Mineralogical characteristics and oxygen pressure acid leaching process of copper smelting slag

By means of artificial heavy sand analysis, electron microscopy and electron probe analysis, chemical analysis, XRD, SEM and DES, the mineralogy of copper smelting slag was studied. The results show that copper bearing minerals in copper slag mainly exist in the form of matte, the iron bearing minerals mainly exist in the form of magnetite, gangue minerals mainly exist in the form of fayalite. Copper and iron in the slag are inlaid with each other and evenly distributed, and many minerals are wrapped with each other, so it is difficult to use them directly. Under the condition of pressure oxygen and low acidity, the leaching process can destroy the structure of copper and iron, extract copper efficiently and selectively, transform and reconstruct the iron and silicon in the slag into hematite and amorphous silica, respectively. Under the conditions of sulfuric acid concentration of 0.4 mol/L, reaction temperature of 200℃, liquid-solid ratio of 6 mL/g, oxygen partial pressure of 600 kPa, leaching time of 80 min and particle size of 75-150 μm, the leaching rates of Cu, Fe and Si from copper smelting slag are more than 95.0%, less than 0.6% and less than 2.0%, respectively, and the filtration rate of leaching slurry can reach 378.54 L/(m2∙h). Moreover, the iron and silicon in the leached slag are in the form of hematite (α-Fe2O3) and amorphous SiO2, respectively, and the copper content is less than 0.1% (mass fraction). © 2021, Science Press. All right reserved.