Catalytic-Oxidative Leaching of Low-Grade Complex Zinc Ore by Cu (II) Ions Produced from Copper Ore in Ammonia-Ammonium
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INTRODUCTION
THE exploitation of low-grade oxide copper/zinc ores and sulfide-oxide copper/zinc ores is increasingly important as mineral resources get more and more exhausted. However, the conventional beneficiation and metallurgy for these ores have been challenged owing to stricter environmental requirements in the world.[1–3] Hydrometallurgical methods have been developed and widely used in the extraction of copper, zinc, and nickel ores. The hydrometallurgical methods, such as pressure-ammonia leaching,[4] ammonia-oxygen leaching,[5,6] and chloride leaching,[7,8] have different advantages in processing these ores. Catalytic-oxidative leaching[9–16] is a new hydrometallurgical method to treat complex ores with sulfides. The catalytic action of Co(II),[12] Ag(I),[12–14] and Cu(II)[17,18] ions on the extraction of zinc from sphalerite at elevated temperature and oxygen pressure has been investigated. Ammonia, as an effective lixiviant, has been extensively used in hydrometallurgical processes for many years due to its inherent advantages over alternative reagents. The main advantage is that the basic leaching solution alleviates corrosion problems encountered in the acidic systems. Ammoniacal leaching minimizes the major wasteful components like iron, which can be removed as insoluble oxy/hydroxyl compounds during the leaching process. Ammonia leaching is used in copper, cobalt, and nickel ZHI XIONG LIU, Lecturer, is with the College of Chemistry and Chemical Engineering, Jishou University, Jishou City, Hunan Province 410083, P.R. China. Contact e-mail: [email protected] ZHOU LAN YIN, HUI PING HU, and QI YUAN CHEN, Scientists, are with the School of Chemistry and Chemical Engineering, Central South University, Changsha City, Hunan 410083, P.R. China. Manuscript submitted October 26, 2011. Article published online July 21, 2012. METALLURGICAL AND MATERIALS TRANSACTIONS B
industries[5,6,19–22] due to the formation of metal-ammonia complexes that are highly soluble in ammoniacal solution.[23] The extraction of metals from raffinate via solvent extraction (SX) has been studied intensively,[24,25] and the lixiviant can be recycled. Most oxidation reactions of sulfides in ammoniacal solution take place slowly in the presence of O2 or air at low temperature (below 323.15 K [50 °C]),[26] and hence, the oxidative leaching of sulfide ores in ammoniacal solution is generally processed under high pressure and temperature.[4–6,18,22] Tangdan oxide copper mine in Yunnan Province, which contains a high content of calcium-magnesium carbonate gangue and has poor floatation characteristics, is a large copper mine with a reserve of about 115 9 104 t. Its average grade of copper is 0.75 pct (mass fraction) and the phase distribution of copper is quite complex, including malachite, chrysocolla, and bornite.[27] Lanping oxide zinc mine in Yunnan Province is a large zinc ore with high-content silicon-calcium gangues and poor floatation characteristic, and its reserve is about 1289 9 104 t. Its average grade of zinc is 5.74 pct (mass fraction), a
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