scholarly journals The Reduction Behavior of Ocean Manganese Nodules by Pyrolysis Technology Using Sawdust as the Reductant

Minerals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 850 ◽  
Author(s):  
Xiang-yi Deng ◽  
Dong-sheng He ◽  
Ru-an Chi ◽  
Chun-qiao Xiao ◽  
Jin-gang Hu
Keyword(s):  
Activation Energy ◽  
High Efficiency ◽  
Acid Leaching ◽  
Reduction Process ◽  
Reduction Reaction ◽  
Pyrolysis Process ◽  
Manganese Nodules ◽  
Valuable Metals ◽  
Shrinking Core ◽  
Isothermal Kinetic

Ocean manganese nodules, which contain abundant Cu, Co, Ni and Mn resources, were reduced using biomass (sawdust) pyrolysis technology. Valuable metals were further extracted by acid leaching after the reduction process with high efficiency. The effects of sawdust dosage, reduction temperature, and time were investigated to obtain optimal operating parameters. The extraction rates of Mn, Cu, Co, and Ni reached as high as 96.1%, 91.7%, 92.5%, and 94.4%, respectively. Results from TGA show that the main pyrolysis process of sawdust occurs at temperature range of 250–375 °C with a mass loss of 59%, releasing a large amount of volatile substances to reduce the ocean manganese nodules. The pyrolysis activation energy of sawdust was calculated to be 52.68 kJ∙mol−1 by the non-isothermal kinetic model. Additionally, the main reduction reaction behind the main sawdust pyrolysis process was identified by the comparison of the assumed and actual TG curve. The thermodynamic analysis showed that the high valence manganese minerals were gradually reduced to Mn2O3, Mn3O4, and MnO by CO generated from sawdust pyrolysis. The shrinking core model showed that the reduction process is controlled by the surface chemical reaction with activation energy of 45.5 kJ∙mol−1. The surface of reduced ore and acid leached residue exhibited a structure composed of relatively finer pores and rougher morphology than the raw ore.

Mechanism and Kinetics of Pyrolysis of Coal With High Ash and Low Fixed Carbon Contents

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Lin Yang ◽  
Jing-yu Ran ◽  
Li Zhang
Keyword(s):  
Activation Energy ◽  
High Efficiency ◽  
Diffusion Mechanism ◽  
Volatile Matter ◽  
Global Symmetry ◽  
Pyrolysis Process ◽  
Heating Rates ◽  
Characteristic Index ◽  
Pyrolysis Reaction ◽  
Second Stage

There are much coal with low content of volatile matter (Vad < 20%), high content of ash (Aad > 50%), low heating caloric (∼10,000 kJ/kg) in China. It is very important to study pyrolysis performance of the coal to ensure high efficiency of utilization and low pollution emissions. In this paper, we study the pyrolysis reaction details of different types of this coal from different regions of China under different pyrolysis pressures, temperatures, particle sizes, and heating rates by thermo-gravimetry (TG) method. The pyrolysis characteristic temperatures and the characteristic index of volatilization matter released of coal gangue (CG) are obtained in this work. In addition, the detailed process of mechanism and kinetic parameters of pyrolysis are presented. The results show that many factors have an obvious influence on the pyrolysis reaction of the coal. The pyrolysis process of the coal is comprised of two stages. At the primary stage(t < 560 °C), the pyrolysis reaction is dominated by the diffusion rate of volatile matter because of the high ash content, which is the global symmetry diffusion mechanism, and the volatile matter of this stage is more difficult to come out and a high pyrolysis activation energy is observed. With increasing pyrolysis temperature, the pyrolysis reaction is moving into diffusion limitation, the volatile matter is released plentifully, and the low activation energy is found. At the second stage (t > 560 °C), the pyrolysis reaction is governed by the tar-released reaction and the pyrolysis reaction order is 1.5. The high activation energy is also observed for the second stage pyrolysis process.

scholarly journals Kinetic Study of the Leaching of Iraqi Akashat Phosphate Ore Using Lactic Acid

