Institut za rudarstvo i metalurgiju Bor

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COMMITTEE OF UNDERGROUND EXPLOITATION OF YU ISSN: 1451-0162 THE MINERAL DEPOSITS UDK: 622 UDK: 66.061:546.57(045)=20 Radojka Jonović * , Ljiljana Avramović * , Radmila Marković * SILVER LEACHING FROM SULPHIDE CONCENTRATE FROM THE „RUDNIK” MINE ** Abstract This work presents the results of laboratory investigations of hydrometallurgical method for non-ferrous and silver recovery from sulphide concentrate from mine "Rudnik". The unconventional method, developed in the Mining and Metallurgy Institute Bor – the low temperature sulphidation for degradation of sulphide forms of metals and transfer ion to oxide forms easy disoluble in water, was used for treatment the sulphide concentrate. Tne results of copper, zink and iron, leached with water after the sulphidation process, showed that the percentage of leaching for all elements was above 95 %. This method has shown the good results regarding to the basic requirement – total degradation of present sulphides, and also the important savings regarding to widely used oxidation roasting of sulphide concentrates. Next stage was cyanide leaching of silver with leaching percentage of 71.8 % Ag. Method of direct Ag leaching from sulphide concentrate with tiouree as the leaching reagent was also investigated. The leaching degree of Ag was 47.4 % Ag. Key words: sulphide concentrate, cyanide leaching, silver, tiourea INTRODUCTION The treatment of sulphide concentrate is characteristic that the precious metals particles were inserted into sulphides, more often in pyrite. First stage in complex treatment of sulphide concentrates is sulphide destruction for the aim of release the inserted gold and silver particles and, by this way, preparation for hydrometallurgical separation of precious metals and other non-ferrous metals. The following processes are used as the first technological stage: • Oxidation roasting • Autoclave leaching • Oxidation – chlorination method • High temperature chlorination • Nitro method • Bacterial leaching Second technological stage is precious metals recovery by leaching. Selection of dissolvent depends on precious metals content in concentrate as well as the other economical and ecological requirements. For over 100 years, cyanide has been the * Mining and Metallurgy Institute Bor ** This work is derived from the Project TR: 19002 financed by the Ministry of Science and Technological Development of the Republic of Serbia. No 1,2010. 85 MINING ENGINEERING
leaching reagents in the gold mining because of its high gold and silver recoveries and relatively low costs of process [1]. And today, over 100 years later [2], gold and silver are recovered using the cyanide simple reactions 1 and 2: 4Au+8NaCN+O2+2H2O= =4Na[Au(CN)2] +4NaOH..............(1) 4Ag+8NaCN+O2+2H2O= =4Na[Ag(CN)2] +4NaOH.............(2) Most cyanide leaching is carried out at an alkaline pH between 10 and 11, depending on individual concentrate characteristics [3]. Concentration of cyanide solution is also important in the leaching process with concentration of NaCN ranging from 0.02% to 0.15%. Concentration of sodium cyanide depends on precious metals content and other ingredients, first of all copper in sulphide concentrate. Oxidant [4], first of all oxygen, has also an important role in the leaching process of precious metals in cyanide solution. It has been proven that the dissolution rate of precious metals in cyanide solution is directly proportional to the amount of present oxygen. Mineralogical identification of concentrate is used for defining the technological flow sheet for concentrate [5]. Some alternative leaching agents, namely thiourea, have been tried due to the environmental concerns, generally without economic success [6]. EXPERIMENTS Characterization of Raw Materials and Treatment Methods Investigations were carried out on sulphide concentrate samples from the mine "RUDNIK". Chemical analysis of concentrate is given in Table 1. Table 1. Chemical analysis of concentrate Element Content, % Cu 18.04 Fe 24.51 Pb 7.45 Zn 12.04 Bi 0.47 Ag (g/t) 895 According to the carried out X-ray – structural analysis, the stage content of concentrate is the following: ZnS, FeS2, SiO2, PbS, CuFeS2. For separation of non-ferrous and precious metals from concentrate, the following technological methods were used: • Low temperature sulphatization for the aim of transfer the sulphide forms of metal into oxide forms • Leaching of sulphatization products with water for the aim of copper, iron and zinc transfer into solution • Cyanide leaching of Ag from sulphatization product after the recovery of non-ferrous metals. • Thiourea leaching of Ag from untreated concentrate. Investigations were carried out with 100 g of concentrate per experiment. Tube furnace for annealing was used in investigation as well as the glass laboratory reactor with heating lining and stirrer and heater with automatic temperature regulation, holes for charging and oxygen supply, and the other necessary laboratory equipment. RESULTS AND DISCUSSION Low Temperature Sulphatization Process Low temperature sulphatization process was carried out with the concentrated sulphuric acid. By leaching with water, after sulphatization, the following leaching degree was realized (Table 2): No 1,2010. 86 MINING ENGINEERING
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INSTITUT ZA RUDARSTVO I METALURGIJU
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KOMITET ZA PODZEMNU EKSPLOATACIJU Y
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Analizirajući ovaj način uzorkova
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SADRŽINA UPROŠĆENOG RUDARSKOG PR
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COMMITTEE OF UNDERGROUND EXPLOITATI
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area is constantly increased. Figur
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CONTENT OF THE SIMPLIFIED MINING PR
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U morfološkom smislu, teren predst
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Rezultati terenski istraživanja i
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In morphological terms, the terrain
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GEO-MECHANICAL FEATURES OF THE TERR
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Sl. 3. Smičući naponi u konstrukc
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Na modelu bojom su razgraničeni od
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Figure 3. Shear stresses in collect
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Page 114 and 115: Dry concentrate t 5,226 10.563 5.82
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da zaštiti podzemne vode od kontam
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• Otpadne vode od samog postrojen
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Practically, the “in-situ” expl
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• Waste water created during the
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geotektonska zona prema severoistok
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Osmatrani režim izdašnosti i temp
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Sl. 4. Kružni dijagram hemijskog s
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15. Nikl (Ni) 0,012±0,00500 UP-919
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alneoterapijskih i sportsko-rekreat
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phase are presented by andesite bas
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Figure 1. Hydro-geology maps of the
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Spring 2 Figure 3. Circle diagram o
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12. Lead (Pb)
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ecreational activities. The beginni
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UTICAJ GRANULOMETRIJSKOG SASTAVA ML
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SADR@AJ CONTENS D. Sokolović, D. E
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Institut za rudarstvo i metalurgiju Bor

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