Characterization of cast iron and slag produced by red muds reduction via Arc Transferred Plasma (ATP) reactor under different smelting conditions

Plasma treatment is a process have demonstrated its feasibility in industrial waste remediation, both for vitrification of toxic wastes into stable slag and recovery of valuable metals from such wastes. In this paper, arc transferred plasma technology was employed for the treatment of red muds, the most concerning waste of Bayer process. Red muds were mixed with different proportion of metallurgical coke (6 and 12 %wt.) and slag conditioners (CaO and SiO2) and thermally reduced to obtain valuable metals recovery and safe manageably slag. As a function of the mix proportion, reduction of red mud leads to the production of cast iron, accompanied by the formation of a crystalline or glassy slag. Cast iron quality was evaluated trough chemical and microstructural characterization, to identify possible markets where it can be valorised. As well, the different obtained slag where characterized from a chemical, crystallographic, and environmental point of view to identify possible management and valorisation. By an excess of coke, strong iron oxide reduction can be achieved (95 %), with negligible iron loss in the slag (< 2 %wt.). By controlling the basicity (CaO/SIO2) of the mix, a full developed amorphous slag can be obtained, with a reduced environmental impact and strong inertness against leaching.