Leaching of Chalcopyrite Concentrate with Hydrogen Peroxide and Sulfuric Acid in an Autoclave System
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NTRODUCTION
COPPER is most commonly present in the earth’s crust as copper-iron-sulfide and copper sulfide minerals, e.g., chalcopyrite (CuFeS2), bornite (Cu5FeS4), and chalcocite (Cu2S). Typical copper ores contain from 0.5 pct Cu (open pit mines) to 1 or 2 pct Cu (underground mines). Chalcopyrite contains the least copper compared with the others. On the other hand, chalcopyrite is the most important one due to the most abundant sulphidic copper-bearing mineral.[1,2] Chalcopyrite is firstly enriched by flotation to separate it from the other sulfide minerals. The obtained chalcopyrite concentrate is treated by conventional pyrometallurgical processes that include melting-converting-refining-electrolyzing methods. During the pyrometallurgical processes of copper, SOx (SO2 and/or SO3) gases are emitted into the atmosphere and this emission causes some environmental problems. These gas emissions may also include toxic compounds of heavy metals. To overcome these environmental problems and to obtain some economical advantage, the use of the hydrometallurgical process for copper production seems appropriate as an alternative method because it has many advantages such as being eco-friendly, easy operation, low energy depletion, and low cost.[3] Chalcopyrite leaching studies in the literature M. DENIZ TURAN, Assistant Professor, is with the Department of Metallurgical and Materials Engineering, Firat University, 23119 Elazig˘, Turkey. Contact e-mail: mdturan@firat.edu.tr H. SONER ALTUNDOG˘AN, Professor, is with the Department of Bioengineering, Firat University, 23119 Elazig˘, Turkey. Manuscript submitted July 27, 2012. Article published online May 1, 2013. METALLURGICAL AND MATERIALS TRANSACTIONS B
can be classified as direct leaching of chalcopyrite using various oxidation agents,[4–13] leaching of chalcopyrite after the some pretreatments,[14–20] and bacteriological leaching.[21–24] Because chalcopyrite has a compact structure, strong oxidative conditions are required for decomposition of its mineral structure. For that reason, besides the strong oxidation agent, some effective leaching conditions such as high temperature and high pressure are required. Nevertheless, there are some problems concerning the low dissolution rates, copper losses, and disposal of the large amount of iron which dissolves along with the copper in the direct leaching of chalcopyrite.[20] Actually, oxygen gas is conventionally used in acidic leaching as an oxidant. In earlier studies, the use of some other oxidation agents was investigated instead of oxygen such as hydrogen peroxide,[2] ferric chloride,[7,8] dichromate,[12] and chlorine.[19] Studies have generally focused on the use of active oxygen-containing reagents as oxidants for leaching of sulfide minerals.[25–29] Among the aforementioned oxidants, hydrogen peroxide is a good oxidizing agent and can be used for copper leaching because its oxidation potential (1.77 V) is adequate for oxidizing almost all the metal sulfide. The oxidative action of hydrogen peroxide in acidic solution is based on it
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