Thermodynamic model of lead oxide activity in PbO–CaO–SiO2–FeO–Fe2O3 slag system

According to the ion and molecule coexistence theory, a thermodynamic model of lead oxide activity in PbO–CaO–SiO2–FeO–Fe2O3 slag system was established at the temperature of 1273–1733 K. The activities of PbO in slag were calculated, and their equal activity curves were plotted. The influences of slag basicity Q, iron oxide rate R and temperature T on activity NPbO and activity coefficient γPbO were also investigated. Results show that the calculated values of γPbO are in good agreement with the reported experimental data, showing that the model can wholly embody the slag structural characteristics. NPbO departures positively from Raoult values, and increases with increasing PbO content in slag but changes little with T. γPbO increases with increasing Q, and goes through the maximum with increasing R for basic slag (Q<0.3). Results can be applied to the thermodynamic research and operational optimization of modern lead smelting technologies.