Kinetics of the thermal dehydration of variscite and specific surface area of the solid decomposition products

1973 ◽  
Vol 5 (2-3) ◽  
pp. 319-328 ◽  
Author(s):  
A. Mata Arjona ◽  
M. A. Alario Franco
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Thermal Dehydration ◽  
Decomposition Products ◽  
Solid Decomposition ◽  
Kinetics Of

Study on the kinetics of process for obtaining cobalt nanopowder by hydrogen reduction under isothermal conditions

2021 ◽  
Vol 1 (1) ◽  
pp. 49-56
Author(s):  
Hieр Nguyen Tien
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Hydrogen Reduction ◽  
Average Particle Size ◽  
Chemical Deposition ◽  
Average Particle ◽  
Isothermal Conditions ◽  
Electron Microscopes ◽  
Kinetics Of

The kinetics of metallic cobalt nanopowder synthesizing by hydrogen reduction from Co(OH)2 nanopowder under isothermal conditions were studied. Co(OH)2 nanopowder was prepared in advance by chemical deposition from aqueous solutions of Co(NO3)2 cobalt nitrate (10 wt.%) and NaOH alkali (10 wt.%) at room temperature, pH = 9 under continuous stirring. The hydrogen reduction of Co(OH)2 nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 270 to 310 °C. The crystal structure and composition of powders was studied by X-ray phase analysis. The specific surface area of samples was measured using the BET method by low-temperature nitrogen adsorption. The average particle size of powders was determined by the measured specific surface area. Particles size characteristics and morphology were investigated by transmission and scanning electron microscopes. Kinetic parameters of Co(OH)2 hydrogen reduction under isothermal conditions were calculated using the Gray–Weddington model and Arrhenius equation. It was found that the rate constant of reduction at t = 310 °C is approximately 1.93 times higher than at 270 °C, so the process accelerates by 1.58 times for 40 min of reduction. The activation energy of cobalt nanopowder synthesizing from Co(OH)2 by hydrogen reduction is ~40 kJ/mol, which indicates a mixed reaction mode. It was shown that cobalt nanoparticles obtained by the hydrogen reduction of its hydroxide at 280 °C are aggregates of equiaxed particles up to 100 nm in size where individual particles are connected to several neighboring particles by contact isthmuses.

scholarly journals Adsorption and Photodegradation of Cationic and Anionic Dyes by TiO2-Chitosan Nanocomposite

2019 ◽  
Vol 19 (2) ◽  
pp. 441
Author(s):  
Imelda Fajriati ◽  
Mudasir Mudasir ◽  
Endang Tri Wahyuni
Keyword(s):  
Specific Surface ◽  
Adsorption Capacity ◽  
Surface Area ◽  
Specific Surface Area ◽  
Maximum Adsorption Capacity ◽  
Anionic Dyes ◽  
Anionic Dye ◽  
Reaction Constant ◽  
Kinetics Of

The adsorption and photodegradation of cationic and anionic dyes by TiO2-chitosan nanocomposites have been studied. This study investigated the specific surface area, pores volume, pores size of TiO2-Chitosan nanocomposite, and determination kinetics of the reaction on the adsorption and photodegradation process. The methods were carried out by mixing TiO2-nanocomposite into cationic and anionic dyes in various contact times and initial dye concentrations. The results showed that nanocomposite adsorption capacity increased with an increase in the amount of chitosan (TiO2/Chit 0.13) even though the specific surface area (SBET) was reduced. The results indicated that the adsorption on nanocomposite was influenced by the amount of -NH2 and -OH on the chitosan surface. The maximum adsorption capacity (qm) and the observed reaction constant (kObs) for MO were also known to be higher than MB, which means that the TiO2-chitosan nanocomposites could remove anionic dye more than cationic one.

POTASSIUM CARBONATE-TREATED PALM KERNEL SHELL ADSORBENT FOR CONGO RED REMOVAL FROM WATER

2015 ◽  
Vol 75 (1) ◽  
Author(s):  
Lee Lin Zhi ◽  
Muhammad Abbas Ahmad Zaini
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Potassium Carbonate ◽  
Congo Red ◽  
Palm Kernel ◽  
Surface Functional Groups ◽  
Palm Kernel Shell ◽  
Pseudo Second Order ◽  
Kinetics Of

This work was aimed to evaluate the adsorptive characteristics of potassium carbonate-treated palm kernel shell adsorbent for the removal of congo red from water. The adsorbent was characterized according to the specific surface area, surface morphology and surface functional groups. The bottle-point technique was employed to investigate the equilibrium uptake and the adsorption kinetics of congo red, and the removal mechanisms were proposed from the widely used isotherm and kinetics models. Results show that the specific surface area of adsorbent increased after the treatment rendering the maximum congo red uptake of 8.0 mg/g. The removal of congo red obeyed Langmuir isotherm and pseudo-second-order kinetics model suggesting the chemically-attributed homogeneous adsorption. Regeneration of congo red-loaded adsorbent by irradiated water showed a better regeneration efficiency of 82%. Palm kernel shell is a promising adsorbent candidate for congo red removal from water.

