Simulation of precious metals recovery from nickel smelter slag under high-pressure oxidative acid leaching (HPOXAL)

Abstract

The nickel smelter slag as a solid waste of pyrometallurgical operations can be harmful to the environment especially against the ground that will be contaminated by hazardous components contained the smelter slag. Nickel smelter slag has the content of valuable metals as the following: Nickel (Ni), Cobalt (Co), Copper (Cu), Iron (Fe) and Zinc (Zn). Those valuable metals were carried out by high-pressure oxidative acid leaching to recover all the valuable metals suitable with the high measures of recovery. High-pressure oxidative acid leaching (HPOXAL) is a suitable process for the nickel smelter slag with the parameters of the leaching process as the following: the particle size about – 150 + 74 μm, sulfuric acid solution with the concentration of 0.3 mol in 1 liter solution, Ratio of Liquid to Solid (L/S) with 7 ml of liquid to 1 gram of solid components, oxygen overpressure at 600 kPa, operating temperature about 180 - 200 °C and the retention time of 80 minutes. The measures recovery of this leaching process for each valuable metal in percent of initial weight such as nickel and cobalt about 97%, copper about 95%, 94% of zinc and all iron can be separated, respectively. At the separation section, LIX 984N as extractant extracts copper from the product (leaching solution) of the reactor, limestone was used to capture iron in the leaching solution, versatic 10 and decyl-4PC were conducted to remove undesirable mineral that was generated from the leaching process, and cyanex 272 extractants to extract such as nickel, cobalt, and zinc, respectively. This simulation used the feed flowrate with 150 tons per day. The results of the precious metals product were generated each the mass rate such as copper, nickel, cobalt, zinc, and iron with 927 kg/day, 2147 kg/day, 875 kg/day, 199 kg/day and 71,000 kg/day, respectively.