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1.
Sibel Kasap Huseyin Tel Sabriye Piskin 《Journal of Radioanalytical and Nuclear Chemistry》2011,289(2):537-544
A spherical polyacrylonitrile–TiO2 composite adsorbent was prepared and its strontium removal potential was investigated. The Langmuir equation fixed well the
equilibrium data. The value of ∆H° = 8.943 kJ/mol and ∆G° = 6.291 kJ/mol at 298 K indicate that the adsorption of strontium onto TiO2/PAN composite adsorbent is an endothermic and non-spontaneous reaction. The kinetic process was described by a pseudo-second-order
rate model very well. 相似文献
2.
Latifa A. Al-Hajji Muhammad A. Hasan Mohamed I. Zaki 《Journal of Thermal Analysis and Calorimetry》2010,100(1):43-49
The formation of Barium monotungstate (BaWO4) particles in equimolar powder mixtures of BaCO3 and WO3 was examined under isothermal and non-isothermal conditions upon heating in air at 25–1200 °C, using thermogravimetry. Concurrence
of the observed mass loss (due to the release of CO2) to the occurrence of the formation reaction was evidenced. Accordingly, the extent of reaction (x) was determined as a function of time (t) or temperature (T). The x–t and x–T data thus obtained were processed using well established mathematical apparatus and methods, in order to characterize nature
of reaction rate-determining step, and derive isothermal and non-isothermal kinetic parameters. Moreover, the reaction mixture
quenched at various temperatures (600–1,000 °C) in the reaction course was analyzed by various spectroscopic and microscopic
techniques, for material characterization. The results obtained indicated that the reaction rate may be controlled by unidirectional
diffusion of WO3 species across the product layer (BaWO4), which was implied to form on the barium carbonate particles. The isothermally determined activation energy (118–125 kJ/mol)
was found to be more credible than that (245 kJ/mol) determined non-isothermally. 相似文献
3.
Tatiana Nedoseykina Pavel Plyusnin Yuri Shubin Sergey Korenev 《Journal of Thermal Analysis and Calorimetry》2010,102(2):703-708
Thermolysis of double complex salt [Pd(NH3)4][AuCl4]2 has been studied in helium atmosphere from ambient to 350 °C. The XAFS of Pd K and Au L3 edges and thermogravimetry measurements have been carried out to characterize the intermediates and the final product. In
the temperature range 115–160 °C the complex is decomposed to form Pd(NH3)2Cl2 and AuCl4−x
N
x
species with x ranging from 2 to 3. Subsequent heating of the intermediate up to 300 °C leads to the total loss of NH3. The Au–Cl and Au–Au bonds form the local environment of Au at the stage of decomposition while only four chlorine atoms
are around Pd. At the temperature of 330 °C the Au and Pd nanoparticles as well as residues of palladium chloride are detected.
The final product consists of separated Au and Pd nanoparticles. 相似文献
4.
Mrinal Khokhani Ramdas B. Khomane Bhaskar D. Kulkarni 《Journal of Sol-Gel Science and Technology》2012,61(2):316-320
Nano squares of sodium-doped lithium zirconate have been synthesized by a simple citrate based sol–gel method at room temperature
in the presence of cetyl trimethylammonium bromide (CTAB) as a surfactant. The structural and morphological properties were
investigated by X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) respectively. XRD analysis of sample calcined
at 900 °C for 4 h shows the formation of monoclinic lithium zirconate phase. The TEM shows the interesting morphology of formation
of nano squares of sodium doped lithium zirconate sample. The carbon dioxide sorption capacity was carried out by TGA analysis
at different high temperatures. It is observed that the sample shows ~20 wt% carbon dioxide sorption at higher temperature
(650 °C) within 20 min which are better than the known reports. 相似文献
5.
Summary Hydrous zirconium dioxide was prepared to study the sorption behavior and the removal of strontium from radioactive waste
solutions. The hydrous zirconium dioxide were identified and characterized. The parameters affecting the strontium adsorption
were investigated. Sorption data have been interpreted in terms of Langmuir equations. Thermodynamic parameters for the sorption
system have been determined at 303, 313, 323 and 333 K temperatures. The values ofDH°=102.30 kJ/mol andDG°=-26.03 kJ/mol at 313 K prove that the sorption of strontium on hydrous zirconium oxide is an endothermic and a spontaneous
process. 相似文献
6.
