Oxidation process of low-grade vanadium slag in presence of Na2CO3

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 degrees C. Olivine phases and spinel phases are completely decomposed at 500 and 600 degrees C, respectively. Most of water-soluble sodium vanadates are formed between 500 and 600 degrees C. When roasting temperature reaches above 700 degrees C, the vanadium-rich phases of sodium vanadates can be obviously observed. However, at temperature above 800 degrees 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.