A novel method for extracting vanadium by low temperature sodium roasting from converter vanadium slag

Abstract

Long-term high temperature in conventional vanadium extraction process would cause particles to be sintered and wrapped, thus reducing extraction efficiency of vanadium. Based on the purpose of directional conversion and process intensification, this work proposed a combination of low temperature sodium roasting and high efficiency selective oxidation leaching in vanadium extraction. The investigation of the reaction mechanism suggested that the structure of vanadium slag was changed by roasting, which also caused the fracture of spinel. The addition of MnO 2 promoted the directional oxidation of low-valent vanadium into high valence. It also found that Na 2 S 2 O 8 could oxidize low-valent vanadium effectively in leaching. The leaching efficiency of vanadium reached 87.74% under the optimum conditions, including a roasting temperature of 650 °C, a roasting time of 2.0 h, a molar ratio of sodium-to-vanadium of 0.6, a MnO 2 (roasting additive) dosage of 5 wt% and a Na 2 S 2 O 8 (leaching oxidant) dosage of 5 wt%. This percentage is 7.18% higher than that of direct roasting-and-leaching under the same conditions. • Low temperature roasting greatly reduced the energy consumption of vanadium extraction. • Sodium persulfate offered a significant selective oxidation for low-valent vanadium. • No other cationic ions were introduced with the addition of sodium persulfate in sodium-modification system, while the sulfate radical formed by sodium persulfate could also be used as reactant in the subsequent precipitating vanadium. • The leaching efficiency of low temperature roasting-oxidative leaching method achieved 87.74%, which was 7.18 % higher than that of direct roasting-and-leaching under the same conditions.