Cornelia Marinescu Ancuta Sofronia Cristina Rusti Roxana Piticescu Viorel Badilita Eugeniu Vasile Radu Baies Speranta Tanasescu 《Journal of Thermal Analysis and Calorimetry》2011,103(1):49-57
The aim of the article is to investigate the influence of particle size on titanium dioxide phase transformations. Nanocrystalline
titanium dioxide powder was obtained through a hydrothermal procedure in an aqueous media at high pressure (in the range 25–100 atm)
and low temperature (≤200 °C). The as-prepared samples were characterized with respect to their composition by ICP (inductive
coupled plasma), structure and morphology by XRD (X-ray diffraction), and TEM (transmission electron microscopy), thermal
behavior by TG (thermogravimetry) coupled with DSC (differential scanning calorimetry). Thermal behavior of nanostructured
TiO2 was compared with three commercial TiO2 samples. The sequence of brookite–anatase–rutile phase transformation in TiO2 samples was investigated. The heat capacity of anatase and rutile in a large temperature range are reported. 相似文献
7.
D. M. Babanly G. M. Guseinov M. B. Babanly F. M. Sadygov 《Russian Journal of Inorganic Chemistry》2012,57(1):90-99
Phase equilibria in the Tl-TlI-S composition region of the Tl-S-I system were studied by differential thermal analysis, x-ray
powder diffraction, and measurements of the microhardness and the emf of concentration circuits relative to a thallium electrode.
A series of polythermal sections, an isothermal section at 300 K, and a projection of the liquidus surface were constructed.
Primary crystallization regions of six phases, including the ternary compounds Tl6SI4 and Tl3SI, were outlined, and the types and coordinates of non- and monovariant equilibria were determined. It was shown that the
ternary compound Tl6SI4 forms tie lines with Tl, TlI, Tl2S, Tl4S3, and TlS in the subsolidus region and that the homogeneity region of Tl6SI4 below 400 K does not exceed 1 mol %. From the emf measurement data, the standard thermodynamic functions of formation and
standard entropy of the compound Tl6SI4 were calculated: G
f,2980 = −601.7 ± 2.5 kJ/mol, ΔH
f,2980= −595.1 ± 4.0 kJ/mol, and S
2980 = 672 ± 10 J/(mol K). 相似文献
8.
Sorption equilibrium of methanol on new composite sorbents “CaCl<Subscript>2</Subscript>/silica gel”
Yuri I. Aristov Larissa G. Gordeeva Yuri D. Pankratiev Ludmila M. Plyasova I. V. Bikova Angelo Freni Giovanni Restuccia 《Adsorption》2007,13(2):121-127
This paper presents experimental data on methanol sorption on new composite sorbents which consist of mesoporous silica gels
and calcium chloride confined to their pores. Sorption isobars and XRD analysis showed the formation of a solid crystalline
solvate CaCl2⋅2MeOH at low methanol uptake, while at higher uptake the formation of the CaCl2–methanol solution occurred. The solution confined to the silica pores showed the sorption properties similar to those of
the CaCl2–methanol bulk solution. Calorimetric and isosteric analyses showed that the heat of methanol sorption depends on the methanol
uptake, ranging from 38±2 kJ/mol for the solution to 81±4 kJ/mol for the solid crystalline phase CaCl2⋅2MeOH. The above mentioned characterizations allowed the evaluation of the methanol sorption and the energy storage capacities,
clearly showing that the optimal applications of these new composite sorbents are the methanol removal from gaseous mixtures,
heat storage and sorption cooling driven by low temperature heat. 相似文献
9.
Daniela de Araújo Viana Carolina de Albuquerque Lima Rejane Pereira Neves Cristina Souza Mota Keila Aparecida Moreira José Luiz de Lima-Filho Maria Taciana Holanda Cavalcanti Attilio Converti Ana Lúcia Figueiredo Porto 《Applied biochemistry and biotechnology》2010,162(3):830-842
Cow raw milk from dairy cooperatives was examined for its microbial composition. Among the isolates identified, 17.6% were
yeasts. The most frequent genus was Candida, although members belonging to the genera Brettanomyces, Dekkera, and Geotricum were also identified. Although qualitative and quantitative tests for extracellular proteolytic activity were positive for
all the species isolated, Candida buinensis showed the highest response (23.5 U/mg); therefore, it was selected for subsequent investigation. The results of fermentations
carried out at variable temperature, pH, and soybean flour concentration, according to a 23 full factorial design, demonstrated that this yeast ensured the highest production of extracellular proteases (573 U/mL)
when cultivated at 35 °C, pH 6.5, and using soybean flour concentrations in the range 0.1–0.5% (w/v). The cell-free supernatants showed the highest activity at 25 °C and pH 7.0, and satisfactory stability in the ranges 25–30 °C
and pH 7–9. The first-order rate constants of protease inactivation in the cell-free supernatants were calculated at different
temperatures from semi-log plots of the residual activity versus time and then used in Arrhenius and Eyring plots to estimate
the main thermodynamic parameters of thermoinactivation (E* = 40.0 kJ/mol; ΔH* = 37.3 kJ/mol; ΔS* = −197.5 J/mol K; ΔG* = 101 kJ/mol). 相似文献
10.
