Characterization and kinetics analysis of the thermal decomposition of the humic substance from hazelnut husk

A humic substance was obtained from hazelnut husk using an alkali extraction. The chemical and morphological structure of the humic matter was characterized via elemental analysis, Fourier transform infrared spectrometry (FTIR), nuclear magnetic resonance, Brunauer-Emmet-Teller (BET) analysis, scanning electron microscopy (SEM), and thermogravimetric-FTIR (TG-FTIR). In addition, thermal analysis measurements TG analysis-differential thermogravimetry/differential scanning calorimetry (TGA-DTG/DSC) were performed under dynamic air conditions to better determine the origin, physical and chemical structure, and decomposition process of the humic matter. The Kissinger-Akahira-Sunose (KAS) and Flynn-Wall-Ozawa (FWO) methods were used to calculate the kinetic parameters of the high-temperature decomposition process. It was observed that the activation energy values were almost constant at certain conversion and temperature intervals. In addition, the structure of the humic substance at different temperatures was also investigated via FTIR analysis. It was found that the obtained humic substance had a very stable structure and decomposed at a high temperature. The stability of the humic matter can be a useful tool in the environmental quality research of soil.     

Non-isothermal Decomposition Kinetics of Complex of Co(III), Ni(II) with O,O'-dialkyldithiophosphates and Adducts of Ni-complex with Pyridines

Thermal behaviour of tri(O,O'-diisopropyldithiophosphate)cobalt(III), Co(dptp)₃ and bis (O,O'-diethyldithiophosphate)nickel(II), Ni(detp)₂ and its adducts with pyridine, Ni(detp)₂(py)₂ or 4-methylpyridine, Ni(detp)(mpy)₂ in a dynamic nitrogen atmosphere was investigated by TG-DTG and DSC techniques, which showed a medium endothermic peak for the evolution process of pyridine(or 4-methylpyridine) and a strong exothermic peak for that of O,O'-diethyldithiophosphate. The thermal stability and decomposition patterns for these compounds were compared and interpreted in terms of structural features such as bond character and steric effects. The kinetic parameters and mechanisms of every decomposition stage involved for all these complexes were obtained employing the non-isothermal kinetic analysis method suggested by Malek et al., which showed the kinetics mechanism for pyrolysis of pyridine(or 4-methylpyridine) is an S-B empirical model with lower activation energy, while that of O,O'-dialkyldithiophosphate is a diffusion model. These results are in accord with the fact that two ligands are of different type. This revised version was published online in August 2006 with corrections to the Cover Date.     

四(1-乙基咪唑)二异硫氰酸锰的晶体结构和热性能

A complex [Mn(NCS)₂(Eim)₄] (where Eim=1-ethylimidazole) has been synthesized and structurally cha-racterized by X-ray diffraction single-crystal structure analysis. The compound crystallizes in the Orthorhombic space group Pbca with the cell parameters: a=1.618 9(3) nm, b=1.787 4(4) nm, c=1.999 4(4) nm, and V=5.786(2) nm³, Z=8. In the structure, each Mn atom is coordinated by four Eim ligands and a pair of monodentate isothiocyanic groups, affording a compressed octahedral MnN₆ core. The NCS^- anions are trans and four N atoms from the Eim ligands define the equatorial plane. The C-H…π supramolecular interactions between C-H and imidazole rings of Eim link the molecules into independent chains running along the c-axis. The thermal gravity(TG) data indicates that thermal decomposition of the title complex takes place in two steps, the residue is Fe. CCDC: 646113.     

Molar heat capacity and thermodynamic properties of crystalline Ho(Asp)Cl<Subscript>2</Subscript>·6H<Subscript>2</Subscript>O

The molar heat capacity, C _p,m, of a complex of holmium chloride coordinated with L-aspartic acid, Ho(Asp)Cl₂·6H₂O, was measured from 80 to 397 K with an automated adiabatic calorimeter. The thermodynamic functions H _T-H _298.15 and S _T-S _298.15 were derived from 80 to 395 K with temperature interval of 5 K. The thermal stability of the complex was investigated by differential scanning calorimeter (DSC) and thermogravimetric (TG) technique, and the mechanism of thermal decomposing of the complex was determined based on the structure and the thermal analysis experiment.     

p-CH3C6H4SR型硫醚与钯(II)配合物热分解反应动力学

热重分析(TG)和微商热重法(DTG)广泛应用于各个研究领域,用非等温热重法测定固体化合物的热分解动力学参数已有报导.许多作者提出各种不同的数据处理方法.本文用的ρ-CH_3C_6H_4SR 型硫醚对钯的萃取具有选择性好、分配比高、气味较小、易溶于脂肪烃类溶剂、易于合成、是很有发展前途的一类萃取剂.我们合成五种ρ-CH_3C_6H_4SR(R:n-C_4H_9,n-C_6H_(13),n-C_8H_(17),n-C_(10)H_(21),n-C_(12)H_(25))型硫醚与钯(Ⅱ)的配合物,用TG-DTG 法研究它们的热分解过程,用微商法(Freeman-Carroll 方程)及积分法(Coats-Redfern 方程)获得了这些配合物的热分解动力学参数.     

