scholarly journals Effect of redox potential on chalcopyrite dissolution imposed by addition of ferrous ions

2017 ◽  
Vol 42 (1) ◽  
pp. 40 ◽  
Author(s):  
Ana Laura Araújo Santos ◽  
Fabiana Antonia Arena ◽  
Assis Vicente Benedetti ◽  
Denise Bevilaqua
Keyword(s):  
Redox Potential ◽  
Acid Leaching ◽  
Dissolution Kinetics ◽  
Sem Analysis ◽  
Conclusive Evidence ◽  
Copper Recovery ◽  
Potential Range ◽  
Ferrous Ions ◽  
Copper Dissolution

Copper is a metal with a great economic interest and about 70% is found in nature in chalcopyrite form (CuFeS2). However the chalcopyrite dissolution is a challenge for industries as well as researchers because of its slow dissolution kinetics. The control of redox potential is one factor that can help in this drawback. This study was undertaken to evaluate the role of redox potential on chalcopyrite bioleaching by addition of ferrous ions. Acid leaching with addition of ferrous ions promoted high dissolution of chalcopyrite by the maintenance of low redox potential (420 mV/Ag/AgCl). On the other hand, the copper dissolution in bacterial systems showed low copper recovery (610 mV/Ag/AgCl). XRD of solid residues showed in abiotic conditions the formation of elemental sulfur, jarosites and a significant decrease on chalcopyrite’s peaks. In bacterial conditions, only jarosites was detected as new crystalline phase. SEM analysis confirmed the results obtained by XRD. In general, the results showed conclusive evidence that the maintenance of low redox potential and the addition of ferrous ions have positively influenced the copper recovery and confirmed the literature data, which indicate a critical potential range where chalcopyrite leaching is more favorable.

Role of pyrite in sulfuric acid leaching of chalcopyrite: An elimination of polysulfide by controlling redox potential

2016 ◽  
Vol 164 ◽  
pp. 159-165 ◽  
Author(s):  
Hongbo Zhao ◽  
Jun Wang ◽  
Xiaowen Gan ◽  
Minghao Hu ◽  
Lang Tao ◽  
...  
Keyword(s):  
Sulfuric Acid ◽  
Redox Potential ◽  
Acid Leaching ◽  
Sulfuric Acid Leaching

scholarly journals Copper Dissolution from Black Copper Ore under Oxidizing and Reducing Conditions

Metals ◽  
2019 ◽  
Vol 9 (7) ◽  
pp. 799 ◽  
Author(s):  
Oscar Benavente ◽  
María Cecilia Hernández ◽  
Evelyn Melo ◽  
Damián Núñez ◽  
Víctor Quezada ◽  
...  
Keyword(s):  
Redox Potential ◽  
Dissolution Rate ◽  
Inductively Coupled Plasma ◽  
Amorphous Materials ◽  
Acid Leaching ◽  
Copper Sample ◽  
Iron Sulfate ◽  
Copper Extraction ◽  
Copper Dissolution ◽  
Reducing Conditions

Black copper oxides are amorphous materials of copper-bearing phases of manganese. They are complex mineral compounds with difficult to recognize mineralogy and have slow dissolution kinetics in conventional hydrometallurgical processes. This study evaluates the effects of various leaching media on copper dissolution from black copper minerals. Leach of a pure black copper sample from Lomas Bayas Mine and another from a regional mine were characterized by inductively coupled plasma atomic emission spectroscopy (ICP-AES), X-ray diffraction (XRD), scanning electron microscopy (SEM), Qemscan and mechanically prepared for acid leaching under standard, oxidizing and reducing conditions through the addition of oxygen, iron sulfate or sulfur dioxide, respectively. Standard and high potential leaching (770 mV (SHE)) results in a copper dissolution rate of 70% and manganese dissolution rate of 2%. The addition of potential reducing agents (FeSO4 or SO2) decreases the redox potential to 696 and 431 mV, respectively, and favors the dissolution of manganese, thus increasing the overall copper extraction rate. The addition of SO2 results in the lowest redox potential and the highest copper extraction rates of 86.2% and 75.5% for the Lomas Bayas and regional samples, respectively, which represent an increase of 15% over the copper extract rates under standard and oxidizing conditions.

