Magnesiation roasting-acid leaching: A zero-discharge method for vanadium extraction from vanadium slag

Present methods of vanadium extraction from vanadium slag suffer from serious environmental pollution due to the large production of solid waste and wastewater. This study proposes a cleaner method of magnesiation roasting-acid leaching, where magnesium oxide is considered to be a recyclable roasting additive. The maximum extraction efficiency achieved in case of vanadium is 95.56%, and the obtained vanadium pentoxide has a high purity of 99.07%. The magnesium in the leaching liquor is recovered as MgO with purity of 99.21%, and recovery rate of 90.13%, which is recycled as the roasting additive. Furthermore, manganese, ammonium sulfate, and water are recovered and recycled from the wastewater, while the ammonia produced during vanadate calcination is recycled. The resulted leaching residues are recyclable by burning in a blast furnace to recover their iron content for reuse. Herein, the recycling and reuse of all the wastewater and leaching residues result in zero discharge, significant cleanliness, and high resource utilization. This work has opened a new pathway of establishing significantly cleaner production process for environmental sustainability via design and incorporation of inner recycling of wastes into the process in which these wastes are produced. (C) 2020 Elsevier Ltd. All rights reserved.