The Thermodynamic Behavior of Copper in the CaO-B₂O₃ and BaO-B₂O₃ Slag System

Abstract

The Cu solubility was measured in the CaO-B₂O₃ and BaO-B₂O₃ slag systems to understand the dissolution mechanism of Cu in the slags. The Cu solubility had a linear relationship with oxygen partial pressure in the CaO-B₂O₃ slag system, which corresponds with previous studies. Also, the Cu solubilities in slag decreased with increasing the slag basicity, which value of slope was close to –0.5 in logarithmic form. From the results of experiment, the Cu dissolution mechanism established as follows:

$$ {\text{Cu}} + \frac{1}{4}{\text{O}}_{2} = {\text{Cu}}^{ + } + \frac{1}{2}{\text{O}}^{2 - } $$

To compensate the effects of oxygen partial pressure and chemical potential of Cu in alloy on the Cu solubility of slag, the concept of cuprous capacity was suggested as follows:

$$ C_{{\rm Cu^{ + } }} = \frac{K}{{f_{{\rm Cu^{ + } }} \cdot a_{{\rm O^{2 - } }}^{\frac{1}{2}} }} = \frac{{({\text{mass pct Cu}})}}{{a{}_{\rm Cu} \cdot p_{{\rm O_{2} }}^{\frac{1}{4}} }} $$

The cuprous capacity showed decreasing tendency as the slag basicity increased in the B₂O₃ bearing slags as well as in CaO-SiO₂-Al₂O_3(Satd.) and FeO-Fe₂O₃-SiO_2(Satd.) slag systems. It is suggested that the proposed dissolution mechanism could be available in various slag systems.