Adiabatic calorimetry and thermal analysis on acetaminophen

Molar heat capacities of acetaminophen were precisely measured with a small sample precision automated adiabatic calorimeter over the temperature range from 80 to 330 K. A solid-solid transition at 149.96 K was found from the C_p,m-T curve. The polynomial functions of C_p,.m(J K^-1 mol^-1) vs. T were established on the heat capacity measurements by means of the least square fitting method. Thermal decomposition processes of acetaminophen have been studied by thermogravimetry. And the thermal decomposition kinetics parameters, such as activation energy E, pre-exponential factor A and reaction order n, were calculated by TG-DTG techniques with the Freeman-Carroll method, Kissinger method and Ozawa method. Accordingly the thermal decomposition kinetics equation of acetaminophen is expressed as: dα/dt=2.67·10⁷e^-89630/RT(1-α)^0.23. The process of fusion has been investigated through DSC. The melting point, molar enthalpy and entropy of fusion are to be (441.89±0.04) K, 26.49±0.44 kJ mol^-1 and 59.80±1.01 J K^-1 mol^-1, respectively.     

Kinetics of the Complex of Terbium o-methylbenzoate with 1,10-Phenanthroline. Synthesis,decomposition mechanism

The complex of [Tb₂(o-MBA)₆(PHEN)₂] (o-MBA: o-methylbenzoate and PHEN:1,10-phenanthroline) were synthesized and characterized by elemental analysis and IR spectroscopy. The thermal behavior of [Tb₂(o-MBA)₆(PHEN)₂] in dynamic nitrogen atmosphere was investigated by TG-DTG techniques. The thermal decomposition process of the [Tb₂(o-MBA)₆(PHEN)₂] occurred in three consecutive stages at T_p 294, 427 and 512°C. The kinetic parameters and mechanisms of first decomposition stage from analysis of the TG-DTG curves were obtained by the Malek method. This revised version was published online in August 2006 with corrections to the Cover Date.     

Low Temperature Heat Capacities and Thermodynamic Properties of Zinc L-Threonate Zn(C_4H_7O_5)_2(s) by Adiabatic Calorimetry

Low-temperature heat capacities of the solid compound Zn(C4H7O5)2(s) were measured in a temperature range from 78 to 374 K, with an automated adiabatic calorimeter. A solid-to-solid phase transition occurred in the temperature range of 295?322 K. The peak temperature, the enthalpy, and entropy of the phase transition were determined to be (316.269±1.039) K, (11.194±0.335) kJ?mol-1, and (35.391±0.654) J?K-1?mol-1, respectively. The experimental values of the molar heat capacities in the temperature regions o...     

Simultaneous Determinations of Fe2+ and Fe3+ in Ferrous Sulfate Destined for Pharmaceutical Preparations

ABSTRACT

Only the simultaneous analysis of the amount of Fe^2? and the possible presence of Fe³⁺ in ferrous sulfate heptahydrated (FeSO_4. 7 H₂O) can guarantee covered tablets, drops or syrups with insured quality. This work suggests that these analysis are accomplished through spectrophotometric method by use of the 1, 10-phenanthroline as chelate. Thus, at 510 nm the absorption is only due to the complex of the ligand with Fe^2? and at 390 nm the absorption is indicative of Fe^2+/3+ coordinated. Pharmaceutical raw matter and covered tablets were analyzed. Techniques of thermogravimetric analysis (TG-DTG) were used for the knowledge of the regions of loss of water of the FeSO₄. 7 H₂O for the relationship to its stoichiometry.     

TG-DTG as an effective method for the characterization of rutin extracted from the buds of <Emphasis Type="Italic">Sophora japonica</Emphasis> L.

The thermal behavior of rutin extracted from the buds of Sophora japonica L. by different methods and conditions have been investigated using TG and DTG. The results showed that every sample had different mass loss, curve shape, and peak location related to varied extraction technology. The TG-DTG characteristics of the rutin sample extracted by alkali-dissolution and acid-sedimentation with the solution adjusted to pH 9 and simply borax as stabilizer were highly similar to that of standard rutin, with the maximal purity determined by spectrophotometry. Therefore, the TG-DTG patterns could be served to characterize rutin extracted from the buds of Sophora japonica L.