Effect of Al2O3 on Viscosity and Structure of SiO2-FeO-Al2O3-Fe2O3-CaO-MgO Slag System

In this study, the effect of Al2O3 content on viscous behaviors of the secondary copper smelting slags was investigated in depth. It was determined that in the slag system of SiO2-FeO-Al2O3-12 wt.%Fe2O3-8 wt.%CaO-3 wt.%MgO, the addition of Al2O3 (0–12 wt.%) increased the slag viscosity and activation energy for viscous flow (Eη). The breaking temperature of the slag (TBr) exhibited a minimum value at the Al2O3 addition of 6 wt.%. X-ray diffraction (XRD) tests and thermodynamic calculations indicated the increase of Al2O3 content can promote the precipitation of fayalite and anorthite phases and simultaneously suppress the precipitation of clinopyroxene phase. Moreover, Fourier transform infrared (FTIR) and Raman spectroscopy suggested that Al2O3 presented acidic oxide properties and acted as a network former to increase the polymerization of the melt. As the Al2O3 increased, the aluminium–oxygen tetrahedra copolymerized with silicon–oxygen tetrahedra, forming a more complex aluminosilicate composite network structure.