The critical applications of vanadium in metallurgical field and the growth in commercialization of vanadium redox flow batteries (VRFB) have led to the increased demand of vanadium. It is thus important to ensure the sustainability of vanadium production. Vanadium bearing slags, the solid byproducts in iron- and steel-making plants, are the principal source of vanadium production, accounting for more than 69% of total vanadium in terms ofthe raw material types. Academic researches and engineering investigations have been addressed to develop such metallurgical processes for treating the vanadium bearing slags. This article presents a comprehensive review on the metallurgical treatments of vanadium bearing slags. The composition and phase/mineralogical characterization of vanadium bearing slags from various sources are given. Literature review shows that the vanadium bearing slags have been traditionally treated through the roasting-assisted leaching with the recent efforts of integrating the state-of-the arts technologies in extractive metallurgy and developing direct leaching methodologies. Some promising methods are worth discussing and quite encouraging, and expected to be the future focuses of this area. Discussion also highlights the separation of vanadium from silica, phosphorus and chromium as the major interfering elements/metal in the leach solutions of vanadium slags. Recommendation is made for taking up future works in order to develop a sustainable metallurgical process for vanadium bearing slag.

A review on the metallurgical recycling of vanadium from slags: towards a sustainable vanadium production

Efficient extraction and separation of vanadium and chromium in high chromium vanadium slag by sodium salt roasting-(NH4)2SO4 leaching

Calcification roasting–acid leaching of high-chromium vanadium slag (HCVS) was conducted to elucidate the roasting and leaching behaviors of vanadium and chromium. The effects of the purity of CaO, molar ratio between CaO and V2O5 (n(CaO)/n(V2O5)), roasting temperature, holding time, and the heating rate used in the oxidation–calcification processes were investigated. The roasting process and mechanism were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetry–differential scanning calorimetry (TG–DSC). The results show that most of vanadium reacted with CaO to generate calcium vanadates and transferred into the leaching liquid, whereas almost all of the chromium remained in the leaching residue in the form of (Fe0.6Cr0.4)2O3. Variation trends of the vanadium and chromium leaching ratios were always opposite because of the competitive reactions of oxidation and calcification between vanadium and chromium with CaO. Moreover, CaO was more likely to combine with vanadium, as further confirmed by thermodynamic analysis. When the HCVS with CaO added in an n(CaO)/n(V2O5) ratio of 0.5 was roasted in an air atmosphere at a heating rate of 10°C/min from room temperature to 950°C and maintained at this temperature for 60 min, the leaching ratios of vanadium and chromium reached 91.14% and 0.49%, respectively; thus, efficient extraction of vanadium from HCVS was achieved and the leaching residue could be used as a new raw material for the extraction of chromium. Furthermore, the oxidation and calcification reactions of the spinel phases occurred at 592 and 630°C for n(CaO)/n(V2O5) ratios of 0.5 and 5, respectively.

Roasting and leaching behaviors of vanadium and chromium in calcification roasting–acid leaching of high-chromium vanadium slag

A cleaner and efficient process for extraction of vanadium from high chromium vanadium slag: Leaching in (NH4)2SO4-H2SO4 synergistic system and NH4+ recycle

Efficient separation of chromium and vanadium by calcification roasting–sodium carbonate leaching from high chromium vanadium slag and V2O5 preparation

The extraction of vanadium and chromium from high chromium content vanadium slag by salt roasting and water leaching process has been investigated, which uses mixed sodium salts (Na2CO3 and NaOH) as additive agent in roasting process. The mineralogical morphology was prospected by TG-DSC, XRD, SEM and EDS. The oxidation of slag and transversion of V/Cr-containing phase and sodium salts have been discussed. It has been demonstrated that the presence of NaOH contributes to decompose spinel and olivine phases, which is beneficial to reduce the roasting temperature and elevate V, Cr leaching ratio. The roasting parameters have been studied as a function of roasting temperature, roasting time and ratio of alkali, in which the roasting temperature is the most effective factor on the leaching rate of vanadium and chromium. Under the optimum condition, the leaching rates of V and Cr reached 95.8% and 97.6%, respectively.

Yi Peng

Papers

Effective Extraction of Vanadium and Chromium from High Chromium Content Vanadium Slag by Sodium Roasting and Water Leaching