Cobalt extraction and concentration from manganese wad by leaching and precipitation

Abstract

Manganese wad often contains significant amounts of nickel, cobalt and copper, and it may represent a future source of these metals. The mineralogy and extractive metallurgy of a number of Australian wads are being examined with regard to producing a high-grade non-ferrous metal sulphide suitable for further processing. This paper describes the general approach taken, and some specific results obtained when a cobalt-rich wad from Queensland was leached with sulphur dioxide. The rate of dissolution is affected by the feed composition, particle size and sulphur dioxide flowrate. Under the conditions used, > 90% Co, Cu and Ni extraction is achieved in about 8 h. The Co, Cu and Ni can be readily precipitated from the clarified leachate by injection of hydrogen sulphide. The product contains about 60% (Co + Cu + Ni) with less than 0.1% Mn. As leaching is non-selective with respect to manganese, it will probably be necessary to recover and recycle the sulphur dioxide associated with the dissolved manganese when the ground wad is processed on a commercial scale.