Abdelhakim Kadous Mohamed Amine Didi Didier Villemin 《Journal of Radioanalytical and Nuclear Chemistry》2011,288(2):553-561
Removal of uranium(VI) ions from acetate medium in aqueous solution was investigated using Lewatit TP260 (weakly acidic, macroporous-type
ion exchange resin with chelating aminomethylphosphonic functional groups) in batch system. The parameters that affect the
uranium(VI) sorption, such as contact time, solution pH, initial uranium(VI) concentration, adsorbent dose and temperature
have been investigated. Results have been analyzed by Langmuir and Freundlich isotherm; the former was more suitable to describe
the sorption process. The moving boundary particle diffusion model only fits the initial metal adsorption on the resin. The
rate constant for the uranium sorption by Lewatit TP260 was 0.441 min−1 from the first order rate equation. The total sorption capacity was found to be 58.33 mg g−1 under optimum experimental conditions. Thermodynamic parameters (ΔH = 61.74 kJ/mol; ΔS = 215.3 J/mol K; ΔG = −2.856 kJ/mol) showed the adsorption of an endothermic process and spontaneous nature, respectively. 相似文献
11.
Yttrium
orthoborate crystallizes in the vaterite-type structure and has two polymorphous
forms, viz. a low- und a high temperature one. DTA measurements of YBO3
confirmed a reversible phase transition with a large thermal hysteresis. The
phase transition has been accurately characterized by the application of different
heating and cooling rates (β). Consequently, the extrapolation of the
experimental data to zero β yields the transition points at 986.9°C
for the heating up and at 596.5°C for the cooling down cycle. These values
correspond to samples just after treatment at 1350°C. For samples with
a different ‘thermal history’ other phase transition temperatures
are observed, (e.g. after having performed several heating and cooling cycles).
The linear relationship between the associated DTA signal ΔT=T
onset–T
offset and the square root
of the heating rate β was confirmed, but the relation between T
onset and square root of β
is not found here.
From the empirical data a good linear fitting
between T
onset and
ln(β+1) can be derived.
From the kinetic analysis (Kissinger
method) of the phase transformation of YBO3 an apparent
activation energy of about 1386 kJ mol–1
for heating and of about 568 kJ mol–1 for
cooling can be determined 相似文献
12.
Yu. I. Gnatyuk V. I. Yatskiv N. P. Smirnova V. M. Granchak A. M. Eremenko 《Theoretical and Experimental Chemistry》2005,41(6):371-376
We have used the sol-gel template synthesis method to obtain mesoporous zirconium-containing titanium dioxide films and have
studied their structural and sorption characteristics, surface acid function, and photocatalytic activity during gas-phase
oxidation of aliphatic alcohols. We have shown that the zirconium content changes the acidity and specific surface area of
the films, determining the rate at which the studied processes occur and the relative yield of reaction products.
__________
Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 41, No. 6, pp. 354–359, November–December, 2005. 相似文献
13.
The phase transition at T
p (~109 °C) of RbH2PO4 and its composite with SiO2 has been investigated by thermal analysis here. In the case of neat RbH2PO4, there is a linear relationship between endothermic peak temperature (T
m) and square root of heating rate (Φ
1/2), from which the onset temperature of phase transition can be determined. Besides, Kissinger method and another calculation
method were employed to obtain the activation energy of phase transition. The detailed deduction process was presented in
this paper, and the estimated activation energies are E
1 ≈ 126.3 kJ/mol and E
2 ≈ 129.2 kJ/mol, respectively. On the other hand, the heterogeneous doping of RbH2PO4 with SiO2 as dopant facilitates its proton conduction and leads to the disappearance of jump in conductivity at T
p. The heats of transition in the composites decrease gradually with increasing the molar fraction of SiO2 additives. In the cooling process, a new and broad exothermic peak appeared between ~95 and ~110 °C, and its intensity also
changes with the SiO2 amount. These phenomena might be related to the formation of amorphous phase of RbH2PO4 on the surface of SiO2 particles due to the strong interface interaction. 相似文献
14.
