scholarly journals Reduction and Immobilization of Movable Cu2+ Ions in Soils by Fe78Si9B13 Amorphous Alloy

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 310
Author(s):  
Liefei Pei ◽  
Xiangyun Zhang ◽  
Zizhou Yuan
Keyword(s):  
Activation Energy ◽  
Amorphous Alloy ◽  
Apparent Activation Energy ◽  
Magnetic Separation ◽  
Dynamic Process ◽  
Contaminated Soils ◽  
Iron Hydroxide ◽  
Reaction Rate Constant ◽  
Reaction Products ◽  
Soil System

The Fe-based amorphous alloy (Fe78Si9B13AP) is applied to the remediation of copper contaminated soil for the first time. The dynamic process of conversion of movable Cu to immobilized forms in the soil system is analyzed. In addition, the dynamic process of form transformation of Cu2+ ions in the soil system is analyzed. The morphology and phase composition of the reaction products are characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Finally, the feasibility of recovering residual stabilizer particles and attached immobilized copper by the magnetic separation process is discussed. The results show that the apparent reaction rate constant of Fe79Si9B13AP with Cu2+ ions is higher than that of zero valent iron (ZVI) at all the experimental temperatures. According to the Arrhenius formula, the apparent activation energy of the reaction of Fe78Si9B13AP and ZVI with Cu2+ ions is 13.24 and 19.02 kJ/mol, respectively, which is controlled by the diffusion process. The lower apparent activation energy is one of the important reasons for the high reaction activity of Fe78Si9B13AP. After 7 days of reaction, a continuous extraction of the experimental soil shows that the main form of copper in the immobilized soil is Cu and copper combined with iron (hydroxide) oxide, and there is almost no soluble copper with a strong mobility, which effectively reduced the bioavailability of copper in the soil. The magnetic separation results of the treated soil show that the recovery rates of immobilized copper in Fe78Si9B13AP and soil are 47.23% and 21.56%, respectively, which reduced the content of iron and copper in the soil to a certain extent. The above experimental results show that Fe78Si9B13AP is a promising new material for the remediation of heavy metal contaminated soils, and provides more new references for the application of amorphous alloys in the field of remediation of water and soil contaminated by heavy metals and organic matter.

Reduction Kinetics of Bayan Obo Coexisted Iron and Niobium Ore by Carbon-Bearing Pellet

2011 ◽  
Vol 418-420 ◽  
pp. 346-352 ◽  
Author(s):  
Fu Shun Zhang ◽  
Zeng Wu Zhao ◽  
Yan Li ◽  
Nai Xiang Feng
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Reaction Rate ◽  
Mass Loss Rate ◽  
Reduction Process ◽  
Inert Atmosphere ◽  
Reaction Rate Constant ◽  
Carbon Gasification ◽  
Reaction Rate Constants ◽  
Two Stages

The mass loss rate of carbon-bearing pellet of coexisted iron and niobium ore during reduction process was investigated between 900 and 1050°C in inert atmosphere. The reduction mechanism was studied by analyzing reaction rate constant, apparent activation energy，and the controlling step. The results show that temperature has the significant effect on the reduction of carbon-bearing pellet. The reduction processes include the faster reaction stage and the slower reduction stage, and respective reaction rate constants in two stages are k1=exp (21.025-40484/(RT)) and k2= exp (21.060-42516/(RT))，while respective apparent activation energy are 337 and 353 KJ/mol. Both steps are controlled by carbon gasification.

scholarly journals The Hydrothermal Stability and the Properties of Non- and Strongly-Interacting Rh Species over Rh/γ, θ-Al2O3 Catalysts

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 99
Author(s):  
Guanghao Cheng ◽  
Gurong Shen ◽  
Jun Wang ◽  
Yunhao Wang ◽  
Weibo Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Aging Time ◽  
Reaction Path ◽  
Aging Treatment ◽  
Hydrothermal Stability ◽  
Hydrothermal Aging ◽  
Strongly Interacting

The present work reports the effects of γ-, θ-phase of alumina on the hydrothermal stability and the properties of non- and strongly-interacting Rh species of the Rh/Al2O3 catalysts. Comparing to γ-Al2O3, θ-Al2O3 can not only reduce the amount of occluded Rh but also better stabilize Rh during hydrothermal aging treatment. When the aging time was prolonged to 70 h, all the non-interacting Rh was transformed into strongly-interacting Rh and occluded Rh. The XPS results indicated that non- and strongly-interacting Rh might exist in the form of Rh/Rh3+ and Rh4+, respectively. CO-NO reaction was chosen as a probe reaction to research more information about non- and strongly-interacting Rh. The two Rh species had similar apparent activation energy (Eapp) of 170 kJ/mol, which indicated that non- and strongly-interacting Rh follow the same reaction path. The non-interacting Rh was removed from aged samples by the acid-treated method, and obtained results showed that only 2.5% and 4.0% non-interacting Rh was maintained in aged Rh/γ-Al2O3 and Rh/θ-Al2O3.

