Co-roasting of tin tailings and waste cathode carbon for the recovery of Sn, Zn, Pb and F

Abstract

Tin tailings are a common type of solid waste containing Sn, Pb, Zn, Fe, Si, and Ca. Currently, most tin tailings are being stored in piles or landfills. This study proposes the co-roasting of tin tailings and waste cathode carbon(WCC) to allow for proper waste disposal. The result shows that ZnCO3 was transformed into ZnS-FeS eutectic, which restricted the formation Fe-Sn alloy. Simultaneous separations and recoveries of Sn, Pb, and Zn from tin tailings was realized under strong reducing atmosphere. Under optimal experimental conditions, the Sn, Pb and Zn recovery ratios were 95%, 98% and 95%, respectively. Additionally, NaF in the WCC was mainly transformed to CaF2, and 98% F can be solidified. The F, Pb, Zn, As, and Cu leached contents of the roasted residue in the toxicity characteristic leaching procedure(TCLP) met the national allowable emission standards. Iron phase could be reduced to high value metallic Fe, and its contents reached 88.75 wt% after magnetic separation. The tailings of magnetic separation can be reused as building materials, and CaF2 can enhance material properties, minimizing environmental risks. In industrial production, WCC can act as a fuel and reducant, which can significantly reduce tin tailings processing costs.

Keywords

• Tin tailings
• Waste cathode carbon
• Sn
• Pb and Zn recovery
• Harmlessness
• Co-roasting