Two-stage hydrochloric leaching of oxidized nickel ore of the Serovsky deposit

Significant reserves of oxidized nickel ores are concentrated in the Ural region, in the deposits of various sizes that are mined by open-pit method. Ore is rather loose, which makes the cost of production relatively low. At the same time, the technologies employed at Ural nickel plants fail to meet the energy conservation requirements, and they are environmentally unfriendly and unprofitable. The paper proposes a two-stage hydrometallurgical technology for processing oxidized nickel ores from the Serovsky deposit. The composition of investigated ore is, wt.%: 1.01 Ni, 0.031 Co, 15.32 Fe total , 8.51 Al 2 O 3 , 21.76 MgO, 43.97 SiO 2 . The phase composition of the sample was determined by powder diffraction on the XRD-7000 X-ray diffractometer (Shimadzu, Japan). Serpentine Mg 6 [Ni, Si 4 O 10 ](OH) 8 and nimite (Ni, Mg, Al) 6 (Si, Al) 4 О 10 (OH) 8 were identified as the main nickel-containing minerals. Nickel enters the crystal lattice of silicates and replaces magnesium and iron isomorphically, which significantly complicates the disintegration of such minerals by the hydrometallurgical method. The paper provides the results of laboratory studies into atmospheric ore leaching with hydrochloric acid at the first stage and autoclave leaching of the obtained slurry at the second stage depending on temperature, leaching time and acid consumption. The total (in two stages) extraction into the solution was, wt.%: 82 Ni, 73.6 Co, 22 Fe, 22 Mg, 50.4 Al. Hydrochloric acid is almost completely consumed under these conditions with residual acid concentration of about 3 g/dm 3 . The autoclave slurry has good filterability. Cake composition after autoclave leaching is as follows, wt.%: 0.35 Ni, 0.01 Co, 12 Fe total , 10.63 Mg, 1.2 Al, 55 SiO 2 .