Influence of manganese component on vanadium precipi-tation process and V2O5 purity based on different roasting methods of vanadium slag

Manganese was the main impurity in acidic vanadium-bearing leaching solution, and its effects on vanadium precipitation by hydrolysis and acidic ammonium salt were currently unclear. In this work, vanadium-bearing leachates with different manganese contents (VL-cMn) prepared on the basis of calcium, calcium-manganese composite and manganese roasting of vanadium slag (VS) were con-ducted to study the influence of manganese on precipitation characteristics of vanadium during hy-drolysis precipitation (HP) and ammonium-salt precipitation (AP), as well as microscopic character-istics and purity of V2O5 products. Results shown that increased pH value would weaken the adverse effect of manganese on V precipitation rate for HP. However, with increasing manganese from 5.69g/L to 15.38g/L, V precipitation rate decreased gradually at higher temperature and longer reaction time. Density of the microstructure of precipitates increased, which may contribute to the formation of Mn-bearing phases. Further, the average grains size of V2O5 was reduced and agglomerated gradually, and the purity of V2O5 products was decreased by 2.55%. For precipitation by acidic ammonium salt, with increasing manganese content, improving pH value could eliminate the negative effect on V pre-cipitation rate and lower the amount of ammonium sulfate. Additionally, manganese was unevenly adsorbed on the surface of precipitates. The grains of V2O5 gradually shrank and became dense, but it had no significant impact on purity of V2O5 products, which was higher than 99.3%. Finally, it was concluded that roasting of adding manganese salts affected hydrolysis of vanadium, but essentially did not affect acidic ammonium salt precipitation.