Cleaner Recycling of Jarosite Residue by Ca(OH)2 Leaching-Biomass Magnetization Roasting

A combined hydrometallurgical and pyrometallurgical process is proposed for the treatment of jarosite residue from zinc hydrometallurgy. The main steps of the proposed process include Ca(OH)₂ leaching for the ammonium component, biomass magnetization roasting, and magnetic separation. The optimal conditions for Ca(OH)₂ leaching were determined as follows: Ca(OH)₂ dosage of 25%, L/S ratio of 15, leaching temperature of 70°C, and leaching time of 60 min, resulting in a 96.27% ammonia jarosite decomposition rate. During the biomass roasting process, with corn cob as the reductant, the biomass at a ratio of 0.75, and roasting at 800°C for 90 min, a reduction rate of 43.61% was achieved. Magnetic separation was then performed, resulting in a magnetic concentrate with an iron grade of 67.56% and iron recovery of 83.20%. SEM-EDS analysis showed reduction products with abundant microcracks and a loose structure. Research on the use of biomass as an alternative reductant for magnetization roasting is of great significance for emission reduction and green production.