The role of chloride ions in metal sulfides leaching has been well established by researchers, the complexation of chloride ions was considered to be the main effect of chloride ions. In this work, the complexation of chloride ions was neglected by addition of EDTA, a strong complexing agent. In this way, further study was conducted on the effect of chloride ions. The increase of chloride ions concentration from 0 to 2 mol/L, decreased the open circuit potential of pyrite from 264 to 91 m V. Unless otherwise stated, all potentials in this paper are based on the potential of saturated calomel electrode. At 600 m V, the increase of chloride ions concentration acceleraed pyrite oxidation; at 800 and 1000 m V, however, the increase of chloride ions concentration lowered pyrite oxidation rate, and the proportion of elemental sulfur was also decreased with increasing chloride ions concentration; when chloride ions concentration increased from 0 to 2 mol/L, the proportion of elemental sulfur decreased from 32% to 28.4% at 800 m V, and 7.1% to 2.4% at 1000 m V.