2018 ◽  
Vol 14 (1) ◽  
pp. 128-135
Author(s):  
Mohammed Y. Eisa ◽  
Basma A. Abdulmajeed ◽  
C. K. Hawee
Keyword(s):  
Activation Energy ◽  
Lactic Acid ◽  
Kinetic Study ◽  
Weight Ratio ◽  
Acid Leaching ◽  
Reaction Rate Constant ◽  
Selective Leaching ◽  
Reaction Conditions ◽  
Phosphate Ore ◽  
Shrinking Core

     In the present work, a kinetic study was performed to the extraction of phosphate from Iraqi Akashat phosphate ore using organic acid. Leaching was studied using lactic acid for the separation of calcareous materials (mainly calcite). Reaction conditions were 2% by weight acid concentration and 5ml/gm of acid volume to ore weight ratio. Reaction time was taken in the range 2 to 30 minutes (step 2 minutes) to determine the reaction rate constant k based on the change in calcite concentration. To determine value of activation energy when reaction temperature is varied from 25 to 65 , another investigation was accomplished. Through the kinetic data, it was found that selective leaching was controlled by surface chemical reaction. The study showed that the reaction kinetics was specifically described by the shrinking core model (SCM). Regression analyses gave values of activation energy (Ea) and Arrhenius constant (ko) as 40.108 KJ/mole and (2.256 103 sec-1) respectively.

scholarly journals Electrocatalysis for Oxygen Reduction Reaction on EDTAFeNa and Melamine co-Derived Self-Supported Fe-N-C Materials

Catalysts ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 623
Author(s):  
Mengfan Shen ◽  
Ziwei Meng ◽  
Tong Xue ◽  
Hongfang Shen ◽  
Xiang-Hui Yan
Keyword(s):  
Oxygen Reduction Reaction ◽  
Oxygen Reduction ◽  
Large Scale ◽  
Acid Leaching ◽  
Reduction Reaction ◽  
Scale Production ◽  
Final Annealing ◽  
High Performing ◽  
Half Wave ◽  
Mesoscopic Structure

To explore high-performing alternatives to platinum-based catalysts is highly desirable for lowering costs and thus promoting fuel cell commercialization. Herein, self-supported Fe-N-C materials were prepared by the pyrolysis of dual precursors including EDTA ferric sodium (EDTAFeNa) and melamine (MA), followed by acid-leaching and final annealing. Towards an oxygen reduction reaction (ORR) in 0.1 M KOH, the as-prepared MA/EDTAFeNa-HT2 delivered onset (Eonset) and half-wave (E1/2) potentials of 0.97 and 0.84 V vs. RHE, respectively, identical with that of a state-of-the-art Pt/C catalyst, accompanied with predominantly a four-electron pathway. The introduction of MA and extension of acid-leaching promoted a positive shift of 50 mV for E1/2 relative to that of only the EDTAFeNa-derived counterpart. It was revealed that the enhancement of ORR activity is attributed to a decrease in magnetic Fe species and increase in pyridinic/quanternary nitrogen content whilst nearly excluding effects of the graphitization degree, variety of crystalline iron species, and mesoscopic structure. The usage of dual precursors exhibited great potential for the large-scale production of inexpensive and efficient Fe-N-C materials.

scholarly journals Recovery of Zinc and Silver from Zinc Acid-Leaching Residues with Reduction of Their Environmental Impact Using a Novel Water Leaching-Flotation Process

Minerals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 586
Author(s):  
Yunpeng Du ◽  
Xiong Tong ◽  
Xian Xie ◽  
Wenjie Zhang ◽  
Hanxu Yang ◽  
...  
Keyword(s):  
Hazardous Waste ◽  
Acid Leaching ◽  
Copper Recovery ◽  
Water Leaching ◽  
Flotation Process ◽  
Metal Levels ◽  
Valuable Metals ◽  
Leaching Experiments ◽  
Zinc Hydrometallurgy ◽  
Poor Stability

