Insights into sulfur migration and transformation during the magnetization roasting of iron tailings and textile dyeing sludge

Magnetization roasting of iron tailings (IT) is an effective method to recovery fine iron concentrate (IC) from refractory IT. However, the migration and transformation of sulfur during the roasting process remain unclear, impacting iron quality if sulfur content exceeds the allowable limit value. This study investigates the sulfur release and fixation during magnetization roasting of textile dyeing sludge (TDS) and IT, elucidating the sulfur migration and transformation processes. Results indicate that 31.7 % of sulfur migrates to the gas phase due to the thermal decomposition of organic-S and the reduction of high-valent sulfur to SO₂ by H₂ and CO. The total sulfur (TS) content in tailing slag (TSL) (1.96 %) is significantly higher than that in the roasted product (RP) (0.84 %), suggesting a tendency for sulfur migration into TSL. This migration is attributed to reactions between H₂S/COS and Fe₂O₃/Fe₃O₄, resulting in the formation of non-magnetic byproduct FeS. Additionally, due to the symbiosis of hematite and sulfate, sulfur in the IC primarily exists as sulfate sulfur (76.98 %). This research is crucial for quality control in iron ore processing and provides theoretical guidance for sulfur regulation in practical production processes.