China Nonferrous Metallurgy

To address the problems of low leaching efficiency and poor adaptability of existing processes for lowgrade complex copper sulfide tailings， this study adopts ethylene thiourea （ETU） synergistically with microorganisms for leaching flotation tailings from an overseas enterprise in a ferric sulfate system. The effects of ETU concentration， leaching time， and pulp density on copper leaching efficiency were systematically investigated， along with the decomposition law of ETU and treatment methods for its residues， aiming to eliminate interference with subsequent solvent extraction-electrowinning （SX-EW） processes. The results show that the copper leaching efficiency increases with the rise of ETU concentration and extension of leaching time， while decreasing with the increase of pulp density. Under the optimal conditions （ETU concentration of 200 mg/L， pulp density of 20%， pH=1. 5， and leaching at room temperature for 72 h）， the copper leaching efficiency reaches 87. 32%. Fe3?， Cu2?， and aeration can accelerate ETU decomposition， whereas an acidic environment and sodium hexametaphosphate can stabilize ETU. Residual ETU in the leachate reduces the copper extraction rate from 95% to 38% and causes nodulation on electrodeposited cathode copper. Complete removal of ETU and elimination of its impact on subsequent processes can be achieved through aeration treatment. This study provides key process parameters and technical support for the efficient treatment of similar complex copper sulfide tailings.