|
The oxide minerals of copper, lead, and zinc are frequently found associated with the sulfides of these metals. Where sufficient “oxide” copper or lead is present, it is usually recovered by flotation with xanthate following sulfidization with sodium sulfide OR NaHS. The flotation concentration is therefore more of a sulfide than a non-sulfide mineral flotation.
The mineral cuprite, azurite, malachite, and cerrussite will sulfidize readily with nominal amounts of sodium sulfide (1-10 lbs per ton of ore) – especially in those ores containing little or no iron oxides. Before sulfidizing, any sulfides present in the ore should be recovered. The addition of soda ash to precipitate calcium, iron, and zinc salts frequently reduces sodium sulfide requirements. Lime should be avoided as it hinders sulfidization. The addition of small amounts of copper sulfate usually aids activation of both sodium sulfide and xanthate is the preferred procedure.
In the absence of excessive iron oxides, it is also possible to sulfidize and float chrysocolla (CuSiO3) and anglesite (PbSO4). Some trouble may be encountered with the copper silicate if, as frequently happens, it is low grade. In these cases, the mineral is properly regarded as copper-bearing silica, and as such is difficult to concentrate.
However, the higher-grade copper silicates can be sulfidized and floated with good recovery from certain ores.
Fatty acids are sometimes used in conjunction with xanthates in the flotation of copper carbonates, but are of no value for copper silicates.
Other methods in which copper oxides are first leached with sulfuric acid, precipitated with sponge or scrap iron – or calcium sulfide – and then floated, have been described in the literature.
|
