Recovery of useful metals from metal dust from steel production with hydrochemical methods

Purpose and goal
Detailed characterisation was done before hydrometallurgical treatment and also the solid rest after the leaching were characterised to find out how much of the zinc 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.

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

Expected results
The characterisation has shown the presence of the phase franklinite, in which zinc is entrapped. It was found 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 zinc recovery at given conditions. The solid to liquid ratio 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.