In this work, Na-montmorillonite was used as a novel adsorbent for the sorption of Ni(II) from aqueous solutions. The sorption
and desorption of Ni(II) on Na-montmorillonite was investigated as the function of pH, ionic strength, Ni(II) concentrations
and temperature. The results indicated that the sorption of Ni(II) on Na-montmorillonite was strongly dependent on pH, ionic
strength and temperature. The sorption of Ni(II) increases slowly from 22.1 to 51.4% at pH range 2–6.5, abruptly at pH 6.5–9,
and at last maintains high level with increasing pH at pH > 9 in 0.1 mol/L NaNO3 solutions. The Ni(II) kinetic sorption on Na-montmorillonite was fitted by the pseudo-second-order model better than by the
pseudo-first-order model and the experimental data implies that Ni(II) sorption on montmorillonite were mainly controlled
by the film diffusion mechanism. The Langmuir, Freundlich and D–R models were used to simulate the sorption data at three
different temperatures (298.15, 318.15 and 338.15 K) and the results indicated that Langmuir model simulates the experimental
data better than Freundlich and D–R models. The sorption–desorption isotherm of Ni(II) on montmorillonite suggested that the
sorption is irreversible. The irreversible sorption of Ni(II) on montmorillonite indicates that montmorillonite can be used
to pre-concentration and solidification of Ni(II) from large volumes of solution and to storage Ni(II) ions stably. 相似文献
15.
YunHai Wu Yue Hu ZhengWei Xie ShiXun Feng Bin Li XianMiao Mi 《Applied biochemistry and biotechnology》2011,163(7):882-894
The use of cheap, high-efficiency, and ecofriendly adsorbent has been studied as an alternative way for the removal of dyes
from wastewater. This paper investigated the use of waste brewery’s yeast for the removal of acid orange 7 from aqueous solution.
The optimum removal of acid orange 7 was found to be 3.561 mg/g at pH 2.0, 10 mg/L initial concentration and 303 K. The kinetic
studies indicated that the biosorption process of acid orange 7 agreed well with the pseudo-second-order model. The external
diffusion is the rate-controlling step of the initial fast adsorption (<20 min) and then the intraparticle diffusion dominated
the mass transfer process. Langmuir, Freundlich, and Dubinin–Radushkevich models were applied to describe the biosorption
isotherm of acid orange 7 by waste brewery’s yeast. Langmuir isotherm model fits the equilibrium data, at all the studied
temperatures, better than the other isotherm models which indicates monolayer dye biosorption process. The highest monolayer
biosorption capacity was found to be 2.27 × 10−3 mol/g at 303 K. The calculated thermodynamic parameters (ΔG, ΔS, ΔH) showed the biosorption process to be spontaneous and exothermic in nature. Amine or amino, amide, carboxyl, phosphate groups
are responsible for the dyes biosorption based on the result of Fourier transform infrared analysis. 相似文献
16.
Lei Zhang Hongmei Li Xueyan Liu Pingli Kang 《Russian Journal of Inorganic Chemistry》2012,57(4):622-628
Titanium dioxide nanoparticles were employed for the sorption of Ge(IV) ions from aqueous solution. The process was studied
in detail by varying the sorption time, pH, and temperature. The sorption process was found to be fast, equilibrium was reached
within 3 min. A maximum sorption could be achieved from solution when the pH ranges between 4.0 and 11.0. Sorbed Ge(IV) ions
can be completely desorbed with 2 mL of 0.3 mol L−1 K3PO4-1.0 mol L−1 H2SO4 mixture solution. The kinetic experimental data properly correlate with the second-order kinetic model (k
2 = 0.88 g mg−1 min−1 (25°C)), Reichenberg equation and Morris-Weber model. The estimated E
a
for Ge(IV) adsorption on nano-TiO2 was 19.66 kJ mol−1. The overall rate process appears to be influenced by intra-particle diffusion. The sorption data could be well interpreted
with the Langmuir and Dubinin-Radushkevich (D-R) type sorption isotherms. The D-R parameters were calculated to be K = −0.00321 mol2 kJ−2, q
m
= 0.59 mmol g−1 and E = 12.48 kJ mol−1 at room temperature. Furthermore, the thermodynamic parameters were also determined, and the ΔH
0 and ΔG
0 values indicated a spontaneous exothermic behavior. 相似文献
17.
Andres Trikkel Merli Keelmann Tiit Kaljuvee Rein Kuusik 《Journal of Thermal Analysis and Calorimetry》2010,99(3):763-769
In the present research, CO2 and SO2 binding ability of different oil shale ashes and the effect of pre-treatment (grinding, preceding calcination) of these ashes
on their binding properties and kinetics was studied using thermogravimetric, SEM, X-ray, and energy dispersive X-ray analysis
methods. It was shown that at 700 °C, 0.03–0.28 mmol of CO2 or 0.16–0.47 mmol of SO2 was bound by 100 mg of ash in 30 min. Pre-treatment conditions influenced remarkably binding parameters. Grinding decreased
CO2 binding capacities, but enhanced SO2 binding in the case of fluidized bed ashes. Grinding of pulverized firing ashes increased binding parameters with both gases.
