Investigation of Copper Ammonia Leaching from Smelter Slags: Characterization, Leaching and Kinetics
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PROXIMATELY 80 pct of the primary copper in the world comes from low-grade or poor sulfide ores, which are usually treated by pyrometallurgical methods. Smelting sulfide ore concentrates produces two immiscible molten phases: a heavier sulfide phase containing most of the copper, the matte, and an oxide phase, the slag. It was revealed from phase analysis studies that the most commonly reported primary phases in nonferrous slag are olivine-group phases with the formula (Ca, Fe, Mg, Mn)2SiO4, and the most frequently reported phase with this formula is fayalite due to the Fe-rich nature of these slags. The next most commonly reported phases in non-ferrous slags are of the spinel group, particularly magnetite.[1] Although the chemical composition of copper slags varies with the types of furnace or process of treatment but its typical composition can be given as below[2]:
EHSAN BIDARI, Researcher, and VALEH AGHAZADEH, Assistant Professor, are with the Department of Mineral Processing, Faculty of Mining Engineering, Sahand University of Technology, Tabriz, Iran. Contact e-mail: [email protected], [email protected] Manuscript submitted November 3, 2014. METALLURGICAL AND MATERIALS TRANSACTIONS B
Fe: 30 to 40 pct, SiO2 : 35 to 40 pct, Al2 O3 : 0 to 10 pct, CaO: 0 to10 pct, Cu: 0:5 to 2:1 pct Subsequently, copper slags could be considered as an important secondary resource of copper. On the other hand, huge quantities of dumped slags result in wasting base metal values and cause environmental pollution due to the oxidation of entrained sulfur to sulfuric acid promoting slow leaching of heavy metals.[3] Therefore, extraction of base metal values from slags presents both economic and environmental incentives. Several methods for metal extraction from copper slag were reported. Basically, they can be classified into three categories, namely flotation, leaching, and roasting.[2] From the mineralogy of the copper-bearing phases in copper slags, it can be concluded that conventional sulfide flotation seems be the most appropriate method to beneficiate the copper slags. However, copper losses relating to the fine particle size fraction, existence of copper oxides, and elemental copper have been reported, and grinding to
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