Elucidation of precious metal-slag-refractory reaction and dissolution mechanism of palladium in slag for recovery of precious metals from industrial waste

Abstract

To establish the dissolution mechanism of palladium (Pd) in the FetO-SiO2-CaO- Al2O3- MgOsat slag system, the Pd solubility was measured at a temperature of 1873 K and partial oxygen pressure ranging from  = 1.0 × 10 to  = 1.0 × 10 atm. In the current slag system, the Pd solubility increases with increasing CaO and FeO content, while it decreases with increasing SiO2 and Al2O3 content. This solubility behavior is quantified by the modified Vee ratio, defined as ((CaO + FeO) / (SiO2 + Al2O3)), which increases as the theoretical optical basicity and the activity of CaO increase. Thermodynamic analysis reveals that Pd stabilizes in the form of   complex ion. Based on this, the mechanism of Pd dissolution in the current slag system is proposed as follows :

() + 1 4  () + 3 2 ( ) = ( ) Combining the results from this experiment and previous findings suggests that a welldesigned slag system can effectively minimize Pd loss during the pyrometallurgical processing of industrial wastes containing Pd. By adjusting the ratio of basic oxides, such as CaO and FeO, which promote Pd solubility in the slag, along with SiO2, which increases viscosity, it is possible to achieve optimal conditions. Therefore, we recommend implementing such an optimized slag system for the pyrometallurgical treatment of Pdcontaining industrial wastes, ensuring minimal Pd loss and maximizing resource recovery.