Zinc-leaching residue (ZLR) is a strongly acidic hazardous waste; it has poor stability, high heavy metal levels, and releases toxic elements into the environment. ZLR has potential as a valuable resource, because it contains elevated levels of zinc and silver. In this paper, the recovery of zinc (Zn) and silver (Ag) from ZLR wastes from zinc hydrometallurgy workshops using water leaching followed by flotation was studied. During water leaching experiments, the zinc and copper recovery rates were 38% and 61%, respectively. Thereafter, various flotation testing parameters were optimized and included grinding time, reagent dosages, pulp density, flotation time, and type of adjuster. Experimental results demonstrated this flotation method successfully recycled Ag and Zn. A froth product containing more than 9256.41 g/t Ag and 12.26% Zn was produced from the ZLR with approximately 80.32% Ag and 42.88% Zn recoveries. The toxicity characteristic leaching procedure (TCLP) results indicated the water-leaching flotation process not only recycled valuable metals such as zinc and silver in zinc-containing hazardous wastes but lowered the hazardous waste levels to those of general wastes and recycled wastes in an efficient, economical, and environmentally friendly way.

scholarly journals Quasi-graphitic carbon shell-induced Cu confinement promotes electrocatalytic CO2 reduction toward C2+ products

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ji-Yong Kim ◽  
Deokgi Hong ◽  
Jae-Chan Lee ◽  
Hyoung Gyun Kim ◽  
Sungwoo Lee ◽  
...  
Keyword(s):  
High Efficiency ◽  
Co2 Reduction ◽  
Value Added ◽  
Material Design ◽  
Catalyst System ◽  
Critical Issue ◽  
Reduction Reaction ◽  
Catalyst Design ◽  
Design Strategies ◽  
Faradaic Efficiency

AbstractFor steady electroconversion to value-added chemical products with high efficiency, electrocatalyst reconstruction during electrochemical reactions is a critical issue in catalyst design strategies. Here, we report a reconstruction-immunized catalyst system in which Cu nanoparticles are protected by a quasi-graphitic C shell. This C shell epitaxially grew on Cu with quasi-graphitic bonding via a gas–solid reaction governed by the CO (g) - CO2 (g) - C (s) equilibrium. The quasi-graphitic C shell-coated Cu was stable during the CO2 reduction reaction and provided a platform for rational material design. C2+ product selectivity could be additionally improved by doping p-block elements. These elements modulated the electronic structure of the Cu surface and its binding properties, which can affect the intermediate binding and CO dimerization barrier. B-modified Cu attained a 68.1% Faradaic efficiency for C2H4 at −0.55 V (vs RHE) and a C2H4 cathodic power conversion efficiency of 44.0%. In the case of N-modified Cu, an improved C2+ selectivity of 82.3% at a partial current density of 329.2 mA/cm2 was acquired. Quasi-graphitic C shells, which enable surface stabilization and inner element doping, can realize stable CO2-to-C2H4 conversion over 180 h and allow practical application of electrocatalysts for renewable energy 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.

Reduction Kinetics of Mill Scale Briquettes by Using A3 Fine Coal as a Reductant

2021 ◽  
Vol 21 (4) ◽  
pp. 2563-2567
Author(s):  
Nguyen Hoang Viet ◽  
Pham Ngoc Dieu Quynh ◽  
Nguyen Thi Hoang Oanh
Keyword(s):  
Reaction Rate ◽  
Reduction Process ◽  
Reduction Reaction ◽  
Reaction Rate Constant ◽  
Reduction Degree ◽  
Furnace Temperature ◽  
Time Duration ◽  
Mill Scale ◽  
Fine Coal ◽  
Kinetics Of

In this work, a mixture of mill scale with 5 wt% molasses as binder was pressed under pressure of 200 MPa to prepare briquettes. The reduction process was performed at the temperature of 1000, 1050, 1100, 1150 and 1200 °C in the bed of A3 fine coal as the reductant. The degree of reduction was evaluated at time duration of 15, 30, 45, 60, 90 and 150 minutes, after the furnace temperature reached the predetermined reduction temperature. The highest reduction degree is 94.7% at the reduction process temperature of 1200 °C. Reaction rate constant (k) increased from 4.63×10-4 to 5.03×10-3 min-1 when the temperature increased from 1000 to 1200 °C. The apparent activation energy of the reduction reaction (Ea) is about 95.6 kJ/mole.

