Evaluation of the process parameters for the zinc extraction from blast furnace sludge using chemical, physical and mechanico-chemical methods

The blast furnace sludge of Esfahan steel company contains heavy metals therefore its improper disposal is harmful to the environment. However, due to its high iron content, the recovery of iron is valuable, while the presence of about 4% zinc in the sludge has limited the direct recycling of the sludge. The aim of this research was to develop a method for selective dissolution of zinc. The efficiency of different hydrometallurgical methods (including: atmospheric leaching, microwave leaching, magnetic separation, ultrasonic, thermal preparation, autoclave leaching, mechano-chemical and thermal leaching) were used and the influence of temperature, solvent concentration, liquid to solid ratio and operation time on zinc and iron dissolution was determined. Results showed that thermal preparation methods followed by basic leaching leads to 85% increase in dissolution of zinc and the minimum dissolution of iron (1.2%). Also, the most important parameters in dissolution of zinc are temperature (90 °C) and leaching agent concentration (6 molar) and the most effective factor in iron dissolution is temperature.