Preparation and Hydration Kinetics of Pure CaAl2O4

1991 ◽  
Vol 245 ◽  
Author(s):  
M. A. Gulgun ◽  
O. O. Popoola ◽  
I. Nettleship ◽  
W. M. Kriven ◽  
J. F. Young
Keyword(s):  
Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Single Phase ◽  
Hydration Kinetics ◽  
Phase Pure ◽  
Microscopy Techniques ◽  
Kinetics Of

ABSTRACTSingle phase, pure monocalcium aluminate (CaAl2O4) powders are chemically synthesized at temperatures as low as 900°C. The powders have a specific surface area of approximately 10 m2/g. The hydration kinetics of CaAl2O4 and the morphology of the hydrates are analyzed using electron microscopy techniques

scholarly journals New Concept for the Study of the Fluid Dynamics of Lithium Extraction Using Calix[4]arene Derivatives in T-Type Microreactor Systems

Separations ◽  
2021 ◽  
Vol 8 (5) ◽  
pp. 70
Author(s):  
Yehezkiel Steven Kurniawan ◽  
Ramachandra Rao Sathuluri ◽  
Keisuke Ohto ◽  
Wataru Iwasaki ◽  
Hidetaka Kawakita ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Average Length ◽  
Economic Value ◽  
Extraction Rate ◽  
Slow Kinetics ◽  
Kinetics Of ◽  
Area And Volume

Lithium extraction remains a challenge in the hydrometallurgy process due to its economic value and maldistribution sources. Employing calix[4]arene derivatives in solvent extraction techniques results in high selectivity and extraction capability, but a slow extraction rate. The slow kinetics of batch-wise extraction can be drastically accelerated by using a T-type microreactor system. Therefore, a combination of calix[4]arene and a microreactor system serves as an ideal platform for efficient lithium extraction. In this work, the fluid dynamics of lithium extraction using a monoacetic acid calix[4]arene derivative in a T-type microreactor system were studied. Increasing the O/A ratio increases the average length, surface area, and volume of the organic droplets, but decreases the specific surface area. In contrast, increasing the Reynolds number decreases the average length, surface area, and volume of the organic droplets, but increases the specific surface area. It was found that shorter diffusion distance, larger specific surface area, and faster vortex velocity were the factors that play the most pivotal roles in achieving great extraction rate enhancement in T-type microreactor systems compared to batch-wise systems. These findings represent an important new concept in the study of the fluid dynamics of lithium extraction using monoacetic acid calix[4]arene derivatives in T-type microreactor systems.

scholarly journals Investigation of sintering kinetics of ZnO by observing reduction of the specific surface area

2007 ◽  
Vol 39 (3) ◽  
pp. 259-265 ◽  
Author(s):  
S. Stevanovic ◽  
V. Zeljkovic ◽  
N. Obradovic ◽  
N. Labus
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Arrhenius Equation ◽  
Sintering Process ◽  
Sintering Time ◽  
Activation Energy Of Sintering ◽  
Zno Powder ◽  
Parameter Values ◽  
Kinetics Of

Reduction of the specific surface area of porous ZnO during the sintering process was studied. ZnO powder was sintered at temperatures from 673 K to 1173 K. The decrease in the specific surface area was observed as a function of temperature and sintering time. Two different models were involved in order to define the appropriate parameters. The Arrhenius equation was used to give information on the activation energy of sintering. The LSE method was applied for determining optimum parameter values.

scholarly journals Kinetics of specific surface area change using the Boltzmann model

2009 ◽  
Vol 41 (3) ◽  
pp. 267-274 ◽  
Author(s):  
N. Djordjevic ◽  
S. Martinovic ◽  
M. Vlahovic ◽  
P. Jovanic ◽  
V. Vidojkovic ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mechanochemical Activation ◽  
Thermal Analyses ◽  
Formation Temperature ◽  
Surface Areas ◽  
Surface Area Change ◽  
Boltzmann Model ◽  
Kinetics Of

During sintering of the 2MgO-2Al2O3-5SiO2 system, cordierite, an attractive ceramic material because of its properties, is obtained. Effects of mechanochemical activation of stoichiometric mixtures, performed to investigate possibilities of lowering cordierite formation temperature during sintering, were monitored by thermogravimetric and differential thermal analyses. Specific surface areas of the mechanically activated powder mixtures were determined by the BET method. Kinetics of the specific surface area increase was analyzed using the Boltzmann model. It was confirmed that with activation time increase, temperatures of phase transformations were shifted to lower values and, according to FTIR analysis no significant changes occurred during material aging. According to the obtained results, it may be concluded that since mechanochemical activation has an influence on the treated powder mixture, lowering of the cordierite formation temperature during the sintering process is expected.

scholarly journals Do Adsorbent Pore Size and Specific Surface Area Affect The Kinetics of Methyl Orange Aqueous Phase Adsorption?

2021 ◽  
Author(s):  
KINGSLEY OGEMDI IWUOZOR ◽  
Joshua O. Ighalo ◽  
Ebuka Chizitere Emenike ◽  
Chinenye Adaobi Igwegbe ◽  
Adewale George Adeniyi
Keyword(s):  
Methyl Orange ◽  
Specific Surface ◽  
Pore Size ◽  
Surface Area ◽  
Aqueous Phase ◽  
Specific Surface Area ◽  
Statistical Significance ◽  
Theoretical Perspective ◽  
Phase Interface ◽  
Kinetics Of

Abstract The kinetics of any adsorption reaction gives more information on the rate at which the adsorbate is taken up by the adsorbent, which is responsible for the residence time of an adsorbate uptake at the adsorbent-aqueous phase interface. This study was aimed at determining the effect of pore size as well as specific surface area (SSA) on the kinetics of the uptake of methyl orange (MO). The basis of the analysis was from data on kinetic models sourced from recent literature. ANOVA of the data revealed that statistical significance was achieved for SSA but not for pore size (at a significance level of 0.05). This called for a more theoretical perspective on the research data. The kinetics constant for micropores is far higher than for the two selected regimes of the mesopore. For the SSA, 100–10 m2/g adsorbents had a higher mean k2 value. This suggested that adsorbents in the SSA range had pore sizes that favour rapid uptake. However, further studies will be needed to gain a better understanding of how SSA affects adsorption kinetics. The study also discussed the technical limitations that could arise due to the use of kinetic model linearisation.

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