Microwave caustic leaching of electric arc furnace dust

Electric arc furnace (EAF) dust is a waste product which is generated when steel scrap is melted in an electric arc furnace. It contains high concentrations of iron, zinc and lead. Numerous pyrometallurgical and hydrometallurgical processes have been developed to treat this material. Only a limited number of these have reached commercialization and the majority have been pyrometallurgical. However, the hydrometallurgical processes, such as caustic leaching, offer some potential advantages.In the present research, the application of microwave radiation at 2.45 GHz was employed, as the energy source, in the hydrometallurgical caustic leaching process for EAF dust treatment. The variables which were investigated were: leaching time, microwave power, caustic concentration and the solid to liquid ratio. The experimental results showed that the zinc recovery from the dust increased with a decrease in the solid to liquid ratio and an increase in the microwave power. The optimum caustic concentration for the maximum zinc recovery was 8M. The rates of zinc recovery were significantly higher under microwave conditions as compared to those observed with conventional leaching. Some possible mechanisms to explain this behaviour are discussed.