Study on the Activity Model of PbO-ZnO-FeO-Fe₂O₃-SiO₂-CaO Six-Component High-Lead Slag System

Abstract

In this paper, the thermodynamic properties of the PbO-ZnO-FeO-Fe2O3-SiO2-CaO six-component slag system were studied by using the molecular-ion coexistence theory, and the influence of slag composition changes on the activity of each structural unit was analyzed. The results show that the calculated value of the activity model is in good agreement with the measured value of the experiment, and the activity of each structural unit is greatly affected by the composition of the slag, but less affected by the temperature. High temperature is conducive to the decomposition of lead silicate and the formation of calcium-containing compounds, but the activity of ZnO will decrease. When the mass fraction of PbO increases, the main reaction is to combine with PbO·SiO2 to form 2PbO·SiO2. Increasing the mass fraction of ZnO and CaO is beneficial to the decomposition of lead silicate and an increase in PbO activity. When the iron-silicon ratio increases, it will promote the decomposition of lead silicate and the formation of ZnO·Fe2O3, so the activity of PbO will increase and the activity of ZnO will decrease. When the calcium-silicon ratio is low, the binary combination product of CaO and SiO2 is mainly CaO·SiO2, and when the calcium-silicon ratio rises above 0.5, the activities of 2CaO·SiO2 and 3CaO·2SiO2 will increase rapidly.

Keywords

• high-lead slag
• molecular-ion coexistence theory
• activity
• thermodynamic model