Thermodynamics and Kinetics on the Cementation Reaction of PbCl2 in the 50 mol%ZnCl2–50 mol%KCl Melt with Solid Zinc at 673 K

Abstract

Removal of PbCl2 from the 50 mol%ZnCl2–50 mol%KCl melt by the cementation reaction with solid zinc at 673 K was investigated in terms of thermodynamics and kinetics to develop a new recycling process of zinc from the electric arc furnace dust. A chloride sample (50 mol%ZnCl2–50 mol%KCl containing PbCl2 as an impurity) in a glass container was heated to 673 K, and zinc powder was added into the melt to remove PbCl2 by the reduction with zinc. In the equilibrium experiments by the addition of largely excess zinc, the limitation of PbCl2 removal by the cementation reaction at 673 K was measured. In the kinetic experiments by the addition of slightly excess zinc, the concentration of lead in the 50 mol%ZnCl2–50 mol%KCl melt at 673 K decreased rapidly from 2.91 to about 0.2 mass%Pb in 5 min, and finally reached about 0.04 mass%Pb after a 240-min reaction. The SEM/EDS analysis showed that the lead-rich phase was formed around the zinc phase. Finally, the reaction mechanism was discussed by applying the unreacted core model.