scholarly journals Leach-SX-EW copper revalorization from overburden of abandoned copper mine Cerovo, Eastern Serbia

2009 ◽  
Vol 45 (1) ◽  
pp. 45-57 ◽  
Author(s):  
Z. Stevanovic ◽  
M. Antonijevic ◽  
R. Jonovic ◽  
Lj. Avramovic ◽  
R. Markovic ◽  
...  
Keyword(s):  
Ph Value ◽  
Cathode Current Density ◽  
Copper Recovery ◽  
Open Pit ◽  
Copper Extraction ◽  
Leaching Tests ◽  
Solution Ph ◽  
Mine Waters ◽  
Leaching Solution ◽  
Cathode Current

Hydrometallurgical processes for copper revalorization from overburden of abandoned mine Cerovo in Eastern Serbia were studied. Paper contain results of percolation leaching tests, performed with acidic mine waters accumulated in the bottom of the former open pit, followed by solvent extraction (SX) and electrowinning (EW) processes on achieved copper pregnant leach solutions. Usage of accumulated waste waters was objected to minimizing the environmental hazard due to uncontrolled leaking of these waters in nearby creeks and rivers. Chemical composition of acidic mine waters used for leaching tests was: (g/dm3): Cu - 0.201; Fe - 0.095; Mn - 0.041; Zn - 0.026; Ni - 0.0004; pH value - 3.3. Copper content in overburden sample used for leaching tests was 0.21% from which 64% were oxide copper minerals. In scope of leaching tests were examined influence of leaching solution pH values and iron (III) concentration on copper recovery. It was established that for 120 hours of leaching on pH=1.5 without oxidant agents, copper concentration in pregnant leach solutions enriched up to 1.08g/dm3 which was enough for copper extraction from solution with SX-EW treatment. As extraction reagent in SX circuit was used LIX-984N in a kerosene diluent. Cathode current density in electrowinning cell was 220Am-2 while electrolyte temperature was kept on 50?2oC. Produced cathode copper at the end of SX-EW process has purity of 99.95% Cu.

scholarly journals Ammoniacal System Mechanisms for Leaching Copper from Converter Slag

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 712
Author(s):  
Alvaro Aracena ◽  
Andrés Valencia ◽  
Oscar Jerez
Keyword(s):  
Particle Size ◽  
Converter Slag ◽  
Research Work ◽  
Ammonium Hydroxide ◽  
Copper Extraction ◽  
Solution Ph ◽  
Intraparticle Diffusion Model ◽  
Electron Microscopy Analysis ◽  
Leaching Solution ◽  
Conversion Stage

In pyrometallurgical processes refining copper, the main source of loss in the conversion stage is from slag. This paper reports on research work treating converter slag containing high percentages of copper (36 wt%) using ammonium hydroxide at room temperature. Variables analyzed are solution pH, agitation, temperature, NH4OH concentration and particle size. Results showed that the hydronium ion resulting from ammonium hydroxide dissociation was the main oxidant of copper compounds in slag, such as CuO, Cu2O and Cu, with the exception of CuFeO2. The particles contain a large amount of microcracks (porosity) in their refractory structure (analyzed by compositional image capture (BSE)). Thus, the diffusion of the leaching solution through the microcracks making contact with the copper oxides would be allowed. Leaching mechanisms were corroborated by X-ray diffraction and scanning electron microscopy analysis. Increasing temperature and NH4OH concentration while decreasing particle size obtained higher copper recoveries, reaching values of 84.8%. Under the same conditions, the main impurity (iron) was minimal (<2%). Solution pH also affected slag leaching. Agitation of the solution positively affected the rate of copper extraction. Leaching kinetics of the leaching solution through the porosity formed in the slag was analyzed under the intraparticle diffusion model. The reaction order was 1.2 with respect to the concentration of ammonium hydroxide and the model was inversely proportional to the square of the particle radius. The activation energy obtained was 42.3 kJ/mol for temperature range 283 to 333 K.