The activation energy U(T,B) in high temperature superconductor

2020 ◽  
Vol 92 (2) ◽  
pp. 20601
Author(s):  
Abdelaziz Labrag ◽  
Mustapha Bghour ◽  
Ahmed Abou El Hassan ◽  
Habiba El Hamidi ◽  
Ahmed Taoufik ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Activation Energy ◽  
Phase Diagram ◽  
High Temperature ◽  
Apparent Activation Energy ◽  
High Temperature Superconductor ◽  
Flux Flow ◽  
Resistivity Measurements ◽  
Vortex Phase ◽  
The Magnetic Field

It is reported in this paper on the thermally assisted flux flow in epitaxial YBa2Cu3O7-δ deposited by Laser ablation method on the SrTiO3 substrate. The resistivity measurements ρ (T, B) of the sample under various values of the magnetic field up to 14T in directions B∥ab-plane and B∥c-axis with a dc weak transport current density were investigated in order to determine the activation energy and then understand the vortex dynamic phenomena and therefore deduce the vortex phase diagram of this material. The apparent activation energy U0 (B) calculated using an Arrhenius relation. The measured results of the resistivity were then adjusted to the modified thermally assisted flux flow model in order to account for the temperature-field dependence of the activation energy U (T, B). The obtained values from the thermally assisted activation energy, exhibit a behavior similar to the one showed with the Arrhenius model, albeit larger than the apparent activation energy with ∼1.5 order on magnitude for both cases of the magnetic field directions. The vortex glass model was also used to obtain the vortex-glass transition temperature from the linear fitting of [d ln ρ/dT ] −1 plots. In the course of this work thanks to the resistivity measurements the upper critical magnetic field Hc2 (T), the irreversibility line Hirr (T) and the crossover field HCrossOver (T) were located. These three parameters allowed us to establish a phase diagram of the studied material where limits of each vortex phase are sketched in order to optimize its applicability as a practical high temperature superconductor used for diverse purposes.

scholarly journals Effect of CaO on catalytic combustion of semi-coke

2021 ◽  
Vol 10 (1) ◽  
pp. 011-020
Author(s):  
Luyao Kou ◽  
Junjing Tang ◽  
Tu Hu ◽  
Baocheng Zhou ◽  
Li Yang
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Combustion Rate ◽  
Activation Energies ◽  
Combustion Reaction ◽  
Tg Analysis ◽  
Conversion Rates ◽  
Apparent Activation Energies ◽  
Ozawa Integral Method ◽  
Addition Amount

Abstract Generally, adding a certain amount of an additive to pulverized coal can promote its combustion performance. In this paper, the effect of CaO on the combustion characteristics and kinetic behavior of semi-coke was studied by thermogravimetric (TG) analysis. The results show that adding proper amount of CaO can reduce the ignition temperature of semi-coke and increase the combustion rate of semi-coke; with the increase in CaO content, the combustion rate of semi-coke increases first and then decreases, and the results of TG analysis showed that optimal addition amount of CaO is 2 wt%. The apparent activation energy of CaO with different addition amounts of CaO was calculated by Coats–Redfern integration method. The apparent activation energy of semi-coke in the combustion reaction increases first and then decreases with the increase in CaO addition. The apparent activation energies of different samples at different conversion rates were calculated by Flynn–Wall–Ozawa integral method. It was found that the apparent activation energies of semi-coke during combustion reaction decreased with the increase in conversion.

scholarly journals Superior Degradation Performance of Nanoporous Copper Catalysts on Methyl Orange

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 913
Author(s):  
Jinyi Wang ◽  
Sen Yang
Keyword(s):  
Activation Energy ◽  
Methyl Orange ◽  
High Efficiency ◽  
Low Cost ◽  
Degradation Process ◽  
Copper Catalysts ◽  
Reaction Rate Constant ◽  
Nanoporous Structure ◽  
Intra Particle Diffusion ◽  
Different Temperatures

The development of low-cost and high-efficiency catalysts for wastewater treatment is of great significance. Herein, nanoporous Cu/Cu2O catalysts were synthesized from MnCu, MnCuNi, and MnCuAl with similar ligament size through one-step dealloying. Meanwhile, the comparisons of three catalysts in performing methyl orange degradation were investigated. One of the catalysts possessed a degradation efficiency as high as 7.67 mg·g−1·min−1. With good linear fitting by the pseudo-first-order model, the reaction rate constant was evaluated. In order to better understand the degradation process, the adsorption behavior was considered, and it was divided into three stages based on the intra-particle diffusion model. Three different temperatures were applied to explore the activation energy of the degradation. As a photocatalytic agent, the nanoporous structure of Cu/Cu2O possessed a large surface area and it also had low activation energy, which were beneficial to the excellent degradation performance.

