Recovery of valuable metals from EAF steel making dust by hydrometallurgy

Purpose and goal

Detailed characterization was done before hydrometallurgical treatment and also the solid rest after the leaching were characterized to find out how much of the Zn stayed in the solid sample and in which phase. In the second part, the hydrometallurgical study determined the effects of studied parameters on zinc leaching as well as on the impurities leaching. Based on the results the optimal conditions were selected to leach out the zinc obtaining quite high efficiencies (80%) in a single step. Zinc was recovered selectively from iron and other impurities.

Results and expected effects

The characterization has shown the presence of the phase franklinite, in which Zn is entrapped. It was found out that three samples are suitable source for zinc recovery. The hydrometallurgical study has provided information for a selection of the optimal leaching conditions. It was determined that higher temperature is needed to reach high efficiency. 8M NaOH solution is sufficient for a Zn recovery at given conditions. Solid to liquid ration can be lowered to 1/30 sustaining the effectivity of the process. Zinc can be recovered from such a material in less than two hours.

Approach and implementation

The characterization has shown that 3 samples are suitable for Zn recovery. The Zn content more than 30% gives the opportunity to develop a process for a Zn recovery from such a waste. Additional characterization provided detailed information about such a material, which can be very useful for considering the recycling technology design. Alkaline leaching was proven to be an efficient way how to recover Zn selectively from the Fe and the other present impurities. The optimal conditions for such a process were determined in this project and can be used for a recycling process development.