Bituminous Insulations Durability of Underground Metallic Pipelines I Field investigations

2017 ◽  
Vol 68 (3) ◽  
pp. 581-585 ◽  
Author(s):  
Gabriela Oprina ◽  
Ladislau Radermacher ◽  
Daniel Lingvay ◽  
Dorian Marin ◽  
Andreea Voina ◽  
...  
Keyword(s):  
Cathode Current Density ◽  
Induced Voltage ◽  
Cathodic Current ◽  
Field Investigations ◽  
Operation Period ◽  
Cathode Current ◽  
Protection Potential ◽  
Cathodic Protection System ◽  
Corrosion State ◽  
Good Agreement

The corrosion state of an underground metallic pipeline of �161 mm and 565 m length was assessed by specific electrical and electrochemical measurements. The investigated pipe, buried in 1997, was protected against corrosion by successive layers of bituminous material with a total thickness of 1 to 1.2 mm. The pipeline crosses three electrified railway lines (50 Hz - 28 kV), and then its route is approximately parallel to these lines; thus, the induced AC voltages between line and ground were calculated obtaining values between 4.05 and 7.1 Vrms, in good agreement with the values measured in the accessible points. The measurements regarding the insulation capacity against corrosion of the bituminous insulation, performed at one month and after 19 years of burial, showed an increase of the average cathode current density needed for obtaining the protection potential in the range �1.00 � �1.28 VCu/CuSO4 of approx. three times (from 6.65 up to 19.96 mA/m2), in good agreement with the evolution of the insulation resistance measured between the steel pipe (having a contact area with the ground of 270.5 m2) and a ground socket of 4 W, which decreased from 995 to 315 kW. Following the analysis and processing of the field collected data, it is considered that, by implementing a cheap cathodic protection system (without cathodic current power supply), based on the rectification of the AC induced voltage, the safe operation period of the investigated pipeline may be extended by at least 50 years.

RESTORATION OF MACHINE PARTS WITH GALVANIZED ZINC COATINGS

2020 ◽  
Vol 4 (141) ◽  
pp. 140-147
Author(s):  
MIKHAIL VIKHAREV ◽  
◽  
VLADIMIR YUDIN ◽  
VESELOVSKIY NIKOLAY ◽  
◽  
...  
Keyword(s):  
Current Density ◽  
Cathode Surface ◽  
Zinc Coating ◽  
Cathode Current Density ◽  
Research Purpose ◽  
Cathode Layer ◽  
Properties Of Coatings ◽  
Chemical Polarization ◽  
Cathode Current ◽  
Zinc Coatings

The article shows the role of electroplating in the restoration of parts, indicates the advantages of restoring parts with electroplating over other methods, and gives the characteristics and properties of coatings obtained by electroplating. (Research purpose) The research purpose is in increasing the speed of application of zinc electroplating when restoring parts. (Materials and methods) The cathode current density has a decisive influence on the coating speed. The main reason for limiting the cathode current density during galvanizing from sulfuric acid electrolytes is the chemical polarization of the cathode. The article presents a study on the designed installation for the application of galvanic coatings. When applying coatings to the internal surfaces of parts, there was used a device with activating elements having an electromechanical rotation drive. This device prevents depletion of the near-cathode layer of the electrolyte and reduces the chemical polarization of the cathode. Elements made of moisture-resistant skin were used as activators. (Results and discussion) The article presents the results of experiments as a dependence of the coating speed on the speed of the activator relative to the restoring surface. It also presents the relationship between the size of the abrasive grains of the activating elements, the force of their pressing against the cathode surface, the speed of movement of the activator and the speed of applying the zinc coating, as well as its quality. By activating the cathode surface, it was possible to raise the operating current density to 100-150 amperes per square decimeter. The speed of application of zinc coatings is 16-25 micrometers per minute. (Conclusions) In the course of research, authors determined the conditions of electrolysis during galvanizing, which provide a significant increase in the cathode current density and the rate of application of these coatings during the restoration of parts.

