Experimental Study of Leachability of Amorphous PbO-CuO-CaO-FeO-MgO-SiO₂ Slag: Methodology Development and Initial Results

There is a lot of potential in reusing metallurgical slag in geotechnical applications, with the primary concern for it is the susceptibility to natural leaching. A complex approach is essential to decrease the environmental impact of slag reuse and thus enhance the recycling of industrial slags. The current study is fundamental and focused on leaching behavior of amorphous slags in the CaO-“FeO”-MgO-SiO₂ system with heavy elements Pb and Cu. Compositions of synthetic slags are selected using the high-temperature equilibria studies and the predictions of internally developed thermodynamic models. The samples are prepared under laboratory controlled conditions and carefully characterized. Experimental technique for bulk leaching experiments is established to investigate pH-dependent elusion of elements into the leaching medium. Concentrations of the metals in the leachate is measured using ICP-MS. In addition, the micro-leaching tests devoted to investigation of slag surface structure before and after leaching are developed. Novel analytical techniques such as SEM/EPMA, TEM and XPS are implemented for analysis of slag-aqueous solution interface. Understanding of dissolution of amorphous glass phase that is present in all existing metallurgical slags is a critical step to provide a link between the chemical and phase composition of slags at high temperature, the cooling regime and leaching phenomena.