Microstructure and Mineral Phase Evolution of Vanadium Slag by Modulating the CaO/V2O5 Ratio

The slag mineral phase is reconstructed by adding CaO to the molten vanadium slag to obtain a slag with high metallurgical characteristics. In this paper, the effects of the CaO/V2O5 ratio on the microstructure of molten vanadium slag, the phase composition of vanadium slag, and the non-salt roasting-(NH4)(2)CO3 leaching performance of modified vanadium slag were comprehensively investigated. Molecular dynamics simulation was used to examine the microstructure of the simplified vanadium slag system (FeO-V2Ox-SiO2-CaO) at varied CaO/V2O5 ratios. The results show that V (3+, 4+, and 5+) in the molten vanadium slag is similar to the network former. The V-O structure is dominated by four-fold coordination, and V3+ and V5+ show rich coordination configurations. With the increased CaO content, the overall diffusivity of the system increases, and the network structure is destroyed by CaO. The addition of CaO realizes the mineral phase reconstruction of vanadium slag, and vanadium slag with a more concentrated vanadium distribution and a wider Ca distribution is obtained. The concentration of vanadium in vanadium spinel increases from 17% to 29.4%. A suitable CaO/V2O5 ratio reduces the dependence of the vanadium leaching recovery on the vanadium slag's roasting temperature and duration.