Extraction of vanadium from vanadium slag by sodium roasting-ammonium sulfate leaching and removal of impurities from weakly alkaline leach solution

Abstract

In the present work, a sustainable process for extraction of vanadium (V) from vanadium slag was proposed. The vanadium slag was first roasted by Na2CO3, then leached by (NH4)2SO4. The effect of roasting and leaching conditions on V and major impurities (P, Si) leaching have been systematically investigated. The results indicated that under the optimal conditions (roasting conditions: 18% Na2CO3, 800 °C, 2.5 h; leaching conditions: 30 g/L (NH4)2SO4, 60 °C, 3 mL/g, 0.5 h), the leaching rates of V, P and Si were 91.2%, 35.3% and 2.5%, respectively. Subsequently, Al2(SO4)3·18 H2O was used to simultaneously remove P and Si from the leach solution without pH adjustment, 92.3% and 86.6% of P and Si were removed with n(Al)/n(P + Si) of 2, temperature of 70 °C and 20 min. Ammonium metavanadate in the impurity removal solution can be directly separated by cooling crystallization without adjusting pH or adding ammonium salt. Meanwhile, the wastewater can be reused for leaching, which can effectively solve the difficult treatment of wastewater containing ammonia nitrogen. Leaching residue with Fe content of 45%, which can be applied to extract iron.