scholarly journals Separation of Radionuclides from a Rare Earth-Containing Solution by Zeolite Adsorption

Minerals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 20
Author(s):  
Deniz Talan ◽  
Qingqing Huang
Keyword(s):  
Rare Earth ◽  
Rare Earths ◽  
Contact Time ◽  
Separation Efficiency ◽  
Ph Value ◽  
Solid Phase ◽  
Separation Performance ◽  
Solution Ph ◽  
Zeolite Sample ◽  
Alternative Sources

The increasing industrial demand for rare earths requires new or alternative sources to be found. Within this context, there have been studies validating the technical feasibility of coal and coal byproducts as alternative sources for rare earth elements. Nonetheless, radioactive materials, such as thorium and uranium, are frequently seen in the rare earths’ mineralization, and causes environmental and health concerns. Consequently, there exists an urgent need to remove these radionuclides in order to produce high purity rare earths to diversify the supply chain, as well as maintain an environmentally-favorable extraction process for the surroundings. In this study, an experimental design was generated to examine the effect of zeolite particle size, feed solution pH, zeolite amount, and contact time of solid and aqueous phases on the removal of thorium and uranium from the solution. The best separation performance was achieved using 2.50 g of 12-µm zeolite sample at a pH value of 3 with a contact time of 2 h. Under these conditions, the adsorption recovery of rare earths, thorium, and uranium into the solid phase was found to be 20.43 wt%, 99.20 wt%, and 89.60 wt%, respectively. The Freundlich adsorption isotherm was determined to be the best-fit model, and the adsorption mechanism of rare earths and thorium was identified as multilayer physisorption. Further, the separation efficiency was assessed using the response surface methodology based on the development of a statistically significant model.

scholarly journals Cathodic protection of structures in seawater using solar panels

2019 ◽  
Vol 121 ◽  
pp. 02004
Author(s):  
Boris Borisovich Chernov ◽  
Van Mung Vu ◽  
Anac Maskharovich Nugmanov ◽  
Lyudmila Yuryevna Firsova
Keyword(s):  
Cathodic Protection ◽  
Sea Water ◽  
Cathode Current Density ◽  
Complete Agreement ◽  
Low Alloy Steels ◽  
Solar Panels ◽  
Protective Properties ◽  
Theoretical Concepts ◽  
Alloy Steels ◽  
Cathode Current

It is well known that the cathodic protection of structures in seawater is accompanied by the formation of calcareous deposits on them. In current study, we consider the physicochemical modelling of the formation of the deposit composition against cathode current density in seawater. The reliability of the model representations is confirmed by direct experiments. The work also studied the protective properties of the deposits with a different composition for low-alloy steels in natural sea water. It has been shown that the deposits of pure Mg(OH)2 and the deposits of CaCO3 + Mg(OH)2 had better protective ability against corrosion than the deposits of pure CaCO3. However, the deposits of Mg(OH)2 dissolved faster than the deposits of CaCO3 and CaCO3 + Mg(OH)2. Theoretical concepts and experiments on the laws governing the formation of the deposits and their protective properties are in complete agreement with each other. This allows to use the obtained patterns in the cathodic protection of structures in sea water using solar panels, forming standard deviations with predetermined protective properties in the daytime.

