A highly selective and low-discharge method for vanadium extraction from vanadium slag: Low-calcification roasting-sodium bicarbonate leaching
Zibi Fu, Wenyi He, Yuzhong Rao, Guangchao Du, Ning Wang, Shiwei Wang
Abstract
• Low-calcification roasting-NaHCO 3 leaching for vanadium extraction was proposed. • A better separation of vanadium and impurities can be realized via NaHCO 3 leaching. • The vanadium precipitation wastewater can be directly recycled for clinker leaching. • The S content in residue and solid waste from wastewater are decreased significantly. • It realizes cleaner vanadium extraction and comprehensive utilization of resources. The current industrial processes for vanadium extraction from vanadium slag have common disadvantages, e.g., weak selectivity of vanadium and impurities (especially chromium), significant amounts of solid waste from wastewater treatment, and low utilization of the residue. This study proposes a new method featuring low-calcification roasting-sodium bicarbonate (NaHCO 3 ) leaching for vanadium extraction from vanadium slag. Theoretical analyses, process optimization, and characterizations were conducted for this method. Vanadium was selectively transformed into calcium pyrovanadate, manganese pyrovanadate and magnesium pyrovanadate by roasting the vanadium slag with added calcium oxide (3% by mass) at 900 °C for 100 min. Then, vanadium was leached into solution by NaHCO 3 at 95 °C for 120 min, resulting in vanadium and chromium leaching rates of 94.24% and 0.01%, respectively. The leaching residue exhibited sulfur and sodium contents of 0.005% and 0.57%, which has well potential for further utilization via recycling to blast furnaces. Subsequently, ammonium metavanadate (NH 4 VO 3 ) was obtained by vanadium precipitation from the leaching solution with ammonium carbonate as an additive. The wastewater generated after vanadium precipitation could be directly recycled to the next round of leaching. Finally, vanadium pentoxide with a purity of 99.61% was obtained by calcination of NH 4 VO 3 . This method has significant advantages of higher selectivity of vanadium extraction, minimization of solid waste, and higher potential for residue recycling. It provides a new insights for clean and efficient vanadium extraction as well as resources comprehensive utilization of vanadium slag.