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1.
The nature of recalcitrant organic carbon (OC) in soil is a matter of
great debate and various chemical treatments exist for its isolation. We compared
calorimetric properties from silt+clay fractions of eight mineral soils by
means of DSC before and after chemical oxidation with sodium hypochlorite
(NaOCl) to find out, whether recalcitrance of soil organic matter against
chemical oxidation coincides with its thermal stability. NaOCl oxidized around
75% of the OC, which corresponded well to a mean loss in heat of reaction
of 80%. Peak temperatures and 50% burnoff temperatures did not change systematically
after oxidation showing that the thermal stability of NaOCl residues was similar
to that of untreated samples. Three samples revealed peaks at >520°C after
oxidation indicative for the presence of pyrogenic carbon. 相似文献
2.
A. J. M. Barros S. Prasad V. D. Leite A. G. Souza G. Marino Crislene R. S. Morais Marta M. Conceição 《Journal of Thermal Analysis and Calorimetry》2007,87(3):685-689
The present study was carried out for evaluating the retention behavior
of sanitary sewage in relation to cadmium and cobalt ions in an ascendant
continuous-flow reactor. It was found that the studied sludge presented a
high assimilation of the metals, probably due to the presence of anionic groups,
which favors adsorption and complexation processes. Thermal analyses of the
samples showed a shift in the thermal decomposition of the ‘in natura’
sludge, when compared with those of the samples spiked with the metals, confirming
the possibility of interactions between the heavy metals and the anionic groups
present in the sludge. 相似文献
3.
Jane E. Callanan 《Journal of Thermal Analysis and Calorimetry》1995,45(3):359-368
The temperature and enthalpy of fusion of silver were measured in a differential thermal analyzer with gold and aluminum as
reference materials. The measurement procedures and the data calibration (or correction) procedures used successfully in our
laboratory for differential scanning calorimetry were applied. The experimental fusion temperature, (1233.9±1.0)K, and enthalpy,
(108.4±3.3) J·g−1, are compared with the assigned value of temperature for the IPTS-68 scale, 1235.08 K, and with a value for enthalpy, 110.75
J·g−1.
Work done at the National Institute of Standards and Technology. Not subject to copyright. 相似文献
4.
34 compounds containing the SO2-N-C-N-moiety are investigated by means of infrared spectroscopy and differential scanning calorimetry to study problems of polymorphic species. There are arguments for different crystalline solids of 16 sulphonyl derivatives. The phenomenon of polymorphism can be discussed both in terms of different hydrogen bonding and conformational effects. Although two tautomers are thinkable for the compounds being investigated the sulphonylimino structure is assumed to yield the most stable state. 相似文献
5.
Several organic compounds like phenanthrene, benzanilide, anisic acid, triphenylene, 2-chloroanthraquinone, hexachlorobenzene, carbazole, 4-iodobenzoic acid, perylene, anthraquinone, as new reference materials for temperature and energy calibration of DTA and DSC apparatuses were studied in the range 300—600 K.
Zusammenfassung Als neue Referenzsubstanzen für Temperatur- und Energiekalibrierung von DTA- und DSC-Geräten wurden im Temperaturbereich 300–600 K einige organische Verbindungen, wie z.B. Phenanthren, Benzanilid, Anissäure, Triphenylen, 2-Chloranthrachinon, Hexachlorbenzol, Karbazol, 4-Jodbenzoesäure, Perylen und Anthrachinon untersucht.相似文献
6.
污水处理工艺对污泥热处理特性的影响 总被引:1,自引:0,他引:1
通过10℃/min时的热重分析,对五种不同性质污泥分别在氮气和氧气气氛下的热解和燃烧特性进行了研究。结果表明,污水处理工艺的“好氧+厌氧”、“厌氧+好氧”过程以及污泥的厌氧消化均使污泥中的有机物结构复杂,导致污泥热解时有机物的分解和析出温度升高,且“好氧+厌氧”过程使污泥中有机物结构更复杂;而对污泥的燃烧过程和燃尽点无影响,但使着火温度升高。利用šatava-šesták 方程对污泥热解、燃烧的反应机理进行了研究。结果表明,五种污泥热解时均呈现为挥发分扩散和随后的化学反应机理函数,而燃烧时则为化学反应和随后的扩散过程。 相似文献
7.
