Effect of chemical composition on the element distribution, phase composition and calcification roasting process of vanadium slag

The chemical composition of vanadium slag significantly affects its element distribution and phase composition, which affect the subsequent calcification roasting process and vanadium recovery. In this work, seven kinds of vanadium slags derived from different regions in China were used as the raw materials to study the effects of different components on the vanadium slag’s elements distribution, phase composition, calcification roasting, and leaching rate of major elements using scanning electron microscope, X-ray diffraction analysis, and inductively coupled plasma-optical emission spectroscopy. The results show that the spinel phase is wrapped with silicate phase in all vanadium slag samples. The main elements in the spinel phase are Cr, V, and Ti from the interior to the exterior. The size of spinel phase in low chromium vanadium slag is larger than the other vanadium slags with higher chromium contents. The spinel phase of high-calcium and high-phosphorus vanadium slag is more dispersed. The strongest diffraction peak of vanadium spinel phase in the vanadium slag migrates to a higher diffraction angle, and(Fe0.6Cr0.4)2O3is formed after calcification roasting as the chromium content increased. A large amount of Ca2SiO4is produced because excess Ca reacts with Si in high-calcium and high-phosphorus vanadium slag. The vanadium leaching rate reaches 88% in some vanadium slags. The chromium leaching rate is less than 5% in all vanadium slags. The silicon leaching rate of high-calcium and high-phosphorus vanadium slag is much higher than that of the other slags. The leaching rate of manganese is higher than 10%, and the leaching rates of iron and titanium are negligible.