Calcination at higher temperatures decreased binding parameters of both types of ashes with both gases studied. Clarification
of this phenomenon was given. Kinetic analysis of the binding process was carried out, mechanism of the reactions and respective
kinetic constants were determined. It was shown that the binding process with both gases was controlled by diffusion. Activation
energies in the temperature interval of 500–700 °C for CO2 binding with circulating fluidized bed combustion ashes were in the range of 48–82 kJ mol−1, for SO2 binding 43–107 kJ mol−1. The effect of pre-treatment on the kinetic parameters was estimated. 相似文献
18.
Efficient uranium(VI) biosorption on grapefruit peel: kinetic study and thermodynamic parameters 总被引:3,自引:0,他引:3
The uranium(VI) biosorption by grapefruit peel was studied from aqueous solutions. Batch experiments was conducted to evaluate
the effect of contact time, initial uranium(VI) concentration, initial pH, adsorbent dose, salt concentration and temperature.
The equilibrium process was well described by the Langmuir, Redlich–Peterson and Koble–Corrigan isotherm models, with maximum
sorption capacity of 140.79 mg g−1 at 298 K. The pseudo second order model and Elovish model adequately describe the kinetic data in comparison to the pseudo
first order model and the process involving rate-controlling step is much complex involving both boundary layer and intra-particle
diffusion processes. The effective diffusion parameter D
i and D
f values were estimated at different initial concentration and the average values were determined to be 1.167 × 10−7 and 4.078 × 10−8 cm2 s−1. Thermodynamic parameters showed that the biosorption of uranium(VI) onto grapefruit peel biomass was feasible, spontaneous
and endothermic under studied conditions. The physical and chemical properties of the adsorbent were determined by SEM, TG-DSC,
XRD and elemental analysis and the nature of biomass–uranium (VI) interactions was evaluated by FTIR analysis, which showed
the participation of COOH, OH and NH2 groups in the biosorption process. Adsorbents could be regenerated using 0.05 mol L−1 HCl solution at least three cycles, with up to 80% recovery. Thus, the biomass used in this work proved to be effective materials
for the treatment of uranium (VI) bearing aqueous solutions. 相似文献
19.
The solubility of industrially produced titanium dioxide nanoparticles has been studied in aqueous sodium chloride media in
the pH range 1 to 13 at 25 °C by using adsorptive stripping voltammetry (AdSV). Kinetic dissolution curves have been obtained
as well as long-term solubilities that provide an approximation of the equilibrium solubilities. The titania nanoparticles
used in the dissolution experiments have been characterized by nitrogen sorption measurements, XRD and colloid titration.
The equilibrium solubilities and titanium(IV) speciation and their dependences on pH have been modelled by assuming the formation
of the mononuclear titanium hydroxo complexes [Ti(OH)
n
](4−n)+ (n=2 to 5) to be the only titanium species present. The solubility product of titanium dioxide and equilibrium constants for
titanium(IV) hydrolysis, calculated from the AdSV solubility data, are presented. 相似文献
20.
Shih-Yuan Lin Ying-Chung Chen Chih-Ming Wang Chan-Chih Liu 《Journal of Solid State Electrochemistry》2008,12(11):1481-1486
Electrochromic titanium oxide (TiO2) films were deposited on ITO/glass substrates by chemical solution deposition (CSD). The stock solutions were spin-coated
onto substrates and then heated at various temperatures (200–500 °C) in various oxygen concentrations (0–80%) for 10 min.
The effects of the processing parameters on the electrochromic properties of TiO2 films were investigated. X-ray diffraction measurements demonstrated that the amorphous TiO2 films were crystallized to form anatase films above 400 °C. The electrochromic properties and transmittance of TiO2 films were measured in 1 M LiClO4–propylene carbonate (PC) non-aqueous electrolyte. An amorphous 350 nm-thick TiO2 film that was heated at 300°C in 60% ambient oxygen exhibited the maximum transmittance variation (ΔT%), 14.2%, between the bleached state and the colored state, with a ΔOD of 0.087, Q of 10.9 mC/cm2, η of 7.98 cm2/C and x in Li
x
ClO4 of 0.076 at a wavelength (λ) of 550 nm. 相似文献