Pyrite gold recovery

The minerals that influence gold recovery in these ores are iron sulphides (i.e. pyrite, marcasite, etc.), in which gold is usually associated as minute inclusions. Thus, the iron sulphide content of the ore determines gold recovery in the final concentrate. Figure 17.3 shows the relationship between pyrite content of the ore and gold recovery in the copper concentrate for two different ore types. Most of the gold losses occur in the pyrite. 

Figure 17.3 Effect of pyrite content of the ore on gold recovery in the copper-gold concentrate at 30% Cu concentrate grade (1 ore from Peru 2 ore from Indonesia).

A more recent development involves the use of chemolithotrophic bacteria to solubilize sulfidic material which interferes with the normal chemical extraction process for a particular metal. A striking example is that of gold in refractory sulfidic ores, such as pyrite or arse-nopyrite, where gold recovery on cyanidation may be as low as 10-15% of the total gold present. Bacterial pretreatment of the concentrate to oxidize and solubilize the sulfide leads to enhanced recoveries of gold on cyanidation, often close to 100% of the total (Section V). 

The Fairview Mine of Gencor in South Africa has operated a biooxidation plant since 1986. This accounts for about 40% of the pyrite/ arsenopyrite concentrate produced in the mine, taking about 12 tons per day. Gold recovery is greater than 95% after 4 days residence time. 

The flotation performance of isothiourea is influenced obviously by pulp pH. Isothiourea only performs in alkaline medium. For example, the effect of pH on the recovery rate of gold pyrite using amyl isothiourea as collector is shown in Fig. 1.5 [12]. 

Fig. 1.5 Effect of pH on the recovery rate of gold pyrite using amyl isothiourea as collectOT...

III) Mercapto-benzothiazole performs very strong coUecling capability toward the pyrites containing gold. It was reported that the recovery rate of gold is improved from 41.3-57.8 to 54.3-65.2 % in the flotation of Virginia pyrite. 

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