Selective Leaching Nickel from the Pre-Reduced Limonitic Laterite Ore at Atmospheric Pressure

2012 ◽  
Vol 560-561 ◽  
pp. 494-498
Author(s):  
Yong Feng Chang ◽  
Chuan Lin Fan ◽  
Bin Chuan Li ◽  
Xiu Jing Zhai ◽  
Ting An Zhang
Keyword(s):  
Atmospheric Pressure ◽  
Ph Value ◽  
Test Results ◽  
Selective Leaching ◽  
Nickel Extraction ◽  
Extraction Degree ◽  
Leaching Solution ◽  
Novel Method ◽  
Leaching Condition ◽  
Laterite Ore

In this paper a novel method for selective leaching nickel from pre-reduced laterite ore at atmospheric pressure was reported. The reduced calcine was leached in thin acid liquor to liberate the nickel and iron together firstly. By properly controlling the leaching condition, the leached iron ion could hydrolyze as goethite precipitate and regenerate the acid consumed in the leaching procedure. Finally, the nickel is selectively extracted into the leaching solution. The main factors in the leaching process, such as reduction degree of the laterite ore, acidity of the leaching solution were investigated as influence on the nickel extraction. The test results showed that selectively leaching of nickel could be achieved with an extraction degree up to 90% by reducing most of the iron in the lateritic ore to wuestite and controlling the pH value of the leaching solution below 2.5.

Synthesis and Application of Itaconic Acid Water-Coke Slurry Dispersant

2017 ◽  
Vol 896 ◽  
pp. 167-174 ◽  
Author(s):  
Zhi Yuan Yang ◽  
Zhuo Yue Meng ◽  
Zhi Hua Li ◽  
Si Tong Wang
Keyword(s):  
Surface Tension ◽  
Polyethylene Glycol ◽  
Itaconic Acid ◽  
High Performance ◽  
Ph Value ◽  
Raw Materials ◽  
Esterification Reaction ◽  
Solution Ph ◽  
Powder Surface ◽  
Coke Powder

Polyethylene glycol (PEG-200) and itaconic acid (IA) were used as raw materials to compound macromer through esterification reaction. A new type of specialized water-coke slurry dispersant was synthesized by copolymerization of microware, sodium methallyl sulfonate (SMAS) and maleic anhydride (MA). The experiment showed that the concentration of slurry could be reached to 63% with the dosage of 0.2%, and the apparent viscosity was 1140.3 mPa∙s. Through the analysis of the infrared, the dispersant was confirmed to have polyethylene glycol branched chain and hydrophilic functional groups such as carboxyl or sulfonic group. When the concentration of dispersant was 30 g/L, the surface tension of water could be decreased from 72.70 mN/m to 45.50 mN/m. Furthermore, when the solution pH value was 9, the Zeta potential of semi-coke powder surface could also be decreased from-13.38 mV to-25 mV with the addition of dispersant. Thus, this dispersant could increase electronegativity of semi-coke powder surface, enhance steric-hindrance effect and prevent the phenomenon of powder flocculation and gather. Meantime, it also could reinforce the semi-coke hydrophilic by reducing the surface tension of water effectively. And then, the high performance water-coke slurry could be obtained.

scholarly journals CO2 mineralization by olivine at hydrothermal conditions

2014 ◽  
Vol 78 (6) ◽  
pp. 1473-1477
Author(s):  
Jan Přikryl ◽  
Andri Stefánsson
Keyword(s):  
Ph Value ◽  
Hydrothermal Conditions ◽  
Solution Ph ◽  
Rock Interaction ◽  
Carbonate Formation ◽  
Effects Of Temperature ◽  
Co2 Mineralization ◽  
Geochemical Reaction ◽  
Insight Into ◽  
Water Rock Interaction

The interaction of CO2-rich water with olivine was studied using geochemical reaction modelling in order to gain insight into the effects of temperature, acid supply (CO2) and extent of reaction on the secondary mineralogy, water chemistry and mass transfer. Olivine (Fo93) was dissolved at 150 and 250ºC and pCO2 of 2 and 20 bar in a closed system and an open system with secondary minerals allowed to precipitate. The progressive water–rock interaction resulted in increased solution pH, with gradual carbonate formation starting at pH 5 and various Mg-OH and Mg-Si minerals becoming dominant at pH>8. The major factor determining olivine alteration is the pH of the water. In turn, the pH value is determined by acid supply, reaction progress and temperature.

