Characterization of blast furnace sludge and removal of zinc by microwave assisted extraction

Significant quantities of sludge and slag are generated as waste materials or byproducts every day from steel industries. The blast furnace sludge (BFS) is considered to be highly problematic, due to zinc content. Therefore, new technological processes for recycling the sludge and dusts from metallurgical processes are still searched to find the most suitable method. One direction toward a cleaner environment is to use microwaves as energy source to enhance leaching processes of BFS. The presented work is focussed on the removal of zinc from BFS in an attempt to allow the reuse of the sludge with relatively high iron content in the subsequent production steps. Fine fractions of BFS are characterized and treated by the microwave assisted leaching for selective removal of zinc. The effects of extraction conditions such as microwave power, leaching agent, acid concentration, L/S ratio and extraction time for the zinc removal efficiency are evaluated. To completely describe the leaching kinetics, the shrinking core models are used to determine the apparent activation energy and the rate-limiting step of the reaction.