Toxic heavy metal removal from sulfide ores using potassium permanganate: Process development and waste management

Abstract

A monolithic new attitude utilizing Aspen Plus software and Taguchi method has been applied to evaluate a novel configuration for removal of toxic heavy metals during sulfide ores recovery using potassium permanganate (KMnO4). In this new configuration, KMnO4 has been produced by sludge recovery of cobalt purification step containing manganese (IV) oxide (MnO2). Also, in this suggested configuration, the required sulfuric acid (H2SO4) solvent has been provided by recovery of sulfur compounds released during leaching process of sulfide ores. The optimum condition obtained by Taguchi experimental design has been used as initial data for the simulation and sensitivity analysis of process via Aspen Plus software. A systematic study of the design and operating condition has been made for key performance metrics such as removal of toxic heavy metal from sulfide ores, recovery of KMnO4 from sludge containing MnO2 and conversion of released sulfide gases to H2SO4 at the different operating condition such as H2SO4 concentration of 60–90 g/L, operating temperature of 60–150 °C, agitation rate of 100–400 rpm, reaction time of 0.5–2 h, solid to liquid ratio of 1:1–1:4, particle size of 10–500 μm, additive amount of 10–40 wt% and oxygen pressure of 0.5–2 MPa. The optimum condition for removal of toxic heavy metal have been found to be H2SO4 concentration of 70 g/L, temperature of 90 °C, agitation rate of 200 rpm, reaction time of 1.5 h, particle size of 500 μm, solid to liquid ratio of 1:2, additive amount of 40 wt% and oxygen pressure of 1.5 MPa. According to simulation results, the maximum conversion of released sulfide gases to H2SO4, recovery of KMnO4 and toxic heavy metals removal during designed process at optimized condition are 98%, 91% and 99%, respectively.