Effect of orienting coatings on the apparent activation energy of boundary film destruction

2007 ◽  
Vol 28 (1) ◽  
pp. 12-18 ◽  
Author(s):  
I. A. Buyanovskii ◽  
Yu. N. Drozdov ◽  
Z. V. Ignatieva ◽  
T. M. Savinova ◽  
V. A. Levchenko ◽  
...  
Keyword(s):  
Activation Energy ◽  
Apparent Activation Energy ◽  
Boundary Film

Methanation on exfoliated and supported MoS2

1989 ◽  
Vol 67 (5) ◽  
pp. 862-866 ◽  
Author(s):  
Guenter A. Scholz ◽  
S. Roy Morrison
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Transition Metal Catalysts ◽  
Surface Species ◽  
Reaction Products ◽  
Third Order ◽  
Ammonium Heptamolybdate ◽  
First Order ◽  
Methanation Reaction ◽  
Improved Performance

The methanation reaction on MoS2 exfoliated to a thickness of a few layers or less and adsorbed onto alumina is found to be very small. However, by calcining and resulfiding the exfoliated MoS2 catalysts, greatly improved performance is achieved that is at least equal to the commercial catalysts based on ammonium heptamolybdate. The creation of molybdenum oxysulflde surface species therefore appears to be a necessary step toward producing significant methanation rates with exfoliated and supported MoS2. The methanation products are almost exclusively CO2 and CH4, their mole ratios near unity, with otherwise only very much smaller amounts of longer chain hydrocarbons. The activation energy for methanation is generally observed to be near 100 kJ/mol, with the overall reaction being first order in the carbon monoxide concentration and third order in the hydrogen concentration. In contrast to the transition-metal catalysts, no water could be detected in the reaction products of the molybdenum based catalyst. Keywords: methanation reaction on MoS2, exfoliated and supported MoS2 as catalyst.

scholarly journals Influence of dimensionality on phase transition in VO2 nanocrystals

2013 ◽  
Vol 45 (3) ◽  
pp. 305-311 ◽  
Author(s):  
V.A. Blagojevic ◽  
N. Obradovic ◽  
N. Cvjeticanin ◽  
D.M. Minic
Keyword(s):  
Phase Transition ◽  
Activation Energy ◽  
Transition Temperature ◽  
Apparent Activation Energy ◽  
Phase Transition Temperature ◽  
Bulk Material ◽  
Two Dimensional ◽  
Lower Phase ◽  
One Dimensional ◽  
Simultaneous Movement

Hydrothermally synthesized one-dimensional and two-dimensional nanocrystals of VO2 undergo phase transition around 65?C, where temperature and mechanism of phase transition are dependent on dimensionality of nanocrystals. Both nanocrystalline samples exhibit depression of phase transition temperature compared to the bulk material, the magnitude of which depends on the dimensionality of the nanocrystal. One-dimensional nanoribbons exhibit lower phase transition temperature and higher values of apparent activation energy than two-dimensional nanosheets. The phase transition exhibits as a complex process with somewhat lower value of enthalpy than the phase transition in the bulk, probably due to higher proportion of surface atoms in the nanocrystals. High values of apparent activation energy indicate that individual steps of the phase transition involve simultaneous movement of large groups of atoms, as expected for single-domain nanocrystalline materials.

scholarly journals Apparent Activation Energy in Electrochemical Multistep Reactions: A Description via Degrees of Rate Control

2020 ◽  
Author(s):  
Alfredo Calderón-Cárdenas ◽  
Enrique A. Paredes-Salazar ◽  
Hamilton Varela
Keyword(s):  
Activation Energy ◽  
Catalytic Activity ◽  
Apparent Activation Energy ◽  
Chemical Kinetics ◽  
Rate Control ◽  
Rate Coefficients ◽  
Intrinsic Activity ◽  
Empirical Parameter ◽  
Heterogenous Catalysis ◽  
Multistep Reactions

<div> <div> <div> <p>Activation energy is a well-known empirical parameter in chemical kinetics that characterises the dependence of the chemical rate coefficients on the temperature and provides information to compare the intrinsic activity of the catalysts. However, the determination and interpretation of the apparent activation energy in multistep reactions is not an easy task. For this purpose, the concept of degree of rate control is convenient, which comprises a mathematical approach for analyzing reaction mechanisms and chemical kinetics. Although this concept has been used in catalysis, it has not yet been applied in electrocatalytic systems, whose ability to control the potential across the solid/liquid interface is the main difference with heterogenous catalysis, and the electrical current is commonly used as a measure of the reaction rate. Herein we use the definition of ‘degree of rate control for elementary step’ to address some of the drawbacks that frequently arise with interpreting apparent activation energy as a measure of intrinsic electrocatalytic activity of electrode. For this, an electrokinetic model Langmuir-Hinshelwood-like is used for making numerical experiments and verifying the proposed ideas. The results show that to improve the catalytic activity of an electrode material, it must act upon the reaction steps with the highest normalised absolute values of degree of rate control. On the other hand, experiments at different applied voltages showed that if the electroactive surface poisoning process take place, changes in 𝐸𝑎𝑝𝑝 can not be used to compare the catalytic activity of the electrodes. Finally, the importance of making measurements at steady-state to avoid large errors in the calculations of apparent activation energy is also discussed. </p> </div> </div> </div>

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