Leaching of Zinc Sulfide by Thiobacillus ferrooxidans: Experiments with a Controlled Redox Potential Indicate No Direct Bacterial Mechanism

1998 ◽  
Vol 64 (10) ◽  
pp. 3570-3575 ◽  
Author(s):  
T. A. Fowler ◽  
F. K. Crundwell
Keyword(s):  
Redox Potential ◽  
Zinc Sulfide ◽  
Thiobacillus Ferrooxidans ◽  
Experimental Period ◽  
Electrolytic Cell ◽  
Ferric Ions ◽  
Ferrous Ions ◽  
Bacterial Leaching ◽  
Dissolved Iron

ABSTRACT The role of Thiobacillus ferrooxidans in bacterial leaching of mineral sulfides is controversial. Much of the controversy is due to the fact that the solution conditions, especially the concentrations of ferric and ferrous ions, change during experiments. The role of the bacteria would be more easily discernible if the concentrations of ferric and ferrous ions were maintained at set values throughout the experimental period. In this paper we report results obtained by using the constant redox potential apparatus described previously (P. I. Harvey and F. K. Crundwell, Appl. Environ. Microbiol. 63:2586–2592, 1997). This apparatus is designed to control the redox potential in the leaching compartment of an electrolytic cell by reduction or oxidation of dissolved iron. By controlling the redox potential the apparatus maintains the concentrations of ferrous and ferric ions at their initial values. Experiments were conducted in the presence of T. ferrooxidans and under sterile conditions. Analysis of the conversion of zinc sulfide in the absence of the bacteria and analysis of the conversion of zinc sulfate in the presence of the bacteria produced the same results. This indicates that the only role of the bacteria under the conditions used is regeneration of ferric ions in solution. In this work we found no evidence that there is a direct mechanism for bacterial leaching.

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 On the Use of Iron in Organic Chemistry

Molecules ◽  
2020 ◽  
Vol 25 (6) ◽  
pp. 1349 ◽  
Author(s):  
Arnar Guðmundsson ◽  
Jan-E. Bäckvall
Keyword(s):  
Organic Chemistry ◽  
Redox Potential ◽  
Potential Range ◽  
Coupling Reactions ◽  
Base Metals ◽  
Metal Catalysis ◽  
Iron Catalysis ◽  
Cross Coupling Reactions ◽  
Life On Earth ◽  
Palladium Platinum

Transition metal catalysis in modern organic synthesis has largely focused on noble transition metals like palladium, platinum and ruthenium. The toxicity and low abundance of these metals, however, has led to a rising focus on the development of the more sustainable base metals like iron, copper and nickel for use in catalysis. Iron is a particularly good candidate for this purpose due to its abundance, wide redox potential range, and the ease with which its properties can be tuned through the exploitation of its multiple oxidation states, electron spin states and redox potential. This is a fact made clear by all life on Earth, where iron is used as a cornerstone in the chemistry of living processes. In this mini review, we report on the general advancements in the field of iron catalysis in organic chemistry covering addition reactions, C-H activation, cross-coupling reactions, cycloadditions, isomerization and redox reactions.

scholarly journals Role of redox-inactive metals in controlling the redox potential of heterometallic manganese–oxido clusters

2021 ◽  
Author(s):  
Keisuke Saito ◽  
Minesato Nakagawa ◽  
Manoj Mandal ◽  
Hiroshi Ishikita
Keyword(s):  
Photosystem Ii ◽  
Redox Potential ◽  
Quantum Chemical Calculations ◽  
Catalytic Reaction ◽  
Quantum Chemical ◽  
Ionic Radius ◽  
Redox Potentials ◽  
Oxygen Evolving ◽  
Highest Occupied Molecular Orbitals

AbstractPhotosystem II (PSII) contains Ca2+, which is essential to the oxygen-evolving activity of the catalytic Mn4CaO5 complex. Replacement of Ca2+ with other redox-inactive metals results in a loss/decrease of oxygen-evolving activity. To investigate the role of Ca2+ in this catalytic reaction, we investigate artificial Mn3[M]O2 clusters redox-inactive metals  [M] ([M]  = Mg2+, Ca2+, Zn2+, Sr2+, and Y3+), which were synthesized by Tsui et al. (Nat Chem 5:293, 2013). The experimentally measured redox potentials (Em) of these clusters are best described by the energy of their highest occupied molecular orbitals. Quantum chemical calculations showed that the valence of metals predominantly affects Em(MnIII/IV), whereas the ionic radius of metals affects Em(MnIII/IV) only slightly.

scholarly journals CHEK2∗1100delC Mutation and Risk of Prostate Cancer

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Victoria Hale ◽  
Maren Weischer ◽  
Jong Y. Park
Keyword(s):  
Prostate Cancer ◽  
Current Knowledge ◽  
Prostate Cancer Screening ◽  
Critical Role ◽  
Prostate Cancer Risk ◽  
Conclusive Evidence ◽  
Increased Risk ◽  
History Of ◽  
Cancer Studies

