LAUSR

Abstract The addition of ethylenediaminetetraacetic acid (EDTA) to a 1 M H2O2 leaching solution with low concentrations of sulfuric acid (0.007 M) and ethylene glycol (EG) (0.1 M) promotes significant increases of copper and iron leached from chalcopyrite. However, copper purification by solvent extraction is not possible due to the elevated stability of copper-EDTA and iron-EDTA complexes in the resulting leach liquor. Therefore, a two-stage process is presented that enables copper and iron dissolution at ambient temperature and pressure (26 °C and 101.325 kPa, respectively), without the necessity of solvent extraction. The proposed process uses the H2SO4-H2O2-ethylene glycol leaching solution in combination with organic ligands (oxalic acid (OxA) or EDTA). The first stage, using the leaching solution with oxalic acid, dissolved 29.5% of iron and transformed 49% of the copper to an oxalate salt; while in the second stage, the H2SO4-H2O2-ethylene glycol-EDTA leaching solution favored both the rapid dissolution of the copper oxalate salt and the chalcopyrite that did not react in the first stage. In this manner, the pregnant leach solution (PLS) from the second stage contained 90% and 35% of the total copper and iron, respectively, which may be electrowon directly. These results showed that the use of organic ligands promotes the formation of copper and iron complexes which help to delay, but not to avoid the decomposition of hydrogen peroxide due to a Fenton reaction and therefore, this results in an increase of the percentages of copper and iron leached, which permits processing at higher pulp density (50 g/L).