Interest for application of hydrometallurgical processes in a processing of complex sulphide ores and concentrates has increased in recent years. Their application provides better metal recoveries and reduced emission of gaseous and toxic ageneses in the environment. The kinetics and mechanism of sphalerite leaching from complex sulphide concentrate with sulphuric acid and sodium nitrate solution at standard conditions was presented in this paper. The influences of temperature and time on the leaching degree of zinc were investigated and kinetic analysis of the process was accomplished. With temperature increasing from 60 to 90°C, the zinc leaching increased from 25.23% to 71.66% after 2 hours, i.e. from 59.40% to 99.83% after 4 hours. The selected kinetic model indicated that the diffusion through the product layer was the rate-controlling step during the sphalerite leaching. The activation energy was determined to be 55 kJ/mol in the temperature range 60-90°C. XRD, light microscopy and SEM/EDX analyses of the complex concentrate and leach residue confirmed formation of elemental sulphur and diffusion-controlled leaching mechanism
The copper mine Cerovo-East Serbia, as well as the other ore bodies in its vicinity, contains a significant amount of oxide copper minerals in their uper layers (>40%). Processing of such mixed ores by the existing concentration technologies leads to a substantial copper losses (<60%). Reduction of "oxide copper", by acid leaching prior the flotation concentration, can increase the overall copper efficiency up to more than 70% in the single-stage leaching, achieving an efficiency in the flotation concentration stage higher than 75%. Based on the performed experimental results, the flow sheet for processing of the mixed oxide-sulfide copper ore is proposed.
The investigation results of the processing possibilities of the complex barite‐sulphide ore from “Bobija” deposit (Serbia) for the sake of lead, zinc and copper extraction are presented in this paper. Through x‐ray diffraction and microscopic examination it is concluded that: (a) it is not possible to enrich the ore for obtaining any selective or a collective sulphide concentrate using the conventional methods of mineral processing, and (b) it is necessary to include chemical and technological procedures for ore processing. Examination of reduction roasting with carbon addition for the barite (BaSO4) reduction into good soluble BaS is performed. After water leaching of BaS from the calcined ore, the solid residual is submitted to the magnetic separation procedure for the pyrrhotite (Fex−1Sx) separation, which is formed after pyrite (FeS2) dissociation, and for obtaining a collective sulphide concentrate Pb–Zn–Cu. Finally, the sulphide concentrate is leached with the solution of H2SO4 in the presence of oxygen at elevated temperatures and pressures in an autoclave. Through their sulphide oxidation zinc, copper and iron were dissolved, while lead sulphide remained as insoluble in the solid residual after leaching. The influence of the working parameters on the degree of leaching of zinc, copper and iron is examined.
During the chalcopyrite leaching by sodium nitrate and sulfuric acid solution, leaching rate decreases with increasing the time and a part of chalcopyrite mineral grains remains in the leach residue. In chalcopyrite concentrate, 95.5 % of chalcopyrite mineral occurs as in liberated grains, and the rest is in association with gangue minerals, which is very favorably from the aspect of hydrometallurgical treatment. Complex forms, like impregnations and complex intergrowths, do not exist. After experiments carried out, leaching of copper achieved 84 % at temperature 80 o C and time 240 min. In the all leach residues, 97 % chalcopyrite mineral grains occur as liberated with highly corroded surfaces. Therefore, the structural assembly of chalcopyrite grains is favorable and no reason to reduce the leaching rate in the final stage of reaction. Reason for this is elemental sulfur, which was formed during the reaction, precipitated at the particle surfaces, and slowed down the leaching rate in the final stage of leaching process.
The results of research on the leaching process of complex sulphide-barite ore were presented in this paper. The leaching process was carried out in a laboratory autoclave by ferric chloride solution. Considering that those minerals are represented in complex structural-textural relationships, it is not possible to extract lead, zinc and copper minerals from ore by flotation methods. The obtained results confirmed possibility of the ore processing directly, by chemical methods. The effect of temperature, time and oxygen partial pressure on the lead, zinc and copper dissolution was studied. The maximal leaching degree was achieved at 100 C and amount of 91.5 % for Pb, 96.1 % for Zn and 60.7 % for Cu). Leaching at temperatures above 100 C is impractical.
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