Fayalite Based Slags: Metal Recovery And Utilization

Fayalite based slag has already been used for a long time in copper metallurgy. The production of copper from both ores and secondary resources results in major amounts of fayalite slag at a rate of 2.2 ton slag per ton of produced copper. Fayalite slag still contains valuable metals in concentrations sometimes exceeding the content of current natural ores. Rather than being a waste, the slag residue itself can be used in different applications. In order to utilize fayalite based slag and improve the sustainability of the copper metallurgical process, new extraction techniques and slag applications need to be implemented or developed. Although fayalite is the main phase, the resulting microstructure and metals content of the slag slightly differs depending on the metallurgical process and the cooling practise. Applicable techniques for metal recovery and slag utilization depend on the final microstructure of the slag. This paper reviews existing and novel routes for metal recovery and fayalite slag utilization. Firstly, an estimate of the amounts of old and currently produced fayalite slags together with differences in microstructure is given. Secondly, existing and novel techniques to recover metals from fayalite slag are discussed. Thirdly, the utilization of fayalite slag in for example construction applications is described in relation to leaching of metals. Future prospects for fayalite slag research will be indicated for recovery of the remaining metals and utilization of the slag or residues subsequent to metal recovery.