Zaremba T. Dukowicz A. Hehlmann J. Mokrosz W. Kujawska E. 《Journal of Thermal Analysis and Calorimetry》2003,74(2):503-510
DTA, TG and XRD methods were used for the determination of by-product - obtained during flue gas desulfurization by means
of introduction of dehydration - resisting sludge from water decarbonization system. Analysis results enabled the development
and application of sludge utilization technology by means of semi-dry flue gas desulfurization in 'Siersza' power plant.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
The study of 'DSP' binding systems by thermogravimetry and differential thermal analysis 总被引:1,自引:0,他引:1
The so-called DSP (Densified Systems containing homogenously arranged Particles) systems represent a high-performance class
of inorganic binders. The hydration and hardening processes of some DSP systems, based on calcium silicates (C3S and C2S) or Portland cement/clinker with silica fume additions, were assessed, in this paper, using the thermogravimetry (TG) and
differential thermal analysis (DTA). These data permit a qualitative and quantitative study of the formed hydrates as well
as the estimation of hydration process kinetics.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
9.
Ieva Jokubauskaite Kristina Amaleviciute Viia Lepane Alvyra Slepetiene Jonas Slepetys Inga Liaudanskiene 《International journal of environmental analytical chemistry》2015,95(6):508-519
High-performance liquid chromatography (HPLC) with size exclusion (SEC) separation function was used to isolate and examine the molecular mass (MM) distributions and polydispersity of humic substances (HSs) and dissolved organic matter (DOM) from mineral soils and peats. The aim was to improve their detailed characterisation and to inform of their soil carbon (C) sequestration and environmental quality. This is the first study conducted in Lithuania in which HSs and DOM, separated from two soil types, have been used to characterise soil at the molecular level. The HPLC-SEC, as a separation method, was coupled with diode-array detection (DAD), thus enabling the separation of molecular fractions. Results showed that HPLC-SEC can be used to determine the MM of HSs in soil, provided that the relation between retention time and MM is known and a suitable method for fitting the HS peak is available. The UV-spectra analysis showed that DOM has a larger MM (Mw = 2439–3436 Da), which contains more aliphatic C. The HS fraction has a smaller MM (Mw = 2776 Da), with aromatic structures that reflect a higher aromaticity. Separated fractions had characteristic MMs of humic acid (HA) and fulvic acid (FA) and DOM. The HSs separated from peat samples were characterised by higher aromaticity, humification and stability. The HSs extracted from mineral soil samples showed a higher degradability level. The results also show the MM distribution and polydispersity of HS and DOM fractions (Mw/Mn = 1.009–1.252) are relatively homogenous in both soil types. Findings confirm that chromatographic and spectrometric parameters can be used for characterisation of both HSs and DOM, and for detecting changes in organic matter quality. Moreover, they can also be used for a further understanding the C-cycle and could be applied for enhancing soil C-sequestration and informing environmental quality management. 相似文献
10.
M. M. Abou Sekkina 《Journal of Thermal Analysis and Calorimetry》1988,34(3):749-759
A systematic study was made of the relative stability and various phase changes which take place when elemental compound and mechanically mixed semiconductors are heated. These were chalcogens, calcogenides and mixtures of the two. The interest in the present investigation is due to the useful application of the prepared materials in the transistor, radar, rectifier and other electronic industries. Thermogravimetry and differential thermal analysis were carried out in air in the temperature range 20–830°. The results led to the conclusion that the degree of stability of the mechanically mixed semiconducting components is much higher than that of either elemental or compound semiconductors. The results were discussed on the basis of the electronegativity differences and oxygen affinities of the non-metallic components. The thermal stability ranges were evaluated in each case for the materials investigated, for their subsequent physical measurements and their suitability for the production of semiconducting devices. 相似文献
11.
H. B. Hassib Y. M. Issa W. S. Mohamed 《Journal of Thermal Analysis and Calorimetry》2008,92(3):775-782
The electrical and thermal properties of some acetylacetone-(I) and benzoylacetone-(II) arylhydrazone derivatives have been
investigated. The results obtained show semiconductor behavior as evident from the positive temperature coefficient of electrical
conductivity (dG/dT). Values of activation energy (ΔE) have been calculated in each case. The electrical conductivity increases with the introduction of either electron-donating
or electron-withdrawing substituents to the phenyl ring. Differential thermal analysis curves showed sharp well-defined peaks
at the melting point of the investigated compounds. The latent heats of fusion were calculated from these thermograms. 相似文献
12.
