Pyrite arsenopyrite separation from

The adsorption of collectors on sulfide mineral occurs by two separate mechanisms chemical and electrochemical. The former results in the presence of chemisorbed metal xanthate (or other thiol collector ion) onto the mineral surface. The latter yields an oxidation product (dixanthogen if collector added is xanthate) that is the hydrophobic species adsorbed onto the mineral surface. The chemisorption mechanism is reported to occur with galena, chalcocite and sphalerite minerals, whereas electrochemical oxidation is reportedly the primary mechanism for pyrite, arsenopyrite, and pyrrhotite minerals. The mineral, chalcopyrite, is an example where both the mechanisms are known to be operative. Besides these mechanisms, the adsorption of collectors can be explained from the point of interfacial energies involved between air, mineral, and solution. 

Figure 17.5 Effect of temperature on separation of pyrite and arsenopyrite from a bulk pyrite/ arsenopyrite concentrate.

Separation of arsenopyrite and pyrite is important from the point of view of reducing downstream processing costs. Normally, roasting or pressure oxidation followed by cya-nidation is used to recover gold. 

The results in Table 10.8 show that the selective separation of galena from pyrite may be accomplished in alkaline medium and reducing potential. For the 1 1 mixture of galena and pyrite, the floated product assayed 76.31% Pb with a recovery of 90% at pH= 10.5 and potential -210 mV. Similar results can be achieved for the flotation separation of a mixture of galena and arsenopyrite as shown in Table 10.9. The floated product assayed 74.36% Pb with a recovery of 92% at pH = 9.5 and potential -300 mV. 

M. N. Chandraprabha, K. A. Natarajan, and R Somasundaran, Selective separation of pyrite from chalcopyrite and arsenopyrite by biomodulation using Acidithiobacillus fer-rooxidans, Internal. J. Mineral Processing 75(1-2) (2005). 

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