An in situ chronoamperometry/synchrotron radiation grazing incidence X-ray diffraction study of the electrochemical oxidation of pyrite in chloride media

Abstract

The influence of chloride on the electrochemical oxidation of pyrite has been studied using a combination of chronoamperometry (CA) and in situ synchrotron radiation grazing incidence X-ray diffraction (SR-GIXRD). The SR-GIXRD data revealed that the electrochemical oxidation of pyrite at 0.4 V vs. a psuedo stainless steel reference electrode induced the formation of crystalline FeSO 4, Fe(OH)SO 4 · 2H 2O and Fe(OH) 2 with an almost total extinction of the underlying pyrite. Similar patterns of oxidation were observed at 0.5 and 0.6 V vs. a pseudo stainless steel reference electrode; however, there was little or no oxidation products evident at 0.7 and 0.8 V vs. a pseudo stainless steel reference electrode. Significantly, in all cases, there was a significant build up in the quantity of amorphous reaction products, as evidenced by an elevation in intensity of the amorphous bump at low 2-theta, and this observation was supported by the visual appearance of the oxidised electrode at 0.7 and 0.8 V vs the pseudo stainless steel reference electrode which showed a “fools gold” appearance. These CA/SR-GIXRD outcomes suggest that oxidation of pyrite in chloride media under alkaline conditions may mildly passivate the electrode, and this may have important ramifications for the processing of pyritic ores in the hydrometallurgical industry.