The Study about Environmentally-Friendly Passivation Technology Process and Performance on Brass Surface

2011 ◽  
Vol 399-401 ◽  
pp. 1967-1971
Author(s):  
Hong Yin Xu ◽  
Li Li
Keyword(s):  
Corrosion Resistance ◽  
Phytic Acid ◽  
Passive Film ◽  
Ph Value ◽  
Sodium Molybdate ◽  
Solution Ph ◽  
Sulfosalicylic Acid ◽  
Passivation Film ◽  
Brass Surface ◽  
And Performance

The paper through the synergy before mixed Phytic acid and Sodium molybdate, Sulfosalicylic acid, Organic silane, and add the active substances PEG, Optimize the Passivation liquid formula of Brass surface, Phytic acid is the main ingredient, study the affection of Phytic acid Passive film Corrosion resistance on the three main Passivation conditions: Passivation temperature, time and Passivation solution PH value. The results show that，Phytic acid passivation film process recipes as follows：Phytic acid (quality score 50%) 2~5ml/L, sodium molybdate 4~8g/L, organic material 10~30ml/L, sulfosalicylic acid 3~7g/L, polyethylene glycol 2~6g/L, deactivated temperature 30~35°C, pH value 5, deactivated time 60s. The test showed that，the phytic acid passive film can obviously enhance the anti-corrosive performance on the brass surface, its corrosion resistance proportion chromates passive film is fairly good.

scholarly journals Effects of Fe+2 and Fe+3 in Pretreatment and Leaching on a Mixed Copper Ore in Chloride Media

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 866
Author(s):  
María E. Taboada ◽  
Pía C. Hernández ◽  
Aldo P. Padilla ◽  
Nathalie E. Jamett ◽  
Teófilo A. Graber
Keyword(s):  
Chloride Concentration ◽  
Solution Concentration ◽  
Copper Extraction ◽  
Curing Time ◽  
Ferrous Ions ◽  
Copper Ore ◽  
Second Stage ◽  
Acid Consumption ◽  
Nacl Concentration ◽  
Leaching Solution

A study of the pretreatment stage and subsequent leaching of a mixed copper ore with different chloride solutions containing iron was carried out. The first stage considered pretreatment tests to decide the best conditions. Two levels of each factor were analyzed, 20 and 50 kg/t of NaCl, 17 and 25 kg/t of H2SO4, 0 and 25 kg/t of Fe2(SO4)3·9.2H2O, 0 and 25 kg/t of Fe2SO4·7H2O, and a curing time of 15 and 30 days. The results showed a significant effect of NaCl and curing time on the extraction, and less effect was found with the variation of acid and iron salts. The second stage included column leaching using a solution with 0.5 g/L of Cu+2, 80 g/L of Cl−, 10 g/L of H2SO4, and variable concentrations of ferric and ferrous ions (0 and 2 g/L). The best copper extraction of 80.2% was found considering a pretreatment of 30 days, 25 kg/t of H2SO4, 50 kg/t of NaCl, and a leaching solution concentration described previously with 2 g/L of Fe+2. The results showed the leaching of all copper oxide species and 20% of the copper sulfide species. In addition, there was a reduction in the acid consumption as the resting time increases. Furthermore, to evaluate a possible decrease in time and acid in pretreatment and chloride in leaching, tests including 10 and 25 kg/t of H2SO4 and 1, 15, and 30 days of curing and a diminution of the NaCl concentration to 20 g/L (content from seawater) were executed. The results showed a significant effect on curing time below 15 days. Furthermore, the slight influence of the decrease of acid on copper extraction gives cost reduction opportunities. The diminution of chloride concentration (80 to 20 g/L) in leaching solution decreases the extraction from 79% to 66.5%. Finally, the Mellado leaching kinetic model was successfully implemented.

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