Separation of iron and calcium from a BSSF steelmaking slag through acid leaching

Abstract

Considering the BSSF steelmaking slag generated in a Brazilian steelwork, it would be worth to separate iron and calcium from it, with the objective of increasing its iron content, or producing Fe2O3 and CaO by selective precipitation from cations in aqueous solution. In this way, materials could be produced and used in-house, e.g., sintering plant. This possibility was explored through acid leaching for an industrial sample. A possibility to increase concentration of iron of the slag is to leach it with a 2 mol.L-1 HCl solution; in this condition, 63.6% of the CaO is extracted from the slag to the aqueous solution, and Fe content of the slag increases from 27.4 to 37.1 wt%. Another possibility is to use HCl 5 mol.L-1; in this condition, 86.8% of the Fe and 90.7% of the CaO are transferred to the liquid solution. Then separation of iron and calcium can be achieved by selective precipitation: firstly, adding ammonia to precipitate Fe(OH)3, and then calcinating it to produce Fe2O3 (~ 200 °C); in the following, adding sodium carbonate to precipitate CaCO3, which in turn can be calcinated to produce CaO (~ 900 °C). In this way, Fe2O3 and CaO could be produced.