Leaching Behavior Analysis of Valuable Metals from Lithium-Ion Batteries Cathode Material

2018 ◽  
Vol 775 ◽  
pp. 419-426 ◽  
Author(s):  
Wei Sheng Chen ◽  
Hsing Jung Ho
Keyword(s):  
Cathode Material ◽  
Lithium Ion Batteries ◽  
Acid Leaching ◽  
Lithium Ion ◽  
Activation Energies ◽  
Mass Ratio ◽  
Solid Mass ◽  
Environmental Technology ◽  
Valuable Metal ◽  
Valuable Metals

The paper concerns an approach about using environmental technology and hydrometallurgical process to the recovery of valuable metal from waste cathode material produced during the manufacture of lithium-ion batteries. It is noteworthy that the content of nickel, manganese and cobalt from cathode material are in the extraordinary large proportion. In the acid leaching step, the essential effects of H2SO4 concentration, H2O2 concentration, leaching time, liquid-solid mass ratio and reaction temperature with the leaching percentage were investigated. The cathode material was leached with 2M H2SO4 and 10 vol.% H2O2 at 70 °C and 300 rpm using a liquid-solid mass ratio of 30 ml/g and the leaching efficiency of cobalt was 98.5%, lithium was 99.8%, nickel was 98.6% and manganese was 98.6% under optimum conditions. Kinetic study demonstrates the activation energies for those analyzed metals with Arrhenius equation and manifests the data with hybrid reaction control mechanism. The process was proved from activation energies ranged from 27.79 to 47.25 kJ/mol. Finally, the valuable metals will be leached in sulfuric acid effectively.

scholarly journals Influence of sodium carbonate addition on weight loss of bagasse alkaline black liquor during pyrolysis

BioResources ◽  
2020 ◽  
Vol 15 (2) ◽  
pp. 2428-2441
Author(s):  
Xusheng Li ◽  
Jinlong Wang ◽  
Derong Yan ◽  
Yongjun Yin ◽  
Shuangfei Wang
Keyword(s):  
Activation Energy ◽  
Weight Loss ◽  
Sodium Carbonate ◽  
Black Liquor ◽  
Reduction Reaction ◽  
Loss Ratio ◽  
N2 Atmosphere ◽  
Microscopic Morphology ◽  
Weight Loss Ratio

To understand the effects and the mechanism of sodium carbonate (Na2CO3) addition on the bagasse alkaline black liquor (BABL) pyrolysis, the reaction variables such as temperature, heating rate, and amount of Na2CO3 addition into BABL-solids were investigated under N2 atmosphere from 50 °C to 1000 °C by thermogravimetic analysis (TGA). Scanning electron microscopy (SEM) and the Coats–Redfern method (CRM) were employed for surface microscopic morphology observations and kinetic analysis, respectively. The results showed that Na2CO3 plays an inhibiting and promoting role during devolatilization (200 °C to 650 °C) and the reduction stages (650 °C to 1000 °C), respectively. Adding Na2CO3 into BABL-solids tends to increase the thickness of the salt layer covering the BABL-solids surface, which increases the activation energy and reduces the weight loss ratio of BABL-solids pyrolysis within 200 °C to 650 °C. Adding Na2CO3 into the BABL-solids tends to increase the number of alkaline compounds or the active site of the reduction reaction, which reduces the activation energy and increases the weight loss ratio of BABL-solids pyrolysis within 650 °C to 1000 °C. The role of Na2CO3 as an additive could be well understood by studying the influence mechanism of Na2CO3 on BABL-solids pyrolysis.

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