Solidification mechanism and harmful elements removal behavior in preparation of sulfuric acid slag pellets

Sulfuric acid slag, a common byproduct with high iron content, poses challenges due to its high levels of harmful impurities and is often discarded as solid waste, leading to significant environmental and water pollution. To address this issue and improve resource utilization, the preparation process of oxidized pellets from sulfuric acid slag was studied, exploring suitable pelletizing systems and thermal parameters. Additionally, the removal of harmful elements and the consolidation mechanism were established during the oxidation roasting process. The findings revealed that sulfuric acid slag along with specific processing conditions, such as using two high-pressure grinding rolls and adding 1.25 wt.% bentonite, resulted in the production of qualified green pellets with desirable physical properties. Through a thermal treatment process involving preheating and roasting, the desulfurization rate of the pellets reached 95.55% and the removal efficiency of arsenic achieved 27.11%. Hematite recrystallizes, shrinks, and forms a reticulated structure with Fe₂O₃ recrystallization as the backbone, resulting in higher consolidation strength.