Recovery of vanadium from vanadium slag by composite additive roasting-acid leaching process

To minimize the vanadium content in the vanadium extraction tailings, composite additive roasting with (CaO + MgO) and subsequent acid leaching process was carried out dealing with vanadium-bearing converter slag. The effect of additive with different MgO/(CaO + MgO) molar ratios on the roasting and leaching behaviours of vanadium slag was investigated, and the optimum process conditions were obtained. The results show that in the roasting experiment, under the conditions of roasting temperature of 850 degrees C and roasting time of 2 h, the main kinds of vanadate transformed from Ca2V2O7 to Ca5Mg4V6O24 and then to Mg2V2O7 with the increase in the MgO/(CaO + MgO) molar ratio. In the leaching experiment, under the conditions of particle size less than 75 mu m, leaching temperature of 50 degrees C, pH of 2.5, liquid-solid ratio of 20:1, and MgO/(CaO + MgO) molar ratio of 1:3, the leaching efficiency of vanadium is increased by about 5%, but the substitution of MgO for most or all of CaO will significantly reduce the leaching efficiency of vanadium. Furthermore, the leaching efficiency of impurities (P and Cr) can also be decreased by a composite addictive (CaO + MgO) roasting process. The X-ray diffraction, scanning electron microscopy, energy dispersive spectrometry, and X-ray photoelectron spectroscopy of the original vanadium slag and solid products of both roasting and leaching processes were also evaluated.

Automated summary

A composite additive roasting and acid leaching process was applied to reduce the vanadium content in vanadium extraction tailings from vanadium-bearing converter slag. The effect of additive with different MgO/(CaO + MgO) ratios on the roasting and leaching behaviors of vanadium slag was investigated, and the optimal process conditions were determined. The results showed that the addition of MgO could transform the vanadate species in the slag, but excessive MgO substitution for CaO reduced the leaching efficiency of vanadium.