray diffraction (XRD), X-ray Fluorescence (XRF), and TG and DTA. From XRF results and TG data on calcined mass basis, a quantitative method was developed to estimate the iron compound contents of the composites, as well as the organic matter content present in WS35 and Mag_S35.

Restricted access

Abstract  

In the present work, the thermal behavior of prednicarbate was studied using DSC and TG/DTG. The solid product remaining at the first decomposition step of the drug was isolated by TG, in air and N2 atmospheres and was characterized using LC-MS/MS, NMR, and IR spectroscopy. It was found that the product at the first thermal decomposition step of prednicarbate corresponds to the elimination of the carbonate group bonding to C17, and a consequent formation of double bond between C17 and C16. Structure elucidation of this degradation product by spectral data has been discussed in detail.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Ronaldo S. Nunes, Gilbert Bannach, José M. Luiz, Flávio J. Caires, Claudio T. Carvalho, and Massao Ionashiro

Abstract

Solid-state compounds of general formula Ln2L3·nH2O, where L represents 1,4-bis(3-carboxy-3-oxo-prop-1-enyl)benzene and Ln = La, Ce, Pr, Nd, Sm, were synthesized. Complexometric titrations with EDTA, thermogravimetry (TG), differential thermal analysis (DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, elemental analysis and infrared spectroscopy have been employed to characterize and to study the thermal behavior of these compounds in dynamic air atmosphere. The results led to information about the composition, dehydration, crystallinity, and thermal decomposition of the synthesized compounds.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Gabriel de Araujo, Dalva de Faria, Márcio Zaim, Flávio de Souza Carvalho, Fabio de Andrade, and Jivaldo Matos

Abstract  

Tibolone polymorphic forms I (monoclinic) and II (triclinic) have been prepared by recrystallization from acetone and toluene, respectively, and characterized by different techniques sensitive to changes in solid state, such as polarized light microscopy, X-ray powder diffractometry, thermal analysis (TG/DTG/DSC), and vibrational spectroscopy (FTIR and Raman microscopy). The nonisothermal decomposition kinetics of the obtained polymorphs were studied using thermogravimetry. The activation energies were calculated through the Ozawa’s method for the first step of decomposition, the triclinic form showed a lower E a (91 kJ mol−1) than the monoclinic one (95 kJ mol−1). Furthermore, Raman microscopy and DSC at low heating rates were used to identify and follow the thermal decomposition of the triclinic form, showing the existence of three thermal events before the first mass loss.

Restricted access
Journal of Thermal Analysis and Calorimetry
Authors: Mauro da Silva, Flávio de Souza Carvalho, Tereza da Silva Martins, Márcia de Abreu Fantini, and Paulo Isolani

Abstract

Two series of lanthanide oxides with different morphologies were synthesized through calcinations of two types of citrate polymeric precursors. These oxides were characterized by XRD patterns, SEM electronic microscopy, and N2 adsorption isotherms. SEM microscopy analysis showed that the calcination of crystalline fibrous precursors [Ln2(LH)3·2H2O] (L = citrate) originated fibrous shaped particles. On the other hand, the calcination of irregular shaped particles of precursors [LnL·xH2O] originated irregular shaped particles of oxide, pointing out a morphological template effect of precursors on the formation of the respective oxides.

Restricted access