Leaching Kinetics of Vanadium from Calcium-Roasting High-Chromium Vanadium Slag Enhanced by Electric Field

Abstract

Vanadium exists as multivalent valences in high-chromium vanadium slag, and it is hard to leach out in low valence. Electro-oxidation technology has been applied to enhance the leaching process of calcium-roasting high-chromium vanadium slag. The effect of parameters that affect the leaching efficiency of vanadium including concentration of sulfur acid, current density, reaction temperature, and liquid-to-solid ratio was investigated. The results showed that vanadium in low valence could be oxidized and efficiently leached out enhanced with electricity. The leaching kinetics was analyzed, which indicates that the leaching rate was controlled by the surface chemical reaction with an apparent activation energy of 40.11 kJ/mol. On the basis of this process, vanadium could be efficiently leached out with a leaching efficiency of 92.14% under optimal conditions: concentration of sulfur acid of 40 vol %, current density of 750 A/m 2 , reaction temperature of 90 °C, reaction time of 180 min, particle size under 75 μm, liquid-to-solid ratio of 4:1 mL/g, and stirring rate of 500 rpm. The relationship between the leaching efficiency and the parameters affecting the leaching process could be described as 1 – (1 – x ) 1/3 = K 0 × [H 2 SO 4 ] 0.1390 × [ J ] 0.03354 × [ T ] 2.8247 × [ L / S ] −0.2598 × exp 40.11/ T × t .

Efficient Recovery of Vanadium from High-Chromium Vanadium Slag with Calcium-Roasting Acidic Leaching

“…The XPS results showed that most vanadium existed as V(III) and V(IV) (515.7 eV and 516.4 eV), and the Cr (III) accounted for about 82.84% of the HCVS (576.1 eV, 577.3 eV and 586.3 eV), while there were no V (III) and V (V) phases in the XRD pattern. According to our previous study, V(III), V(IV), and V(V) co-exist in HCVS, which means that some V(III) and V(V) compounds in the HCVS exist amorphously and could not detected by XRD [28].…”

“…The XRD pattern showed in Figure 1a shows that the main crystal structures in the HCVS were Fe 2 O 3 , FeCr 2 O 4 , MgFe 2 O 4 , Fe 2 VO 4 and Fe 2 SiO 4 [27,28,30]. The vanadium and chromium mainly existed as spinel structures (FeCr 2 O 4 and Fe 2 VO 4 ), which are hard to destroy.…”

“…The roasting process is similar to the sodium-roasting process; the vanadium-containing ores are mixed with lime, limestone, and calcium salts at fixed mole ratios and then roasted at high temperatures, which are higher than with sodium roasting. During the roasting process, the vanadium spinel is decomposed and reacted with calcium salts to form different kinds of calciumvanadate, which are determined by the mole ratio of the vanadium to calcium salts [26][27][28][29][30]. Usually, some leaching enhancing processes or multiple roasting processes accompany this process to achieve high recovery [16,[31][32][33][34].…”

Separation of Vanadium and Titanium Phase from the Vanadium Slag System Utilizing Supergravity

“…As the V-spinel particles were wrapped in silicate phase in the vanadium slag, larger grain size and higher spinel grade could increase the exposed area to improve the vanadium oxidation and yield rates during wet extraction process, which could effectively reduce the required sodium salt dosage and roasting temperature as well as waste discharge. [16][17][18][19] Table 3 shows the chemical composition of the stratified sample using XRF and ICP-OES with the G = 700, T = 1 723 K and t = 10 minutes. The mass fraction of V 2 O 3 in the V-enriched slag was up to 32.98 wt%, while that in the Ti-containing slag was just 4.14 wt%, which presented a clear differentiation phenomenon.…”

“…[12][13][14][15] Then, the vanadium oxides in the vanadium slag are treated by wet extraction to obtain V 2 O 5 , but TiO 2 is discharged into the waste residue, which not only leads to resource waste, but also causes environmental pollution. [14][15][16][17][18] Furthermore, the plenty of TiO 2 can significantly improve the chemical stability of the spinel boundary and reduce the conversion rate of vanadium during the salt roasting and leaching. [14][15][16][19][20][21] Therefore, it is necessary to improve the grade of vanadium slag and recycle titanium resource before the vanadium wet extraction process.…”