Efficient Zinc Removal from Blast Furnace Sludge Using Choline Chloride-Malonic Acid: Towards Sustainable Recycling of Iron Extraction Waste

Chemical components of blast furnace sludge (BFS) of iron blast furnaces become a recyclable raw material in the furnace when a few contents including zinc (Zn) are selectively removed. Out of four deep eutectic solvents (DES) preselected from the literature for their potential selective Zn leaching performances, choline chloride-malonic acid was determined to be the most efficient DES for its efficiency in removing Zn from BFS in the presence of iron (Fe). Further preliminary tests were conducted via iterations of leaching parameters to determine their individual effects on the leaching efficiencies for Zn, Ca, and Fe. Parameters like DES concentration, leaching period, and solid/liquid ratio were found to be the most accountable, as agitation speed and temperature showed only a slight influence on the efficiencies. For a maximum Zn removal of about 85% with the least amount of Fe of around 15%, the empirical parameters without any extra optimization were estimated to be 30 vol.% malonic acid concentration, 1/4 (g/mL) solid/liquid ratio, 100 rpm agitation speed, 60 & DEG;C leaching temperature, and 3.0 h leaching period.