Simultaneous removal of copper and nickel from a high-ferrous reductive leach solution using ferrous sulfide precipitation

Copper and nickel impurities in the reductive leach solution from oxygen-pressure leaching residue of high-nickel matte are detrimental to the subsequent recovery of iron. This study aims to remove copper and nickel from high-iron reductive leachate using FeS and recover them in the form of sulfides. To this end, based on the thermodynamic analysis of copper and nickel precipitation, as well as the dissolution conditions of FeS, the theoretical addition coefficient of FeS, reaction temperature, and reaction time were identified as key factors influencing the precipitation process. The study found that the precipitation rates of copper and nickel increased with decreasing solution pH and rising temperature. Under the conditions of 80°C, 2.4 times the theoretical FeS addition, and a reaction time of 80 min, the concentrations of copper and nickel in the high-iron reductive leachate were reduced to below 6 and 9 mg/L, respectively, demonstrating significant removal efficiency. The copper and nickel grades in the precipitate were 16% and 13%, respectively. These findings are expected to contribute to the recovery of iron resources from high-iron reductive leachate and the selective separation of copper and nickel, thus enhancing the economic value of resource recovery.