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As the second largest solid waste in aluminum industry after red mud, the spent cathode carbon block has significant potential pollution hazards to the ecological environment, and is rich in a large number of high-quality graphite resources, with recycling properties. In order to realize the efficient recycling of high-quality graphite resources of spent cathode carbon block, the spent cathode carbon block was treated by high pressure leaching. The differences of physical and chemical properties of spent cathode carbon block, calcined petroleum coke and recovered graphite at different stages were systematically compared, and the recovered graphite was selected and blended with calcined petroleum coke to prepare the aluminum electrolytic carbon anode. The results show that compared with the calcined petroleum coke, the recovered graphite has similar industrial composition, phase composition and element content, but there are significant differences in crystal structure and asphalt wettability. In view of this, the performance of prepared anodes drops gradually with the increase of the amount of recycled graphite. Under the condition of low content, the recycled graphite from spent cathode carbon blocks has the feasibility and application potential of mixing and preparing aluminum electrolytic carbon anode. [ABSTRACT FROM AUTHOR]

In pursuit of carbon neutrality, the demand for metals that are necessary for the development of clean energy technologies is rapidly increasing. Metallurgical waste, such as slag, presents a promising secondary source of these key metals. This research aims to develop an eco-friendly hydrometallurgical process to recover Cu, Ni, and Co from discarded copper/nickel slag. High-pressure acid leaching (HPAL) was used to selectively leach Ni, Cu, and Co from the fayalite slag, yielding high leaching efficiencies of 99.9%, 89.4%, and 99.9%, respectively, with low Fe and Si tenors to the pregnant leach solution (PLS). The solvent extraction (SX) technique utilizing LIX 984N was used to selectively extract and enrich copper from the dilute PLS to about 23 g/L Cu with a very low Fe concentration of 0.05 g/L. Potassium amyl xanthate (PAX) solution was used to form Ni and Co xanthate complexes from the raffinate solution. Nickel was selectively recovered using ammonia solution, while the cobalt xanthate complex was thermally decomposed and recovered as cobalt oxide solids of about 25 wt.% Co. A comprehensive process flowsheet is presented. Furthermore, to realize the real application of the developed slag cleaning process, a preliminary economic evaluation was performed. [ABSTRACT FROM AUTHOR]

The processing of high-impurity ores has become increasingly common in recent years. Enargite (Cu 3 AsS 4) is an important source of copper, but it is notorious for its high arsenic content, posing serious environmental concerns. This study explores the potential of a high-pressure leaching system for treating high-arsenic-containing copper ores. The leaching behavior of enargite was studied to elucidate the role of ferric sulfate and NaCl in enhancing the dissolution of enargite and the fixation of As in the residue. Under optimized leaching conditions of 160 °C, 1.0 MPa, 0.1 mol/L Fe 2 (SO 4) 3 , and 0.34 mol/L NaCl, excellent copper extractions (97 %) and immobilization of arsenic (98 %) was achieved. The Fe/As ratio in the feed significantly influenced arsenic removal minerals, with lower ratios of less than 1 favoring scorodite precipitation, while higher ratios (Fe/As > 1) promoted arsenic removal through sorption and co-precipitation with natrojarosite. Sodium chloride addition enhanced natrojarosite precipitation, reducing the total dissolved iron in the leachate. Arsenic attenuation onto jarosite was found to be difficult to form in the absence of NaCl and was more effective with mixed minerals (enargite, chalcopyrite, and pyrite) as opposed to only enargite. A relationship was established between Fe and free acidity in the leachate when NaCl was used, with a correlation coefficient of 0.992. Additionally, a correlation coefficient of 0.921 was obtained between final Fe and As concentrations in the leachate suggesting that As tenors can be managed by controlling free acidity. Evaluation of the environmental stability of the leach residue using the TCLP test showed an As leachability of 5.84 mg/L. [Display omitted] • High-pressure leaching yielded 97 % Cu extractions and fixed 98 % As as scorodite. • The role of added Na+ and Cl- ions in the leaching process was revealed. • High pyrite content can act as a major oxidant and catalyst for enargite leaching. • The relationship between As, Fe, and free acidity in the leachate was established. • Environmental stability of leach residues for As elution was conducted. [ABSTRACT FROM AUTHOR]

