Secondary copper minerals such as chalcocite (Cu_2S) and covellite (CuS) are known to dissolve in acidic ferric sulphate solutions. However, the quantities of ferric sulphate required to achieve acceptable recoveries for high-grade copper feeds are prohibitive, unless the resulting ferrous sulphate is reoxidized and reused. A plant recently commissioned in Australia employs an autoclave for that purpose. This paper describes a novel approach, called the "Regenerated Ferric Sulphate Leaching (RFSL) process, in which the reoxidation of the ferrous ion is carried out under strictly atmospheric conditions, using SO_2/O_2 mixtures as the oxidizing medium. The process is very effective and rapid, and the reoxidation step can be accomplished during the leach itself or in a separate vessel. Several examples are presented for ores and concentrates originating from the USA, Central America and South East Asia. The overall concept of the process is also briefly assessed with respect to the main operating costs and sulfur balance.
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