ELECTROCHEMICAL OXIDATION OF PYRITE IN ALKALINE ELECTROLYTES: AN INVESTIGATION EMPLOYING CYCLIC VOLTAMMETRY, IN SITU SCANNING PROBE MICROSCOPY AND EX SITU X-RAY PHOTOELECTRON SPECTROSCOPY

摘要

The behaviour of pyrite in alkaline Ca(OH)_2-bearing electrolytes was investigated by voltammetry, X-ray photoelectron spectroscopy and in situ atomic force microscopy (AFM). Electrochemical oxidation of pyrite in alkaline electrolytes resulted in the formation of an oxygen-bearing surface product layer, voltammograms exhibiting pH-dependent cathodic currents due to the reduction of ferric (hydr)oxide. X-ray photoelectron spectroscopy (XPS) revealed that the iron within this alteration layer occupied an environment similar to that in hydrated ferric (hydr)oxides, whilst data for 5 suggested that elemental sulfur and/or polysulfides were the predominant S-bearing phases at the oxidised surface. In situ AFM imaging of the pyrite surface indicated extensive surface roughening and provided insight into the rate and spatial variation of the island growth of the oxidised product layer.