Study on Selective Leaching of Copper and Simultaneous Precipitation of Iron in Polymetallic Complex Chalcopyrite by Hydrothermal Leaching Under Oxygen Pressure

Due to the increasing complexity and dilution of copper resources, a large number of refractory polymetallic complex chalcopyrite are produced. In this study for resolving puzzle in oxygen pressure acid leaching of polymetallic complex chalcopyrite, such as prone to produce dangerous solid wastes like lead jarosite and high iron content in leaching solution, the technology of hydrothermal leaching under oxygen pressure without acid is proposed to extract copper efficiently and selectively and to precipitate iron by hematite process simultaneously. The results show that under the experimental conditions of initial sulfuric acid concentration of 0 g/L, reaction temperature of 200 °C, oxygen partial pressure of 1.2 MPa, liquid–solid ratio of 10 mL/g, sodium lignosulfonate addition of 0.5 pct mass of raw material, leaching time of 120 minutes, and stirring speed of 400 r/min, copper leaching rate can reach 99.86 pct. At this time, the iron content of leaching solution is only 4.3 g/L; Chalcopyrite (CuFeS 2 ), porphyrite (Cu 5 FeS 4 ), pyrite (FeS 2 ), galena (PbS), and other mineral phases can completely react in the system to form corresponding metal sulfate, and Fe 3+ is converted to hematite by directed hydrolysis, thus inhibiting the generation of dangerous solid waste such as lead jarosite.