Selective leaching of a high-iron cobalt matte at atmospheric pressure

Selective leaching of high iron cobalt matte in sulfuric acid at atmospheric pressure is being reported. The matte assaying 4.55%Co, 13.58%Ni, 3.72%Cu and 53.6%Fe was produced by carbothermal reduction and pyrite sulfuration of nickel converter slag containing 1.36%Co, 3.39%Ni and 1.01%Cu from the Jinlong nickel smelter (Yunnan, China). The process is made up of three-step countercurrent leaching. In the first step most Fe of the matte is leached as the fresh matte is mixed with some sulfuric acid solution containing low concentrations of Co and Ni ions from the third step. The leach residue of the first step is contacted with the rest leachate of the third step leachate, and Co and Ni partially dissolve. The leach residue from the second leaching step is leached with 5.5 M sulfuric acid, the leachate is diluted and divided into two parts as the leachants to the first and second leaching step. In the first step, 71.6%Fe, 0.6%Co and 0.2%Ni dissolve and 99.0%Co and 99.5%Ni are extracted by injecting H2S; in contrast, 67.5%Fe, 3.5%Co and 0.4%Ni dissolve in the first step, and 96.1%Co and 99.2%Ni are extracted without H2S input.