The flotation tailings obtained from Bor Copper Mine contain pyrite (FeS2) and chalcopyrite (CuFeS2), these sulfide minerals are known to promote acid mine drainage (AMD) which poses a serious threat to the environment and human health. This study focuses on the treatment of mine tailings to convert the AMD supporting minerals to more stable forms, while simultaneously valorizing the mine tailings. A combination of hydrometallurgical processes of high-pressure oxidative leaching (HPOL), solvent extraction (SX), and electrowinning (EW) were utilized to recover copper from mine tailings which contain about 0.3% Cu content. The HPOL process yielded a high copper leaching rate of 94.4% when water was used as a leaching medium. The copper leaching kinetics were promoted by the generation of sulfuric acid due to pyrite oxidation. It was also confirmed that a low iron concentration (1.4 g/L) and a high copper concentration (44.8 g/L) obtained in the stripped solution resulted in an improved copper electrodeposition current efficiency during copper electrowinning. Moreover, pyrite, which is primarily in the mine tailings, was converted into hematite after HPOL. A stability evaluation of the solid residue confirmed almost no elution of metal ions, confirming the reduced environmental loading of mine tailings through re-processing.

Ammonia leaching is a promising method for processing low-grade copper ores, especially those containing large amounts of oxidized copper. In this paper, we study the effect of Si-containing minerals on the kinetics of Cu and Ag leaching from low-grade copper concentrates. The results of experiments on the pressure leaching of the initial copper concentrate in an ammonium/ammonium-carbonate solution with oxygen as an oxidizing agent are in good agreement with the shrinking core model in the intra-diffusion mode: in this case, the activation energies were 53.50 kJ/mol for Cu and 90.35 kJ/mol for Ag. Energy-dispersive X-ray spectroscopy analysis (EDX) analysis showed that reagent diffusion to Cu-bearing minerals can be limited by aluminosilicate minerals of the gangue. The recovery rate for copper and silver increases significantly after a preliminary alkaline desilication of the concentrate, and the new shrinking core model is the most adequate, showing that the process is limited by diffusion through the product layer and interfacial diffusion. The activation energy of the process increases to 86.76 kJ/mol for Cu and 92.15 kJ/mol for Ag. Using the time-to-a-given-fraction method, it has been shown that a high activation energy is required in the later stages of the process, when the most resistant sulfide minerals of copper and silver apparently remain.

Sulfide copper mineral, typically Chalcopyrite (CuFeS 2 ), is one of the most common minerals for producing metallic copper via the pyrometallurgical process. Generally, flotation tailings are produced as a byproduct of flotation and still consist of un‒recovered copper. In addition, it is expected that more tailings will be produced in the coming years due to the increased exploration of low‒grade copper ores. Therefore, this research aims to develop a copper recovery process from flotation tailings using high‒pressure leaching (HPL) followed by solvent extraction. Over 94.4% copper was dissolved from the sample (CuFeS 2 as main copper mineral) by HPL in a H 2 O media in the presence of pyrite, whereas the iron was co‒dissolved with copper according to an equation given as C Cu  = 38.40 ×  C Fe . To avoid co‒dissolved iron giving a negative effect on the subsequent process of electrowinning, solvent extraction was conducted on the pregnant leach solution for improving copper concentration. The result showed that 91.3% copper was recovered in a stripped solution and 98.6% iron was removed under the optimal extraction conditions. As a result, 86.2% of copper was recovered from the concentrate of flotation tailings by a proposed HPL‒solvent extraction process. [ABSTRACT FROM AUTHOR]

