Mineral evolution mechanism of Zinc-slag during high-temperature reactive process

Abstract

The mineral transformation mechanism, microstructure evolution and chemical reactivity of Zinc-slag sintered at 1350–1550 °C for 10–60 min were systematically studied using Fe2O3, Al2O3, SiO2, CaO, MgO and ZnO as raw simulation materials. The molar ratio, sintering temperature and duration could affect the ions diffusion and migration in molten state attributing to the acid-base equilibrium and the energy of atomic thermal motion, and then influence the phase formation and transition process. Meanwhile, the FactSage software was used to calculate the equilibrium polyphase diagram for predicting the phase transformation mechanism of non-equilibrium system, while the Si4+ and Al3+ react with Ca2+ easily due to the tetrahedral structure. The phase composition of Zinc-slag contains Ca2Al2SiO7, Ca3(Si3O9), ZnFe2O4, Fe2O3, SiO2 and Fe when sintered at 1500 °C for 60 min, and it also has the optimal Zinc recovery efficiency of 91% with 1.2 mol/L H2SO4 and 0.04 mol/L H2S2O8 attributing to the large layer spacing and uniform distribution of ZnFe2O4. The lime sinter process with acid-leaching technology is beneficial to effectively improve the utilization rate of Zinc-slag, and it also could provide a strategy to solve the environmental pollution problem caused by industrial waste slag.