Abstract:The oxidation process of low-grade vanadium slag in the presence of Na₂CO₃ was investigated by XRD, SEM/EDS and TG-DSC techniques. The results show that the vanadium slag is oxidized in a temperature range from 273 to 700 °C. Olivine phases and spinel phases are completely decomposed at 500 and 600 °C, respectively. Most of water-soluble sodium vanadates are formed between 500 and 600 °C. When roasting temperature reaches above 700 °C, the vanadium-rich phases of sodium vanadates can be obviously observed. However, at temperature above 800 °C, the samples are sintered. Most of the vanadium is enwrapped by glassy phase compounds which lead to the decrease of the leaching rate of vanadium. At the same time, the effect of roasting temperature on extraction of vanadium and characterization of leach residues were discussed.

Key words: low-grade vanadium slag; Na₂CO₃; roasting; vanadium-rich phases; leaching