Study On The Intensification Methods For Hydrometallurgical Leaching Process Of Converter Vanadium Slag

Vanadium is currently defined as a strategic metal that is widely used in many fields, such as the steel, chemical, and aerospace industries, because of its excellent properties. In China, the vanadium slag derived by conversion from hot metal containing vanadium is one of the most important sources of vanadium。Well-known methods that have recently been used to extract vanadium from vanadium slag include blank roasting–acidic leaching, calcium salt roasting–acidic leaching, sodium salt roasting–water leaching, and acidic leaching–solvent extraction. Sodium salt roasting–water leaching technology is comparatively mature and has been applied extensively in many vanadium enterprises. In the roasting process, vanadium slag was oxidized roasted under high temperature in the rotary kiln with the addition of sodium salt(Na Cl 、 Na2CO3), converting low-valent vanadium into water-solube high-valent vanadium(V). However, the resultant low-valent vanadium from insufficient sodium salt oxidation roasting and the vanadium component with a silicon-wrapped structure affect the improvement of vanadium extraction yield, thereby limiting the comprehensive utilization of vanadium resources.To solve above problems, sodium salt converter vanadium slag was taken as the research object, to investigate a most efficient 、 low coast 、 no pollution hydrometallurgical leaching method, by which low-valent vanadium can be converted into water-soluble high-valent vanadium(V) during the leaching process.The research content includes the following two aspects:① Air strengthening of hydrometallurgy process for leaching vanadium from converter slag: Anthraquinone-2,6- disulfonic acid disodium salt(ADA) or tannin as oxygen carrier was added into the water leaching process to transfer oxygen and to strengthen the air oxidation process of low valency vanadium. Phases of reaction system were analyzed using XRD, SEM, UV and UV-Vis DRS. The reaction mechanism of the process was also studied to prove its theoretical feasibility. Low valency vanadium was effectively oxidized by ADA or tannin, and vanadium leaching ratios increased from initial 89.47% to 92.84% and 93.64%, while vanadium contents in th e leaching residue reduced from 1.1% to 0.52% and 0.47%, respectively. It also proved that catalysts had no negative effect on the consequential process.② Hydrometallurgical Leaching Process Intensified by an Electric Field forConverter Vanadium Slag: The mechanism of the electro-oxidation hydrometallurgical leaching process was examined along with the electrochemical performance of the reaction system through X-ray diffraction, scanning electron microscopy, ultraviolet,and ultraviolet–visible diffuse reflectance spectroscopy. Results showed that low-valent vanadium can be oxidized effectively under an electric field in the leaching process. The leaching rate of vanadium reached 93.67% under the optimum conditions, including a current density of 1000 A/m2, a liquid-to-solid ratio of 4:1 ml/g, a temperature of 80 °C,and a leaching time of 40 min. This percentage is 3.73% higher than that attained under the same conditions without an electric field. Meanwhile, the vanadium content in slag decreased from 7.15% to 0.98%.