Thermodynamics of Indium Dissolution Behavior in FeO-Bearing Metallurgical Slags

Indium solubility in the FeO-SiO₂-Al₂O₃-5CaO-MgO_sat slag system was measured at 1573 K (1300 °C) to confirm the thermodynamic dissolution behavior of indium at \( {\text{p}}_{{\text{O}_{2} }} = 10^{ - 11} \) atm. The indium solubility in FeO-bearing slags increased with increasing oxygen partial pressure and decreased with increasing basicity which is in proportion to the activity of FeO. The dissolution of indium in FeO-bearing slags was confirmed to progress according to the following reaction: The enthalpy change for the dissolution of indium in FeO-bearing slag was about −181 kJ/mol, indicating that indium dissolution is exothermic. The indium solubility in the FeO-SiO₂-Al₂O₃-5CaO-MgO_sat slag system was minimized as a function of alumina content at a given FeO/SiO₂ ratio, which can be explained by the amphoteric behavior of Al₂O₃ in the slag system. To improve indium recovery by lowering indium loss to the slag phase during the pyro-recycling of In-containing materials using FeO-bearing metallurgical slags, a lower oxygen potential and lower silica content are highly favorable.