Although the causes of prostate cancer are largely unknown, previous studies support the role of genetic factors in the development of prostate cancer.CHEK2plays a critical role in DNA replication by responding to double-stranded breaks. In this review, we provide an overview of the current knowledge of the role of a genetic variant, 1100delC, ofCHEK2on prostate cancer risk and discuss the implication for potential translation of this knowledge into clinical practice. Currently, twelve articles that discussedCHEK2∗1100delC and its association with prostate cancer were identified. Of the twelve prostate cancer studies, five studies had independent data to draw conclusive evidence from. The pooled results of OR and 95% CI were 1.98 (1.23–3.18) for unselected cases and 3.39 (1.78–6.47) for familial cases, indicating thatCHEK2∗1100delC mutation is associated with increased risk of prostate cancer. Screening for CHEK2∗1100delC should be considered in men with a familial history of prostate cancer.

The influence of thickness of CrN coating on the durability of hot forging dies

2011 ◽  
Vol 1 (2) ◽  
Author(s):  
Jerzy Smolik
Keyword(s):  
Coating Thickness ◽  
Nitrided Layer ◽  
Hot Forging ◽  
Sem Analysis ◽  
Internal Stresses ◽  
Main Role ◽  
Hybrid Layer ◽  
Crn Coating ◽  
Forging Process

AbstractThis article presents results which enabled the determination of the role of CrN coating and the influence of its thickness on the effectiveness of hybrid layer “nitrided layer / CrN coating” in the process of increasing the durability of forging dies. Dies coated with hybrid layers “nitrided layer / CrN coating” with various CrN coating thickness were — after different maintenance periods — subjected to metallographic testing, 3D shape testing and SEM analysis. Hardness distribution was also determined. The obtained results revealed that for all tested dies, independently from CrN coating thickness, the main mechanisms of their destruction was mechanical and thermal fatigue, and plastic deformation. It has been shown that the main role of CrN coating in the hybrid layer ”nitrided layer / PVD coating” is to counteract a high temperature influence the source of which is forging on die material. In order to do so the CrN coating should be characterized by a considerably lower thermal conductivity coefficient to steel and low hardness so that it can efficiently resist fatigue processes in the forging process. Based on testing conducted by means of the sin 2 φ method, it was revealed that internal stresses are vitally important for CrN coating for fatigue resistance of hybrid layer ”nitrided layer / CrN coating” during the forging process.

Synthesis of Magnesia Powder from East Java Dolomite through Leaching, Precipitation and Calcination

2015 ◽  
Vol 1112 ◽  
pp. 550-554
Author(s):  
M. Zaki Mubarok ◽  
Christian Adi Kurniawan
Keyword(s):  
Particle Diameter ◽  
Acid Leaching ◽  
Xrd Analysis ◽  
Sem Analysis ◽  
Leach Solution ◽  
Water Removal ◽  
Solution Ph ◽  
Crystal Water ◽  
Lower Temperature ◽  
Co Precipitation

At the present paper, a process of magnesia (MgO) synthesis from East Java dolomite through hydrochloride acid leaching, precipitation and calcination as well as characteristic of the product is discussed. Results of the experimental works show that the dissolution rate of magnesium and calcium from dolomite in hydrochloride acid solution was very rapid. Complete magnesium extraction was obtained by the leaching test with acid concentration of 1.5 molar, particle size distribution of -325#, solid-liquid ratio 1:20 (g/mL), stirring speed 200 rpm at room temperature after only 10 seconds. Precipitation of Mg(OH)2 by the addition of 20% (v/v) CaO slurry into pregnant leach solution resulted in 97.5% Mg precipitation after 1 minute. Solution pH must be maintained at a level of 10-10.5 by adjusting CaO addition in order to minimize calcium co-precipitation and to obtain high purity of Mg(OH)2 precipitate. Calcinations of Mg(OH)2 were performed at temperature range of 550-800°C in which 99% of crystal water removal took place after 5 minute at temperature of 800°C. Lower temperature requires longer time of crystalline water removal from Mg(OH)2. XRF analysis showed MgO purity of 88% with the main impurities of calcium and chloride. XRD analysis detected the presences of calcium as calcite (CaCO3) and portlandite (Ca(OH)2) as impurities in the MgO product. SEM analysis of the MgO powder revealed a nano size of MgO with particle diameter of about 50 nm.

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