The removal of pyritic sulfur from Aşkale lignite in aqueous suspension by nitric acid

The removal of pyritic sulfur from a Turkish lignite in aqueous suspension by nitric acid was investigated. The effects of particle size (−60, −100 and −200 mesh), reaction time (0–10 800 s), nitric acid concentration (5–30 wt.%), temperature (25–103 °C) and speed of stirring (0.75–20 s−1) were studied. The pyritic sulfur was quantitatively removed at boiling temperature (≈103 °C in Erzurum) in 25% HNO3 solution.