Enhancement of vanadium extraction at low temperature sodium roasting by electric field and sodium persulfate

Hydrometallurgical leaching process enhanced by electric field coupled with sodium persulfate was developed to improve the leaching efficiency of vanadium. A high vanadium leaching efficiency of 95.64% was achieved under the optimal conditions, including roasting temperature at 650 degrees C, 5 wt% sodium persulfate, current density of 1000 A/m(2), leaching temperature of 60 degrees C, leaching time of 30 min, liquid-solid ratio of 0.5 mL/g. Xray diffraction, X-ray photoelectron spectroscopy and scanning electron microscopy were used to characterize the mechanism. Results indicated that the low-temperature roasting changed the phase of vanadium, while O-2 produced in electric field promoted the chemical conversion and oxidation process. Meanwhile, electric field expedited the collision among the moving particles, therefore it facilitated the dissolution of wrapped vanadium. It also found that electric field and sodium persulfate had synergetical effect on oxidization of low-valent vanadium to high-valence, which made the leaching efficiency increased by 26.94%. A high selective extraction of vanadium was obtained by electro-oxidation leaching with the characteristic diffraction peak of the main phases disappeared in the XRD pattern, while leaving a residue composed primarily of silicon dioxide and iron oxide. These findings could provide guidance for utilization of vanadium slag.