Study of initiation reactivity of some plastic explosives by vacuum stability test and non-isothermal differential thermal analysis 总被引:5,自引:0,他引:5
On the basis of measurements of 18 high explosives by means of the Czech Vacuum Stability Test (VST) STABIL, a relationship has been specified between the results of this test and those of Russian manometric method. The said relationship was used to predict the Arrhenius parameters (Ea and log A values) of four plastic explosives based on RDX and one high explosive based on PETN (Semtex). The slopes EaR−1 of Kissinger's equation were specified by means of non-isothermal differential thermal analysis (DTA) and evaluation of the measurement results by means of the Kissinger method. The role played by binders and plasticizers in thermal decomposition of nitramines was pointed out on the basis of relationship between the Ea values obtained from VST and the EaR−1 values obtained from DTA, both for plastic explosives, eight nitramines, Composition B and PETN. The relationships between the EaR−1 values and thermostability threshold was specified for the given group of explosives. The relationship classify some of the studied plastic explosives as belonging to nitramines with steric hindrance in the molecule (CPX, TNAZ and HNIW). The relationship between EaR−1 values and drop energies, Edr, sharply differentiates between plastic explosives and individual nitramines. From the relationship between the Edr and D2 values it was found that the increasing performance of the studied nitramines and plastic explosives is connected with the decrease in their impact sensitivity. Also specified are the approximate linear dependences between the peak temperatures of exothermic decomposition of all the explosives studied and their ignition temperatures, Tig, or critical temperatures, Tc; these dependences were applied to prediction of Tig and Tc of both the studied plastic explosives and some of the nitramines. 相似文献
13.
Basic thermal parameters such as the glass transition and crystallization temperatures of bulk GexSb40−xSe60 (x=15, 20, 25, 27, 32 and 35) glasses have been determined by differential thermal analysis. The observed peculiarity in the variation of the glass transition temperature with the heating rate increase in the narrow range of average coordination number Z=2.65-2.67 has been related to structural and chemical transitions. It has been established that especially the compositions at x=20, 25 and 27 do not crystallize by the applied non-isothermal regime. Identification of the corresponding crystalline phases for the rest samples has been specified. The apparent activation energy of crystallization has values of ∼174 kJ mol−1. 相似文献
14.
Different copper/zirconium-yttrium catalysts have been tested in carbon black oxidation reaction. Supported mainly on differential thermal analysis and temperature programmed reduction, two different mechanisms have been proposed to explain the catalytic results. In the absence of copper, it has been shown that Zr3+ ions and associated anionic vacancies are responsible to the catalytic enhancement observed in the mixed oxides, oxygen species being activated on these sites. Among mixed zirconia-yttria solids, ZrO2-5 mol%Y2O3 is the most active catalyst. Copper impregnation on these oxides leads to the formation of different copper species. Small particles of CuO in low interaction with the support, induce a catalytic improvement due to the highest reducibility of these species. Moreover, in order to be more efficient, CuO species should have some interactions with the support, since impregnated samples are more active than the simple mechanical mixtures. 相似文献
15.
A J M Barros J C O Santos S Prasad V D Leite A G Souza L E B Soledade M S B Duarte V D dos Santos 《Journal of Thermal Analysis and Calorimetry》2006,83(2):291-295
The conventional treatments
of effluents containing heavy metals produce significant quantities of byproducts
with recalcitrant characteristics, making necessary looking after alternative
techniques in order to avoid the production of new contaminated residues.
Sorption process of chromium and zinc in vertical columns loaded with sewage
sludge and organic solid waste has been studied in this work. The data from
the TG curves of the two sorbents presented significant differences when they
were submitted to the metal uptake, being noticed the displacement of the
thermal events towards lower temperatures for both types of sorbents studied.
As it was expected, for both sorbents, an increase in the mass of samples
has been observed at the completion of the thermal tests upon metal uptake.
Therefore, these facts demonstrate that during the biosorption process a physico-chemical
interaction took place between sorbents and metals, as it was evidenced by
the more than 100 K increase in the decomposition temperatures as well as
the variation of the ΔH values of the
samples. 相似文献
16.