[Display omitted] • High-pressure oxidative acid leaching on carbonaceous sulfide ore was investigated. • Optimized leaching parameters yielded over 97% copper extraction from the ore. • Selective dissolution of copper over iron is achieved when free acidity is ≈10 g/L. • A linear relation between log[Fe] and log[free acidity] in the PLS was established. • Over 99% copper was precipitated from the PLS by NaSH addition. The increase of impurities and complexity of copper ores are among the recent challenges in the mining industry. Complex carbonaceous sulfide ores are extremely difficult to treat due to their mineralogical complexity and impurities of organic carbon and carbonates. This study focuses on the development of a hydrometallurgical process for efficient copper extraction from complex carbonaceous sulfide ore which contains chalcopyrite, carbonates (dolomite and calcite), and carbonaceous gangue minerals. Characterization of the ore sample and leach residues was conducted using XRD and EPMA analysis, while ICP-OES was used for the determination of total dissolved metals in solution. High-pressure leaching of complex carbonaceous sulfide ore in oxygenated sulfuric acid solution was performed and the influence of leaching parameters such as sulfuric acid concentration, temperature, total pressure, and pulp density was studied. The extraction of copper increased with increasing temperature, sulfuric acid concentration, and total pressure. On the other hand, an increase in pulp density resulted in a decline in copper extraction due to an increased slurry viscosity and resistance in the diffusive mass transfer of reactants. Selective dissolution of copper from iron can be achieved by controlling free acidity in the pregnant leach solution (PLS). Under these leaching conditions: 100 g/L, 1 M H 2 SO 4 , 160 °C, 1.0 MPa total pressure, the highest copper and iron extractions achieved were 97.55% and 95.37%, respectively. Precipitation of copper from the PLS by NaSH sulfidization was investigated and more than 99.9% of copper was recovered at a Cu: NaSH molar ratio of 1:1.8. [ABSTRACT FROM AUTHOR]

The flotation tailings obtained from Bor Copper Mine contain pyrite (FeS2) and chalcopyrite (CuFeS2), these sulfide minerals are known to promote acid mine drainage (AMD) which poses a serious threat to the environment and human health. This study focuses on the treatment of mine tailings to convert the AMD supporting minerals to more stable forms, while simultaneously valorizing the mine tailings. A combination of hydrometallurgical processes of high-pressure oxidative leaching (HPOL), solvent extraction (SX), and electrowinning (EW) were utilized to recover copper from mine tailings which contain about 0.3% Cu content. The HPOL process yielded a high copper leaching rate of 94.4% when water was used as a leaching medium. The copper leaching kinetics were promoted by the generation of sulfuric acid due to pyrite oxidation. It was also confirmed that a low iron concentration (1.4 g/L) and a high copper concentration (44.8 g/L) obtained in the stripped solution resulted in an improved copper electrodeposition current efficiency during copper electrowinning. Moreover, pyrite, which is primarily in the mine tailings, was converted into hematite after HPOL. A stability evaluation of the solid residue confirmed almost no elution of metal ions, confirming the reduced environmental loading of mine tailings through re-processing. [ABSTRACT FROM AUTHOR]

Ammonia leaching is a promising method for processing low-grade copper ores, especially those containing large amounts of oxidized copper. In this paper, we study the effect of Si-containing minerals on the kinetics of Cu and Ag leaching from low-grade copper concentrates. The results of experiments on the pressure leaching of the initial copper concentrate in an ammonium/ammonium-carbonate solution with oxygen as an oxidizing agent are in good agreement with the shrinking core model in the intra-diffusion mode: in this case, the activation energies were 53.50 kJ/mol for Cu and 90.35 kJ/mol for Ag. Energy-dispersive X-ray spectroscopy analysis (EDX) analysis showed that reagent diffusion to Cu-bearing minerals can be limited by aluminosilicate minerals of the gangue. The recovery rate for copper and silver increases significantly after a preliminary alkaline desilication of the concentrate, and the new shrinking core model is the most adequate, showing that the process is limited by diffusion through the product layer and interfacial diffusion. The activation energy of the process increases to 86.76 kJ/mol for Cu and 92.15 kJ/mol for Ag. Using the time-to-a-given-fraction method, it has been shown that a high activation energy is required in the later stages of the process, when the most resistant sulfide minerals of copper and silver apparently remain. [ABSTRACT FROM AUTHOR]