Effect of Al 2 O 3 /SiO 2 mass ratio and CaO content on viscosity and structure of slag for pyrometallurgical processing of spent automotive catalysts

The effect of Al 2 O 3 /SiO 2 mass ratio and CaO content on the viscosity and structure of the CaO–Al 2 O 3 –SiO 2 –6MgO–1.5ZrO 2 –1.5CeO 2 slag was investigated. The results show that with the increase in Al 2 O 3 /SiO 2 mass ratio, the viscous flow units within the slag gradually change from Si–O–Si to Al–O–Al and Al–O–Si. Furthermore, the substitution of Al 2 O 3 for SiO 2 leads to the transformation of Si–O bonds towards weaker Al–O bonds, which weaken the bond strength of the aluminosilicate networks, thus leading to a decrease in the viscosity of slag. The increase in CaO content effectively promotes the depolymerization of the aluminosilicate networks, resulting in a significant decrease in the viscosity of the slag. The slag with Al 2 O 3 /SiO 2 of 0.7–1.5 and CaO of 30 wt.% shows promise as the reference slag system for the Fe-collection smelting of spent automotive catalysts due to its good comprehensive performance.