André Henrique Rosa Iramaia C. Bellin Danielle Goveia Luciana C. Oliveira Roberto W. Lourenço Peter Burba 《Analytica chimica acta》2006,567(2):152-159
A new procedure was developed in this study, based on a system equipped with a cellulose membrane and a tetraethylenepentamine hexaacetate chelator (MD-TEPHA) for in situ characterization of the lability of metal species in aquatic systems. To this end, the DM-TEPHA system was prepared by adding TEPHA chelator to cellulose bags pre-purified with 1.0 mol L−1 of HCl and NaOH solutions. After the MD-TEPHA system was sealed, it was examined in the laboratory to evaluate the influence of complexation time (0-24 h), pH (3.0, 4.0, 5.0, 6.0 and 7.0), metal ions (Cu, Cd, Fe, Mn and Ni) and concentration of organic matter (15, 30 and 60 mg L−1) on the relative lability of metal species by TEPHA chelator. The results showed that Fe and Cu metals were complexed more slowly by TEPHA chelator in the MD-TEPHA system than were Cd, Ni and Mn in all pH used. It was also found that the pH strongly influences the process of metal complexation by the MD-TEPHA system. At all the pH levels, Cd, Mn and Ni showed greater complexation with TEPHA chelator (recovery of about 95-75%) than did Cu and Fe metals. Time also affects the lability of metal species complexed by aquatic humic substances (AHS); while Cd, Ni and Mn showed a faster kinetics, reaching equilibrium after about 100 min, and Cu and Fe approached equilibrium after 400 min. Increasing the AHS concentration decreases the lability of metal species by shifting the equilibrium to AHS-metal complexes. Our results indicate that the system under study offers an interesting alternative that can be applied to in situ experiments for differentiation of labile and inert metal species in aquatic systems. 相似文献
17.
At room temperature, three of the six polymorphic compounds described are not present in their highest melting-point form, owing to enantiotropy. These three are triphenyltin chloride (3 modifications), 1-(4,4-dimethyl-2-oxo-3-tetrahydrofuryl)thiourea (4 modifications), and 2-aminoethyl diphenylborinate (3 modifications). In the case of 4-amino-1-(2-phenylethyl)-1,2,4-triazoline-5-thione, in addition to the absolutely stable modificationI, a further six unstable crystal forms have been observed. The three modifications of,-dimethyl-[1,1-biphenyl]-4-methanol are also monotropic in character. 2,9-Dimethyl-1,10-phenanthroline, the three polymorphic forms of which are unstable, is a special case, since it absorbs water from the air and changes into a semi-hydrate. 相似文献
18.
Six polymorphic compounds, having between two and five modifications, are described. Enantiotropic modifications were found for three of them: 9-fluorenylmethanol (2 modifications), polyester red A (3 modifications) and polyester red B (3 modifications). There were no indications of enantiotropy in the other three: diphenylcarbamoyl chloride (4 modifications), 4-hydroxyphenylacetic acid (5 modifications) and 2-hydroxy-1-naphthalenecarbaldehyde (5 modifications). 相似文献
19.
Simultaneous
thermogravimetric-mass spectrometric study on the co-combustion of coal and
sewage sludges 总被引:2,自引:0,他引:2
M. Otero M. E. Sánchez A. García A. Morán 《Journal of Thermal Analysis and Calorimetry》2006,86(2):489-495
To combust coal together with a small percentage
(<10%) of sewage sludge may be an option for the management of these wastes.
Combustion of two different sewage sludge, one semianthracite coal and several
sludges-coal blends (containing different dried mass% of each of the two sewage
sludges) were studied by simultaneous TG/MS dynamic runs carried out at 5°C
min–1 in the temperature range 100–800°C.
No interactions have been observed between coal and sludge during the blends
combustion. Neither the combustion process, neither the studied emissions
have changed appreciably for the mass% of sludge in the blends considered
in this work. 相似文献
20.
Su Muzhen Chen Yimin Shi Liping Deng Jun'an Liu Xiaoxin 《Journal of Thermal Analysis and Calorimetry》1992,38(9):2147-2155
DTA was used to study the formation of calcium aluminoferrite from CaO, Al2O3 and Fe2O3 (proportion=2 x 1–x),x=0-3/4) and the effects of C4A3
C11 A7·CacF2, -C2S and MgO on that process. The fusion of CF and the eutectic of CaO-Fe2O3, CA-C12A7, CA-C3A, C12A7-CA-C3A and CA-C2AxF(1–x) will be favourable for the formation. The presence of -C2S and MgO will decrease its formation temperature by an extra eutectic while C4A3
. and C11A7·CaF2 will not.The early heat evolution during the hydration of C2AxF(1–x) were measured by the conduction calorimeter made by ourselves and the products after 1 day hydration were examined by TG and DTA. The results revealed that the peak of heat evolution rise, the amount of the hydrating product iron hydrate gel decreases, CAH10 and C3(A, F)H6 increase with the increase of the value x. The more MgO (up to 5%) soluted in C6AF2, the higher the hydration heat for this solid solution is, when TiO2 soluted in C6AF2 is 2%, the hydration heat for the system reaches the highest.This project is supported by National Natural Science Fundation of China and by the National Science and Technology Developing Fundation in Building Materials Field. 相似文献