Leaching of cuprite with ozone as an oxidant in sulfuric acid solution and its oxidation leaching mechanism

Abstract

Leaching has been an effective method for extracting copper from cuprite, but disproportionation reaction occurs in its acid leaching process and forms copper ions and copper elements, which results in the highest leaching rate available reaching only 50%. In this investigation, ozone was used to oxidize the cuprite to improve its leaching rate in a sulfuric acid solution, and its oxidation leaching mechanism was proposed and verified via various characterizations. The leaching test results indicated that when the temperature, acid concentrate and stirring speed were kept at constant of 50 °C, 0.014 mol/L, 800 rpm, respectively, the leaching rate of cuprite significantly increased by 43.24% with the increase of the ozone ventilation volume from 0 L/min to 3.0 L/min. Moreover, the leaching process of cuprite controlled by mixed steps and the reaction activation energy was 31.51 kJ/mol. The atomic force microscope observation revealed a noticeable alteration in the surface morphology of cuprite after oxidation leaching. The peak height experienced a significantly decrease, indicating that the oxidation leaching reaction was intensified. The analyses from the X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy-energy dispersive spectroscopy and time-of-flight secondary ion mass spectrometry indicated that copper elements formed during the direct leaching of cuprite due to the disproportionation reaction, while most Cu2O were dissolved during the oxidation leaching process. When ozone was added, the Cu + on the cuprite surface was oxidized to Cu2+, and each newly generated CuO film was timely dissolved in the sulfuric acid. It is thus concluded that ozone effectively oxidized cuprite, strengthened its leaching process, and significantly increased its leaching rate. The findings of this study might provide a green approach for the effective oxidation leaching of cuprite.