he sweeps in Fig. 10 were initiated in the negative direction at potential of −300 mV which was a little more negative than the open circuit potential. The first cycle reflects a freshly polished surface. The appearance of peak C1 in the first cycle indicates the formation of sulphur-rich sub-layer during electrode handling and preparation.
A potential window from −800 mV to 300 mV was selected to investigate the electrochemical behaviour of pyrite in xanthate and/or cyanide solution. The results using a second scan are illustrated in Fig. 11. For pyrite electrode in borate background solution as shown in Fig. 11(a), the peak C1 on the cathodic scan corresponding to the reduction of elemental sulphur to hydrosulphide ions (HS−) was also evident. However, peak A1 on the anodic scan also contained a contribution from the oxidation of hydrosulphide to elemental sulphur and its deposition on pyrite surface, represented by the reversal of Eq. (12). When pyrite was treated with PAX, a reaction occurred and resulted in a peak A2 on the anodic scan corresponding to the oxidation of xanthate to dixanthogen in Eq. (13).