Factors influencing the Zn and Mn extraction from pyrometallurgical sludge in the steel manufacturing industry

• Removal of Zn, Mn and Pb from dust from steel manufacturing industry was studied.
• The parameters influencing the leaching of Zn and Mn were investigated.
• The Box–Behnken methodology was used to determine the optimal leaching conditions.
• Optimal leaching conditions removed 100% of the Mn and 75% of the Zn.

In this laboratory study, a process has been developed for selectively leaching zinc and manganese from pyrometallurgical sludge produced in the steel manufacturing industry. In the first part, the yield of Zn extraction was studied using four factors and four levels of the Box–Behnken response surface design. The optimum conditions for the step of Zn leaching were determined to be a sulfuric acid concentration of 0.25 mol/L, a pulp density of 10%, an extraction temperature of 20 °C, and three stages of leaching. Under such conditions, 75% of the Zn should be leached. For Mn leaching, the optimum conditions were determined to be a sulfuric acid concentration of 0.25 mol/L, a Na2S2O5/Mn stoichiometry of 1, a leaching time of 120 min and two leaching steps. In this case, 100% of the Mn should be leached.